阅读说明：本技术 一种非全线平行四回线路零序分布参数的非解耦测量方法 (Non-decoupling measurement method for zero sequence distribution parameters of non-full-line parallel four-circuit line ) 是由 胡志坚 牟洪江 高明鑫 于 2021-05-28 设计创作，主要内容包括：本申请涉及一种非全线平行四回线路零序分布参数的非解耦测量方法,通过同步测量四回线路在四种测量方式下线路首末端的零序分量计算对应的零序基波分量,以此计算线路传输矩阵,并根据传输矩阵和部分中间变量,逐步求得四回线路全线的零序分布参数。本发明考虑了不同回线路平行时由于电磁耦合关系不同导致线路各段参数不同的情况,符合工程实际,并且克服了线路分布效应的影响,测量精度高。(The application relates to a non-decoupling measurement method for zero-sequence distribution parameters of non-full-line parallel four-circuit lines, which calculates corresponding zero-sequence fundamental wave components by synchronously measuring zero-sequence components of the head and tail ends of the four-circuit lines in four measurement modes, calculates a line transmission matrix according to the zero-sequence fundamental wave components, and gradually obtains the zero-sequence distribution parameters of the full-line of the four-circuit lines according to the transmission matrix and partial intermediate variables. The invention considers the condition that the parameters of each section of the line are different due to different electromagnetic coupling relations when different return lines are parallel, accords with the engineering practice, overcomes the influence of the line distribution effect and has high measurement precision.)

1. A non-decoupling measurement method for zero sequence distribution parameters of a non-full-line parallel four-circuit line is characterized in that the non-full-line parallel four-circuit line is composed of a first power transmission line, a second power transmission line, a third power transmission line and a fourth power transmission line, and the measurement method comprises the following steps:

defining a non-full-line parallel four-loop circuit as a three-section type structure non-full-line parallel four-loop power transmission circuit consisting of a first section of double-loop coupling part circuit, a middle section of four-loop coupling part circuit and a last section of double-loop coupling part circuit, and defining the length of a first power transmission line, the length of a second power transmission line, the length of a third power transmission line and the length of the fourth power transmission line according to the length of the first section of double-loop coupling part circuit, the length of the middle section of four-loop coupling part circuit and the length of the last section of double-loop coupling part circuit to obtain the head end positions and the tail end positions of the first power transmission line, the second power transmission line, the third power transmission line and the fourth power transmission line;

defining four different measurement modes based on the head end positions and the tail end positions of the first power transmission line, the second power transmission line, the third power transmission line and the fourth power transmission line, and acquiring zero sequence components of the first power transmission line, the second power transmission line, the third power transmission line and the fourth power transmission line according to the four different measurement modes in a line power failure state to further calculate corresponding zero sequence fundamental wave components through a Fourier algorithm so as to calculate a line transmission matrix;

and calculating zero-sequence impedance and zero-sequence admittance of the first double-loop characteristic root, the second double-loop characteristic root, the first double-loop coupling part line and the last double-loop coupling part line based on non-zero elements of the line transmission matrix, and then further calculating zero-sequence resistance, zero-sequence inductance and zero-sequence capacitance of the middle four-loop coupling part line.

2. The non-decoupled measurement method of zero-sequence distribution parameters of non-all-line parallel four-circuit lines according to claim 1,

further calculating zero sequence resistance, zero sequence inductance and zero sequence capacitance of the middle section four-circuit coupling part line, comprising the following steps:

calculating a zero-sequence impedance matrix and an admittance matrix of the middle section four-circuit coupling part line based on the first double-circuit characteristic root, the second double-circuit characteristic root, and the zero-sequence impedance and the zero-sequence admittance of the first section double-circuit coupling part line and the last section double-circuit coupling part line;

and calculating the zero sequence resistance, the zero sequence inductance and the zero sequence capacitance of the middle-section four-circuit coupling part circuit according to the zero sequence impedance matrix and the admittance matrix of the middle-section four-circuit coupling part circuit.

3. The non-decoupled measurement method of zero-sequence distribution parameters of non-all-line parallel four-circuit lines according to claim 2,

calculating a zero-sequence impedance matrix and an admittance matrix of the middle section four-circuit coupling part line based on the first double-circuit characteristic root, the second double-circuit characteristic root, the zero-sequence impedance and the zero-sequence admittance of the first section double-circuit coupling part line and the last section double-circuit coupling part line, and the method comprises the following steps:

calculating a first-section double-loop intermediate variable to a sixth first-section double-loop intermediate variable and a first end-section double-loop intermediate variable to a sixth end-section double-loop intermediate variable based on the first double-loop characteristic root, the second double-loop characteristic root, the first-section double-loop coupling part line and the zero-sequence impedance and the zero-sequence admittance of the last-section double-loop coupling part line, and then calculating a first characteristic intermediate variable to an eighth characteristic intermediate variable and a first element intermediate variable to an eighth element intermediate variable by combining non-zero elements of the line transmission matrix;

and calculating a zero sequence impedance matrix and an admittance matrix of the middle section four-circuit coupling part line based on the first characteristic intermediate variable to the eighth characteristic intermediate variable and the first element intermediate variable to the eighth element intermediate variable.

4. The non-decoupled measurement method of zero-sequence distribution parameters of non-all-line parallel four-circuit lines according to claim 3,

calculating a zero sequence impedance matrix and an admittance matrix of the middle section four-circuit coupling part line based on the first characteristic intermediate variable to the eighth characteristic intermediate variable and the first element intermediate variable to the eighth element intermediate variable, comprising the steps of:

calculating a first four-pass feature root to a fourth four-pass feature root according to the first feature intermediate variable to the eighth feature intermediate variable to further calculate a first intermediate substitution variable to a fourth intermediate substitution variable and a first intermediate substitution variable to a fourth intermediate substitution variable, and then combining the first feature intermediate variable to the eighth feature intermediate variable and the first four-pass feature root to the fourth feature root to calculate a first matrix intermediate variable to an eighth matrix intermediate variable;

and calculating a zero sequence impedance matrix and an admittance matrix of the middle-section four-loop coupling part line according to the first element intermediate variable to the eighth element intermediate variable, the first intermediate substitution variable to the fourth intermediate substitution variable, the first fourth-loop characteristic root to the fourth-loop characteristic root and the first matrix intermediate variable to the eighth matrix intermediate variable.

5. The non-decoupled measurement method of zero-sequence distribution parameters of non-full-line parallel four-circuit lines as claimed in any one of claims 1 to 4,

defining the length of a first power transmission line, the length of a second power transmission line, the length of a third power transmission line and the length of a fourth power transmission line according to the length of the first section of double-circuit coupling part line, the length of the middle section of four-circuit coupling part line and the length of the last section of double-circuit coupling part line, and comprising the following steps:

defining the length of the first transmission line as l₁+l₂+l₃The second transmission line has a length of l₁+l₂+l₃And the third transmission line has a length of l₂The fourth transmission line has a length of l₂Wherein l is₁The first section of the double-loop coupling part has a line length of l₂The line length of the middle section four-loop coupling part, l₃The line length of the tail section double-loop coupling part.

6. The non-decoupled measurement method of zero-sequence distribution parameters of non-all-line parallel four-circuit lines according to claim 5,

the four different measurement modes include:

the method comprises the following steps that a first measurement mode is that a single-phase power supply is added at the head end of a first power transmission line, the tail end of the first power transmission line is grounded, the head end and the tail end of a second power transmission line are grounded, the head end of a third power transmission line is suspended, the tail end of the third power transmission line is grounded, and the head end of a fourth power transmission line is suspended, and the tail end of the fourth power transmission line is grounded;

the first measurement mode is that the head end of the first power transmission line is suspended, the tail end of the first power transmission line is grounded, the head end of the second power transmission line is suspended, the tail end of the second power transmission line is grounded, the head end of the third power transmission line is provided with a single-phase power supply, the tail end of the third power transmission line is grounded, and the head end and the tail end of the fourth power transmission line are both grounded;

a third measurement mode, wherein the third measurement mode is that the head end of the first power transmission line is added with a single-phase power supply, and the tail end of the first power transmission line is suspended, the head end of the second power transmission line is grounded, and the tail end of the second power transmission line is suspended, the head end of the third power transmission line is grounded, and the tail end of the third power transmission line is suspended, and the head end of the fourth power transmission line is grounded, and the tail end of the fourth power transmission line is suspended;

and a fourth measurement mode, wherein the fourth measurement mode is that the head end of the first transmission line is grounded and the tail end of the first transmission line is suspended, the head end of the second transmission line is grounded and the tail end of the second transmission line is suspended, the head end of the third transmission line is provided with a single-phase power supply and the tail end of the third transmission line is suspended, and the head end of the fourth transmission line is grounded and the tail end of the fourth transmission line is suspended.

7. The non-decoupled measurement method of zero-sequence distribution parameters of non-all-line parallel four-circuit lines according to claim 6,

acquiring zero sequence components of the first transmission line, the second transmission line, the third transmission line and the fourth transmission line according to four different measurement modes in a line power failure state, wherein the method comprises the following steps:

and synchronously measuring by using a synchronous measuring device under the power failure state of the line:

zero sequence voltage and zero sequence current of the head end and the tail end of the first power transmission line under the four different measurement modes;

zero sequence voltage and zero sequence current of the head end and the tail end of the second power transmission line under the four different measurement modes;

zero sequence voltage and zero sequence current of the head end and the tail end of the third power transmission line under the four different measurement modes;

and the zero sequence voltage and the zero sequence current of the head end and the tail end of the fourth transmission line under the four different measurement modes.

8. The non-decoupled measurement method of zero-sequence distribution parameters of non-all-line parallel four-circuit lines according to claim 7,

the line transmission matrix is:

wherein, T_mnElements representing the row a, column b of the transmission matrix, a ∈ [1,8 ]]，b∈[1,8]；

The non-zero elements of the line transmission matrix are:

and the number of the first and second electrodes,

and the number of the first and second electrodes,

is the zero sequence fundamental voltage at the head end of the first transmission line in the kth measurement mode,

is the zero sequence fundamental current at the head end of the first transmission line in the kth measurement mode,

is the zero sequence fundamental voltage at the head end of the second transmission line in the kth measurement mode,

is the zero sequence fundamental current at the head end of the second transmission line in the kth measurement mode,

is the zero sequence fundamental voltage at the head end of the third transmission line in the kth measurement mode,

is the zero sequence fundamental current at the head end of the third transmission line in the kth measurement mode,

is the zero sequence fundamental voltage at the head end of the fourth transmission line in the kth measurement mode,

is the zero sequence fundamental current at the head end of the fourth transmission line in the kth measurement mode,

for the zero sequence fundamental voltage at the end of the first transmission line in the kth measurement mode,

is the zero sequence fundamental current at the tail end of the first transmission line in the kth measurement mode,

for the zero sequence fundamental voltage at the end of the second transmission line in the kth measurement mode,

is the zero sequence fundamental current at the tail end of the second transmission line in the kth measurement mode,

for the zero sequence fundamental voltage at the end of the third transmission line in the kth measurement mode,

is the zero sequence fundamental current at the tail end of the third transmission line in the kth measurement mode,

for the zero sequence fundamental voltage at the end of the fourth transmission line in the kth measurement mode,

is zero sequence fundamental current at the tail end of a fourth transmission line in a kth measurement mode, wherein k belongs to [1,4]]。

9. The non-decoupled measurement method of zero-sequence distribution parameters of non-all-parallel four-circuit lines according to claim 8,

calculating zero-sequence impedance and zero-sequence admittance of the first double-loop characteristic root, the second double-loop characteristic root, the first double-loop coupling part line and the last double-loop coupling part line based on non-zero elements of the line transmission matrix, and comprising the following steps:

calculating the zero-sequence impedance and the zero-sequence admittance of the first double-circuit characteristic root, the second double-circuit characteristic root, the first double-circuit coupling part line and the last double-circuit coupling part line according to a first formula,

the first formula is:

in the formula I₁The length of the first-stage double-loop coupling part line, l₃For the length of the end-section double-back-coupled part line, r₁Is the first double-round feature root, r₂Is the second double-loopback feature root, Z_sFor zero sequence self-impedance, Z, of the first double-circuit coupling part line and the last double-circuit coupling part line_mZero-sequence mutual impedance of the first-section double-circuit coupling part line and the last-section double-circuit coupling part line is obtained; y is_sIs the zero sequence self-admittance, Y, of the first-stage double-circuit coupling part line and the last-stage double-circuit coupling part line_mZero sequence mutual admittance of the first section double-circuit coupling part line and the last section double-circuit coupling part line;

calculating zero-sequence resistance, zero-sequence inductance and zero-sequence capacitance of the first-segment double-circuit coupling part line and the last-segment double-circuit coupling part line according to a second formula;

the second formula is:

in the formula, R_sIs the zero sequence self-resistance, L, of the first-stage double-circuit coupling part line and the last-stage double-circuit coupling part line_sZero sequence self inductance C of the first-stage double-circuit coupling part line and the last-stage double-circuit coupling part line_sZero sequence self-capacitance of the first section double-circuit coupling part circuit and the last section double-circuit coupling part circuit; r_mIs the zero sequence mutual resistance, L, of the first-stage double-circuit coupling part line and the last-stage double-circuit coupling part line_mZero sequence mutual inductance of the first double-circuit coupling part line and the last double-circuit coupling part line, C_mThe zero sequence mutual capacitance of the first-segment double-circuit coupling part line and the last-segment double-circuit coupling part line is obtained.

10. The non-decoupled measurement method of zero-sequence distribution parameters of non-all-line parallel four-circuit lines according to claim 9,

further calculating zero sequence resistance, zero sequence inductance and zero sequence capacitance of the middle section four-circuit coupling part line, comprising the following steps:

calculating a first-segment double-loop intermediate variable to a sixth first-segment double-loop intermediate variable and a first-segment double-loop intermediate variable to a sixth tail-segment double-loop intermediate variable according to a third formula;

the third formula is:

in the formula, m₁、n₁、s₁、q₁、h₁、k₁For the c first double-loop intermediate variable, c is equal to [1,6 ]]；m₂、n₂、s₂、q₂、h₂、k₂For the d-th end double-loop intermediate variable, d ∈ [1,6 ]]；

Calculating the first to eighth characteristic intermediate variables and the first to eighth element intermediate variables according to a fourth formula;

the fourth formula is:

in the formula, σ_uvRepresents the e characteristic intermediate variable, e ∈ [1,8 ]]，Represents the f-th element intermediate variable, f ∈ [1,8 ]]，u∈[1,2]，v∈[1,4]；

Calculating a first fourth-turn feature root to a fourth-turn feature root according to a fifth formula;

the fifth formula is:

in the formula I₂For the length of the middle section four-loop coupling part line, p₁Is the first four-pass feature root, p₂Is the second four-pass feature root, p₃Is a third four-round feature root, p₄Is the fourth-round feature root;

calculating first to fourth intermediate replacement variables and first to fourth intermediate replacement variables according to a sixth formula;

the sixth formula is:

in the formula, alpha_gFor the g-th intermediate replacement variable, g ∈ [1,4]]，β_hFor the h-th intermediate substitution variable, h e [1,4]]；

Calculating the intermediate variables from the first matrix to the eighth matrix according to a seventh formula;

the seventh formula is:

in the formula, K_xyRepresents the ith characteristic intermediate variable, i ∈ [1,8 ]]，x∈[1,2]，y∈[1,4]；

Calculating a zero sequence impedance matrix of the middle section four-circuit coupling part line according to an eighth formula;

the eighth formula is:

in the formula, Z_aZero sequence self-impedance Z of four-circuit coupling parts at middle sections of first and second transmission lines_cZero sequence self-impedance, Z, of the middle section four-circuit coupling part of the third transmission line and the fourth transmission line_abIs zero sequence mutual impedance, Z, of the middle section four-loop coupling part of the first transmission line and the second transmission line_acIs zero sequence mutual impedance, Z, of the middle section four-circuit coupling part of the first transmission line and the third transmission line_acAnd simultaneously, the zero sequence mutual impedance, Z, of the middle section four-circuit coupling part of the second transmission line and the fourth transmission line_adIs zero sequence mutual impedance, Z, of middle section four-loop coupling part of the first transmission line and the fourth transmission line_adAnd simultaneously, the zero sequence mutual impedance, Z, of the middle section four-circuit coupling part of the second transmission line and the third transmission line_cdZero sequence mutual impedance of the middle section four-loop coupling parts of the third power transmission line and the fourth power transmission line is obtained;

calculating an admittance matrix of the middle section four-loop coupling part line according to a ninth formula;

the ninth formula is:

in the formula:

in the formula, Y_aIs zero sequence self-admittance, Y, of four-circuit coupling parts at middle sections of a first transmission line and a second transmission line_cZero sequence self-admittance, Y, of four-circuit coupling parts at middle sections of third and fourth transmission lines_abIs zero sequence mutual admittance, Y, of four-circuit coupling parts at the middle sections of the first transmission line and the second transmission line_acIs zero sequence mutual admittance, Y, of four-circuit coupling parts at the middle sections of the first transmission line and the third transmission line_acWhile also delivering a second powerZero sequence mutual admittance, Y, of four-circuit coupling part in middle section of line and fourth power transmission line_adIs zero sequence mutual admittance, Y, of four-circuit coupling parts at middle sections of the first transmission line and the fourth transmission line_adAnd simultaneously, the zero sequence mutual admittance, Y, of the four-circuit coupling part at the middle section of the second transmission line and the third transmission line_cdZero sequence mutual admittance of four-loop coupling parts at the middle sections of a third power transmission line and a fourth power transmission line;

calculating zero sequence resistance, zero sequence inductance and zero sequence capacitance of the middle section four-circuit coupling part line according to a tenth formula;

the tenth formula is:

in the formula, R_aThe zero sequence self-resistance is a zero sequence self-resistance of a four-circuit coupling part at the middle section of the first power transmission line; r_bThe zero sequence self-resistance is the zero sequence self-resistance of the four-circuit coupling part at the middle section of the second power transmission line; r_cThe zero sequence self-resistance of the four-circuit coupling part at the middle section of the third power transmission line; r_dThe zero sequence self-resistance of the four-circuit coupling part at the middle section of the fourth power transmission line; r_abZero-sequence mutual resistance of four-circuit coupling parts at the middle sections of the first power transmission line and the second power transmission line; r_acIs zero sequence mutual resistance, R, of four-circuit coupling parts at the middle sections of the first transmission line and the third transmission line_bdZero-sequence mutual resistance of four-circuit coupling parts at the middle sections of the second power transmission line and the fourth power transmission line; r_adIs zero sequence mutual resistance, R, of four-circuit coupling parts at middle sections of a first power transmission line and a fourth power transmission line_bcZero-sequence mutual resistance of four-circuit coupling parts at the middle sections of the second power transmission line and the third power transmission line; r_cdZero-sequence mutual resistance of four-circuit coupling parts at the middle sections of the third power transmission line and the fourth power transmission line;

L_aa four-loop coupling part at the middle section of the first power transmission linePartial zero sequence self inductance; l is_bThe zero sequence self-inductance is the zero sequence self-inductance of the four-circuit coupling part at the middle section of the second power transmission line; l is_cThe zero sequence self-inductance is the zero sequence self-inductance of the four-circuit coupling part at the middle section of the third power transmission line; l is_dThe zero sequence self-inductance is the zero sequence self-inductance of the four-circuit coupling part at the middle section of the fourth power transmission line; l is_abZero sequence mutual inductance of four-circuit coupling parts at the middle sections of the first power transmission line and the second power transmission line is obtained; l is_acZero sequence mutual inductance L of four-circuit coupling parts at middle sections of the first transmission line and the third transmission line_bdZero sequence mutual inductance of four-circuit coupling parts at the middle sections of the second power transmission line and the fourth power transmission line is obtained; l is_adIs zero sequence mutual inductance of four-circuit coupling parts at the middle sections of the first transmission line and the fourth transmission line, L_bcZero sequence mutual inductance of four-circuit coupling parts at the middle sections of the second power transmission line and the third power transmission line is obtained; l is_cdZero sequence mutual inductance of four-circuit coupling parts at the middle sections of the third power transmission line and the fourth power transmission line is obtained;

C_athe zero sequence self-capacitance is a zero sequence self-capacitance of the four-circuit coupling part at the middle section of the first power transmission line; c_bThe zero sequence self-capacitance is a zero sequence self-capacitance of the four-circuit coupling part at the middle section of the second power transmission line; c_cThe zero sequence self-capacitance is a zero sequence self-capacitance of the four-circuit coupling part at the middle section of the third power transmission line; c_dThe zero sequence self-capacitance is a zero sequence self-capacitance of the four-circuit coupling part at the middle section of the fourth power transmission line; c_abZero sequence mutual capacitance of four-circuit coupling parts at the middle sections of the first transmission line and the second transmission line; c_acZero sequence mutual capacitance C of four-circuit coupling parts at middle sections of the first transmission line and the third transmission line_bdZero-sequence mutual capacitance of four-circuit coupling parts at the middle sections of the second power transmission line and the fourth power transmission line; c_adZero sequence mutual capacitance C of four-circuit coupling parts at middle sections of the first transmission line and the fourth transmission line_bcZero-sequence mutual capacitance of four-circuit coupling parts at the middle sections of the second power transmission line and the third power transmission line; c_cdAnd the zero sequence mutual capacitance of the four-circuit coupling parts at the middle sections of the third transmission line and the fourth transmission line is obtained.

Technical Field

The invention relates to the technical field of power system measurement, in particular to a non-decoupling measurement method for zero-sequence distribution parameters of non-full-line parallel four-circuit lines.

Background

The transmission line parameters have important significance for numerical analysis of the transmission line model, and are widely applied to the fields of power flow calculation, fault analysis, protection setting, fault distance measurement and the like of a power system. Because the complex situation in the process of line erection is difficult to be completely considered in theoretical calculation, parameters of the overhead transmission line specified by Chinese electric power industry standards and a plurality of relevant regulations must be obtained through actual measurement.

In recent years, due to the shortage of land resources, a parallel multi-circuit transmission line shared transmission corridor represented by a same-tower four-circuit transmission line and a non-full-circuit parallel mixed-voltage four-circuit transmission line becomes an effective way for solving the contradiction between transmission engineering construction and land resources.

For the mixed-voltage four-circuit power transmission line which is not parallel to the full line, the related traditional measurement technology is based on a centralized parameter model, the error is large when a long line is measured, and only one parameter can be measured each time, so that the operation steps are complicated and the efficiency is low. In addition, the related traditional measurement technology does not consider the situation that parameters of all sections of the line are different due to different electromagnetic couplings of all sections of the line in the non-full-line parallel four-circuit line, and the probability that the measurement result is seriously inconsistent with the actual situation is high. Recently, a related novel measurement technology for the distribution parameters of a 'two-section' non-full-line parallel four-circuit transmission line has appeared, but the technology is only suitable for a 'two-section' structure line, is not suitable for a 'three-section' structure line, and cannot be used for measuring the zero sequence parameters of a 'three-section' non-full-line parallel mixed-voltage four-circuit line.

Disclosure of Invention

The embodiment of the invention provides a non-decoupling measurement method for zero-sequence distribution parameters of non-full-parallel four-circuit lines, which aims to solve the problem that the related technology can not accurately measure the line parameters of a three-section type line structure.

The invention provides a non-decoupling measurement method for zero sequence distribution parameters of a non-full-line parallel four-circuit line, which is characterized in that the non-full-line parallel four-circuit line is composed of a first power transmission line, a second power transmission line, a third power transmission line and a fourth power transmission line, and the measurement method comprises the following steps:

defining a non-full-line parallel four-loop circuit as a three-section type structure non-full-line parallel four-loop power transmission circuit consisting of a first section of double-loop coupling part circuit, a middle section of four-loop coupling part circuit and a last section of double-loop coupling part circuit, and defining a first power transmission circuit length, a second power transmission circuit length, a third power transmission circuit length and a fourth power transmission circuit length according to the first section of double-loop coupling part circuit length, the middle section of four-loop coupling part circuit length and the last section of double-loop coupling part circuit length to obtain the head end positions and the tail end positions of the first power transmission circuit, the second power transmission circuit, the third power transmission circuit and the fourth power transmission circuit;

defining four different measurement modes based on the head end positions and the tail end positions of the first power transmission line, the second power transmission line, the third power transmission line and the fourth power transmission line, and acquiring zero sequence components of the first power transmission line, the second power transmission line, the third power transmission line and the fourth power transmission line according to the four different measurement modes in a line power failure state so as to further calculate corresponding zero sequence fundamental wave components through a Fourier algorithm, thereby calculating a line transmission matrix;

and calculating zero-sequence impedance and zero-sequence admittance of the first double-loop characteristic root, the second double-loop characteristic root, the first double-loop coupling part line and the last double-loop coupling part line based on non-zero elements of the line transmission matrix, and then further calculating zero-sequence resistance, zero-sequence inductance and zero-sequence capacitance of the middle four-loop coupling part line.

In some embodiments, further calculating a zero-sequence resistance, a zero-sequence inductance, and a zero-sequence capacitance of the middle-section four-circuit coupling part line includes the steps of:

calculating a zero-sequence impedance matrix and an admittance matrix of the middle section four-circuit coupling part line based on the first double-circuit characteristic root, the second double-circuit characteristic root, and the zero-sequence impedance and the zero-sequence admittance of the first section double-circuit coupling part line and the last section double-circuit coupling part line;

and calculating the zero sequence resistance, the zero sequence inductance and the zero sequence capacitance of the middle-section four-circuit coupling part circuit according to the zero sequence impedance matrix and the admittance matrix of the middle-section four-circuit coupling part circuit.

In some embodiments, calculating a zero-sequence impedance matrix and an admittance matrix of the middle-section four-circuit coupling part line based on the first double-circuit characteristic root, the second double-circuit characteristic root, and the zero-sequence impedances and zero-sequence admittances of the first-section double-circuit coupling part line and the last-section double-circuit coupling part line includes:

calculating a first-section double-loop intermediate variable to a sixth first-section double-loop intermediate variable and a first end-section double-loop intermediate variable to a sixth end-section double-loop intermediate variable based on the first double-loop characteristic root, the second double-loop characteristic root, the first-section double-loop coupling part line and the zero-sequence impedance and the zero-sequence admittance of the last-section double-loop coupling part line, and then calculating a first characteristic intermediate variable to an eighth characteristic intermediate variable and a first element intermediate variable to an eighth element intermediate variable by combining non-zero elements of the line transmission matrix;

and calculating a zero sequence impedance matrix and an admittance matrix of the middle section four-circuit coupling part line based on the first characteristic intermediate variable to the eighth characteristic intermediate variable and the first element intermediate variable to the eighth element intermediate variable.

In some embodiments, calculating a zero sequence impedance matrix and an admittance matrix of the middle section four-circuit coupling part line based on the first to eighth characteristic intermediate variables and the first to eighth element intermediate variables includes:

calculating first four-turn feature roots to fourth four-turn feature roots according to the first feature intermediate variables to eighth feature intermediate variables to further calculate first intermediate replacement variables to fourth intermediate replacement variables and first intermediate replacement variables to fourth intermediate replacement variables, and then combining the first feature intermediate variables to eighth feature intermediate variables and the first four-turn feature roots to fourth feature roots to calculate first matrix intermediate variables to eighth matrix intermediate variables;

and calculating a zero sequence impedance matrix and an admittance matrix of the middle-section four-loop coupling part line according to the first element intermediate variable to the eighth element intermediate variable, the first intermediate substitution variable to the fourth intermediate substitution variable, the first fourth-loop feature root to the fourth-loop feature root and the first matrix intermediate variable to the eighth matrix intermediate variable.

In some embodiments, defining a first transmission line length, a second transmission line length, a third transmission line length, and a fourth transmission line length according to the first-segment double-loop coupling part line length, the middle-segment four-loop coupling part line length, and the last-segment double-loop coupling part line length includes:

defining the length of the first transmission line as l₁+l₂+l₃The second transmission line has a length of l₁+l₂+l₃And the third transmission line has a length of l₂The fourth transmission line has a length of l₂Wherein l is₁The first section of the double-loop coupling part has a line length of l₂The line length of the middle section four-loop coupling part, l₃The line length of the tail section double-loop coupling part is adopted.

In some embodiments, the four different measurement modes include:

the method comprises the following steps that a first measurement mode is that a single-phase power supply is added at the head end of a first power transmission line, the tail end of the first power transmission line is grounded, the head end and the tail end of a second power transmission line are grounded, the head end of a third power transmission line is suspended, the tail end of the third power transmission line is grounded, and the head end of a fourth power transmission line is suspended, and the tail end of the fourth power transmission line is grounded;

the first measurement mode is that the head end of the first power transmission line is suspended, the tail end of the first power transmission line is grounded, the head end of the second power transmission line is suspended, the tail end of the second power transmission line is grounded, the head end of the third power transmission line is provided with a single-phase power supply, the tail end of the third power transmission line is grounded, and the head end and the tail end of the fourth power transmission line are both grounded;

a third measurement mode, wherein the third measurement mode is that the head end of the first power transmission line is added with a single-phase power supply, and the tail end of the first power transmission line is suspended, the head end of the second power transmission line is grounded, and the tail end of the second power transmission line is suspended, the head end of the third power transmission line is grounded, and the tail end of the third power transmission line is suspended, and the head end of the fourth power transmission line is grounded, and the tail end of the fourth power transmission line is suspended;

and a fourth measurement mode, wherein the fourth measurement mode is that the head end of the first transmission line is grounded and the tail end of the first transmission line is suspended, the head end of the second transmission line is grounded and the tail end of the second transmission line is suspended, the head end of the third transmission line is provided with a single-phase power supply and the tail end of the third transmission line is suspended, and the head end of the fourth transmission line is grounded and the tail end of the fourth transmission line is suspended.

In some embodiments, the obtaining zero sequence components of the first transmission line, the second transmission line, the third transmission line, and the fourth transmission line according to four different measurement modes in a line power outage state includes:

and synchronously measuring by using a synchronous measuring device under the power failure state of the line:

zero sequence voltage and zero sequence current of the head end and the tail end of the first power transmission line under the four different measurement modes;

zero sequence voltage and zero sequence current of the head end and the tail end of the second power transmission line under the four different measurement modes;

zero sequence voltage and zero sequence current of the head end and the tail end of the third power transmission line under the four different measurement modes;

and the zero sequence voltage and the zero sequence current of the head end and the tail end of the fourth transmission line under the four different measurement modes.

In some embodiments, the line transmission matrix is:

wherein, T_mnElements representing the row a, column b of the transmission matrix, a ∈ [1,8 ]]，b∈[1,8]；

The non-zero elements of the line transmission matrix are:

and the number of the first and second electrodes,

and the number of the first and second electrodes,

is the zero sequence fundamental voltage at the head end of the first transmission line in the kth measurement mode,

is the zero sequence fundamental current at the head end of the first transmission line in the kth measurement mode,

is the zero sequence fundamental voltage at the head end of the second transmission line in the kth measurement mode,

is the zero sequence fundamental current at the head end of the second transmission line in the kth measurement mode,

is the zero sequence fundamental voltage at the head end of the third transmission line in the kth measurement mode,

is the zero sequence fundamental current at the head end of the third transmission line in the kth measurement mode,

is the zero sequence fundamental voltage at the head end of the fourth transmission line in the kth measurement mode,

is the zero sequence fundamental current at the head end of the fourth transmission line in the kth measurement mode,

for the zero sequence fundamental voltage at the end of the first transmission line in the kth measurement mode,

is the zero sequence fundamental current at the tail end of the first transmission line in the kth measurement mode,

for the zero sequence fundamental voltage at the end of the second transmission line in the kth measurement mode,

is the zero sequence fundamental current at the tail end of the second transmission line in the kth measurement mode,

for the zero sequence fundamental voltage at the end of the third transmission line in the kth measurement mode,

is the zero sequence fundamental current at the tail end of the third transmission line in the kth measurement mode,

for the zero sequence fundamental voltage at the end of the fourth transmission line in the kth measurement mode,

is zero sequence fundamental current at the tail end of a fourth transmission line in a kth measurement mode, wherein k belongs to [1,4]]。

In some embodiments, calculating the zero-sequence impedance and the zero-sequence admittance of the first double-loop characteristic root, the second double-loop characteristic root, the first double-loop coupling section line and the last double-loop coupling section line based on the non-zero elements of the line transmission matrix comprises:

calculating the zero-sequence impedance and the zero-sequence admittance of the first double-circuit characteristic root, the second double-circuit characteristic root, the first double-circuit coupling part line and the last double-circuit coupling part line according to a first formula,

the first formula is:

in the formula I₁The length of the first-stage double-loop coupling part line, l₃For the length of the end-section double-back-coupled part line, r₁Is the first double-round feature root, r₂Is the second double-loopback feature root, Z_sFor zero sequence self-impedance, Z, of the first double-circuit coupling part line and the last double-circuit coupling part line_mZero-sequence mutual impedance of the first-section double-circuit coupling part line and the last-section double-circuit coupling part line is obtained; y is_sIs the zero sequence self-admittance, Y, of the first-stage double-circuit coupling part line and the last-stage double-circuit coupling part line_mZero sequence mutual admittance of the first section double-circuit coupling part line and the last section double-circuit coupling part line;

calculating zero sequence resistance, zero sequence inductance and zero sequence capacitance of the first section of double-circuit coupling part circuit and the last section of double-circuit coupling part circuit according to a second formula;

the second formula is:

in the formula, R_sIs a headZero sequence self-resistance, L, of the line of the segment double-loop coupling part and the line of the end segment double-loop coupling part_sIs zero sequence self inductance, C of the first-stage double-circuit coupling part line and the last-stage double-circuit coupling part line_sZero-sequence self-capacitance of the first-segment double-circuit coupling part line and the last-segment double-circuit coupling part line; r_mIs the zero-sequence mutual resistance, L, of the first-stage double-circuit coupling part line and the last-stage double-circuit coupling part line_mZero-order mutual inductance of the first-stage double-circuit coupling part line and the last-stage double-circuit coupling part line, C_mThe zero-sequence mutual capacitance of the first-segment double-loop coupling part line and the last-segment double-loop coupling part line is obtained.

In some embodiments, further calculating a zero-sequence resistance, a zero-sequence inductance, and a zero-sequence capacitance of the middle-section four-circuit coupling part line includes the steps of:

calculating a first-section double-circuit intermediate variable to a sixth first-section double-circuit intermediate variable and a first-end-section double-circuit intermediate variable to a sixth end-section double-circuit intermediate variable according to a third formula;

the third formula is:

in the formula, m₁、n₁、s₁、q₁、h₁、k₁For the c first double-loop intermediate variable, c is equal to [1,6 ]]； m₂、n₂、s₂、q₂、h₂、k₂For the d-th end double-loop intermediate variable, d ∈ [1,6 ]]；

Calculating first to eighth characteristic intermediate variables and first to eighth element intermediate variables according to a fourth formula;

the fourth formula is:

in the formula, σ_uvRepresents the e characteristic intermediate variable, e ∈ [1,8 ]]，Represents the intermediate variable in the f-th element, f ∈ [1,8 ]]，u∈[1,2]，v∈[1,4]；

Calculating a first fourth-turn feature root to a fourth-turn feature root according to a fifth formula;

the fifth formula is:

in the formula I₂For the length of the middle section four-loop coupling part line, p₁Is the first four-pass feature root, p₂Is the second four-pass feature root, p₃Is a third four-round feature root, p₄Is the fourth-round feature root;

calculating first to fourth intermediate replacement variables and first to fourth intermediate replacement variables according to a sixth formula;

the sixth formula is:

in the formula, alpha_gFor the g-th intermediate replacement variable, g ∈ [1,4]]，β_hFor the h-th intermediate substitution variable, h e [1,4]]；

Calculating the intermediate variables from the first matrix to the eighth matrix according to a seventh formula;

the seventh formula is:

in the formula, K_xyRepresents the ith characteristic intermediate variable, i ∈ [1,8 ]]，x∈[1,2]，y∈[1,4]；

Calculating a zero sequence impedance matrix of the middle section four-circuit coupling part line according to an eighth formula;

the eighth formula is:

in the formula, Z_aZero sequence self-impedance Z of four-circuit coupling parts at middle sections of first and second transmission lines_cZero sequence self-impedance, Z, of the middle section four-circuit coupling part of the third transmission line and the fourth transmission line_abZero sequence mutual impedance, Z, of the middle four-circuit coupling part of the first transmission line and the second transmission line_acIs zero sequence mutual impedance, Z, of the middle section four-circuit coupling part of the first transmission line and the third transmission line_acAnd simultaneously, the zero sequence mutual impedance, Z, of the middle section four-circuit coupling part of the second transmission line and the fourth transmission line_adIs zero sequence mutual impedance, Z, of middle-section four-loop coupling parts of the first transmission line and the fourth transmission line_adAt the same timeAlso is zero sequence mutual impedance, Z, of the middle section four-circuit coupling part of the second transmission line and the third transmission line_cdZero-sequence mutual impedance of four-loop coupling parts at the middle sections of the third transmission line and the fourth transmission line is obtained;

calculating an admittance matrix of the middle section four-loop coupling part line according to a ninth formula;

the ninth formula is:

in the formula:

in the formula, Y_aIs zero sequence self-admittance, Y, of four-circuit coupling parts at middle sections of a first transmission line and a second transmission line_cZero sequence self-admittance, Y, of four-circuit coupling parts at middle sections of third and fourth transmission lines_abIs zero sequence mutual admittance, Y, of four-circuit coupling parts at the middle sections of the first transmission line and the second transmission line_acIs zero sequence mutual admittance, Y, of four-circuit coupling parts at the middle sections of the first transmission line and the third transmission line_acAnd simultaneously, the zero sequence mutual admittance, Y, of the four-circuit coupling part at the middle section of the second transmission line and the fourth transmission line_adIs zero sequence mutual admittance, Y, of four-circuit coupling parts at middle sections of the first transmission line and the fourth transmission line_adAnd simultaneously, the zero sequence mutual admittance, Y, of the four-circuit coupling part at the middle section of the second transmission line and the third transmission line_cdZero sequence mutual admittance of four-loop coupling parts at the middle sections of a third power transmission line and a fourth power transmission line;

calculating zero sequence resistance, zero sequence inductance and zero sequence capacitance of the middle section four-circuit coupling part line according to a tenth formula;

the tenth formula is:

in the formula, R_aThe zero sequence self-resistance is a zero sequence self-resistance of a four-circuit coupling part at the middle section of the first power transmission line; r_bThe zero sequence self-resistance is the zero sequence self-resistance of the four-circuit coupling part at the middle section of the second power transmission line; r_cThe zero sequence self-resistance of the four-circuit coupling part at the middle section of the third power transmission line; r_dThe zero sequence self-resistance of the four-circuit coupling part at the middle section of the fourth power transmission line; r_abZero-sequence mutual resistance of four-circuit coupling parts at the middle sections of the first power transmission line and the second power transmission line; r_acIs zero sequence mutual resistance, R, of four-circuit coupling parts at the middle sections of the first transmission line and the third transmission line_bdZero-sequence mutual resistance of four-circuit coupling parts at the middle sections of the second power transmission line and the fourth power transmission line; r_adIs zero sequence mutual resistance, R, of four-circuit coupling parts at middle sections of a first power transmission line and a fourth power transmission line_bcZero-sequence mutual resistance of four-circuit coupling parts at the middle sections of the second power transmission line and the third power transmission line; r_cdZero-sequence mutual resistance of four-circuit coupling parts at the middle sections of the third power transmission line and the fourth power transmission line;

L_athe zero sequence self-inductance is a zero sequence self-inductance of a four-circuit coupling part at the middle section of the first power transmission line; l is_bThe zero sequence self-inductance is the zero sequence self-inductance of the four-circuit coupling part in the middle section of the second power transmission line; l is_cThe zero sequence self-inductance is the zero sequence self-inductance of the four-turn coupling part at the middle section of the third power transmission line; l is_dThe zero sequence self-inductance is the zero sequence self-inductance of the four-circuit coupling part at the middle section of the fourth power transmission line; l is_abZero sequence mutual inductance of four-circuit coupling parts at the middle sections of the first power transmission line and the second power transmission line is obtained; l is_acZero sequence mutual inductance L of four-circuit coupling parts at middle sections of the first transmission line and the third transmission line_bdZero sequence mutual inductance of four-circuit coupling parts at the middle sections of the second power transmission line and the fourth power transmission line is obtained; l is_adIs zero sequence mutual inductance of four-circuit coupling parts at the middle sections of the first transmission line and the fourth transmission line, L_bcZero sequence mutual inductance of four-circuit coupling parts at the middle sections of the second power transmission line and the third power transmission line is obtained; l is_cdZero sequence mutual inductance of four-circuit coupling parts at the middle sections of the third power transmission line and the fourth power transmission line is obtained;

C_athe zero sequence self-capacitance is a zero sequence self-capacitance of the four-circuit coupling part at the middle section of the first power transmission line; c_bThe zero sequence self-capacitance is a zero sequence self-capacitance of the four-circuit coupling part at the middle section of the second transmission line; c_cThe zero sequence self-capacitance is the zero sequence self-capacitance of the four-circuit coupling part at the middle section of the third power transmission line; c_dThe zero sequence self-capacitance is a zero sequence self-capacitance of the four-circuit coupling part at the middle section of the fourth power transmission line; c_abZero sequence mutual capacitance of four-circuit coupling parts at the middle sections of the first transmission line and the second transmission line; c_acZero sequence mutual capacitance C of four-circuit coupling parts at middle sections of the first transmission line and the third transmission line_bdZero-sequence mutual capacitance of four-circuit coupling parts at the middle sections of the second power transmission line and the fourth power transmission line; c_adZero sequence mutual capacitance C of four-circuit coupling parts at middle sections of the first transmission line and the fourth transmission line_bcZero-sequence mutual capacitance of four-circuit coupling parts at the middle sections of the second power transmission line and the third power transmission line; c_cdAnd the zero sequence mutual capacitance of the four-circuit coupling parts at the middle sections of the third transmission line and the fourth transmission line is obtained.

The embodiment considers the condition that parameters of each section of a line are different due to different electromagnetic couplings of each section of the line of a non-full-line parallel four-circuit power transmission line, provides a zero-sequence distribution parameter non-decoupling accurate measurement method suitable for a three-section non-full-line parallel four-circuit power transmission line based on a distribution parameter model, fills the blank that the zero-sequence distribution parameter of the two-section non-full-line parallel four-circuit power transmission line can only be measured by the existing method, overcomes the defect that the measurement error is large due to the fact that a long line is measured by a traditional method based on a centralized parameter model, and compared with the traditional measurement method which needs 12 measurement methods, the method provided by the embodiment only needs 4 measurement methods, can measure a plurality of zero-sequence parameters of zero-sequence resistance, zero-sequence inductance and zero-sequence capacitance at one time, and has the measurement accuracy far higher than the traditional measurement method which can only measure one zero-sequence parameter at a time, the requirement of engineering actual design is met. Meanwhile, the method is suitable for three-section type non-full-line parallel four-circuit transmission lines under any mixed voltage condition, is suitable for zero-sequence distribution parameter measurement of three-section type non-full-line parallel mixed voltage four-circuit alternating current transmission lines, and is also suitable for zero-sequence distribution parameter measurement of three-section type non-full-line parallel double-circuit bipolar direct current transmission lines which may appear in the future.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a physical model diagram of a three-section type non-full-line parallel mixed-voltage four-circuit transmission line according to an embodiment of the present invention;

fig. 2 is a simulation model diagram of a three-segment type non-full-line parallel mixed-voltage four-circuit transmission line according to an embodiment of the present invention;

fig. 3 is a comparison graph of measurement errors of the middle section four-loop coupling portion provided by the embodiment of the present invention when the line length is unchanged and the conventional method;

fig. 4 is a comparison graph of the measurement error of the first-stage double-loop coupling part and the last-stage double-loop coupling part provided by the embodiment of the invention when the line length is unchanged and the traditional method.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The embodiment of the invention provides a non-decoupling measurement method for zero sequence distribution parameters of a non-full-line parallel four-circuit line, which is characterized in that the non-full-line parallel four-circuit line is composed of a first transmission line, a second transmission line, a third transmission line and a fourth transmission line, and the measurement method comprises the following steps: defining a non-full-line parallel four-loop circuit as a three-section type structure non-full-line parallel four-loop transmission circuit consisting of a first section of double-loop coupling part circuit, a middle section of four-loop coupling part circuit and a last section of double-loop coupling part circuit, and defining the length of a first transmission line, the length of a second transmission line, the length of a third transmission line and the length of the fourth transmission line according to the length of the first section of double-loop coupling part circuit, the length of the middle section of four-loop coupling part circuit and the length of the last section of double-loop coupling part circuit to obtain the head ends and the tail ends of the first transmission line, the second transmission line, the third transmission line and the fourth transmission line;

defining four different measurement modes based on the head end positions and the tail end positions of the first power transmission line, the second power transmission line, the third power transmission line and the fourth power transmission line, and acquiring zero sequence components of the first power transmission line, the second power transmission line, the third power transmission line and the fourth power transmission line according to the four different measurement modes in a line power failure state so as to further calculate corresponding zero sequence fundamental wave components through a Fourier algorithm, thereby calculating a line transmission matrix;

and calculating zero-sequence impedance and zero-sequence admittance of the first double-loop characteristic root, the second double-loop characteristic root, the first double-loop coupling part line and the last double-loop coupling part line based on non-zero elements of the line transmission matrix, and then further calculating zero-sequence resistance, zero-sequence inductance and zero-sequence capacitance of the middle four-loop coupling part line.

The embodiment considers the condition that parameters of each section of a line are different due to different electromagnetic couplings of each section of the line of a non-full-line parallel four-circuit power transmission line, provides a zero-sequence distribution parameter non-decoupling accurate measurement method suitable for a three-section non-full-line parallel four-circuit power transmission line based on a distribution parameter model, fills the blank that zero-sequence distribution parameters of a two-section non-full-line parallel mixed-compression four-circuit power transmission line can only be measured by the conventional method, overcomes the defect that a great measurement error is caused by measuring a long line by the conventional method based on a centralized parameter model, needs 12 measurement modes in comparison with the conventional measurement method, only needs 4 measurement modes, can measure a plurality of zero-sequence parameters of zero-sequence resistance, zero-sequence inductance and zero-sequence capacitance at one time, and has measurement accuracy far higher than that of the conventional measurement method which can only measure one zero-sequence parameter at a time, the requirement of engineering actual design is met. Meanwhile, the method is suitable for three-section type non-full-line parallel four-circuit transmission lines under any mixed voltage condition, is suitable for zero-sequence distribution parameter measurement of three-section type non-full-line parallel mixed voltage four-circuit alternating current transmission lines, and is also suitable for zero-sequence distribution parameter measurement of three-section type non-full-line parallel double-circuit bipolar direct current transmission lines which may appear in the future.

In a specific embodiment, the method for accurately measuring the zero sequence distribution parameters of the three-section type non-full-line parallel mixed-voltage four-circuit transmission line comprises the following steps:

step 1, defining the length of a first power transmission line, the length of a second power transmission line, the length of a third power transmission line and the length of a fourth power transmission line, wherein the first power transmission line, the second power transmission line, the third power transmission line and the fourth power transmission line are four-circuit non-full-line parallel power transmission lines under a three-section structure; defining the line length of a first section of four-loop coupling part, the line length of a middle section of double-loop coupling part and the line length of a last section of four-loop coupling part, wherein the first section of double-loop coupling part, the middle section of four-loop coupling part and the last section of double-loop coupling part are three parts of a three-section type non-full-line parallel four-loop power transmission line;

the first transmission line, the second transmission line, the third transmission line and the fourth transmission line are shown in figure 1.

Step 1, defining a three-section type non-full-line parallel mixed-compression four-circuit line as follows:

the length of the first transmission line is l₁+l₂+l₃；

The length of the second transmission line is l₁+l₂+l₃；

The length of the third transmission line is l₂；

The length of the fourth transmission line is l₂；

The length from the head end of the first-section double-circuit coupling part line to the tail end of the first-section double-circuit coupling part line is l₁；

The length from the head end of the middle section four-loop coupling part line to the tail end of the middle section four-loop coupling part line is l₂；

The length from the head end of the last double-circuit coupling part line to the tail end of the last double-circuit coupling part line is l₃；

Step 2, defining a first measurement mode, a second measurement mode, a third measurement mode and a fourth measurement mode;

step 2, the first measurement mode is as follows:

a single-phase power supply is added at the head end of the first power transmission line, and the tail end of the first power transmission line is grounded; the head end of the second power transmission line is grounded, and the tail end of the second power transmission line is grounded; the head end of the third power transmission line is suspended, and the tail end of the third power transmission line is grounded; the head end of the fourth transmission line is suspended, and the tail end of the fourth transmission line is grounded;

step 2, the second measurement mode is as follows:

the head end of the first power transmission line is suspended, and the tail end of the first power transmission line is grounded; the head end of the second transmission line is suspended, and the tail end of the second transmission line is grounded; a single-phase power supply is added at the head end of the third power transmission line, and the tail end of the third power transmission line is grounded; the head end of the fourth power transmission line is grounded, and the tail end of the fourth power transmission line is grounded;

step 2, the third measurement mode is as follows:

a single-phase power supply is added at the head end of the first power transmission line, and the tail end of the first power transmission line is suspended; the head end of the second power transmission line is grounded, and the tail end of the second power transmission line is suspended; the head end of the third power transmission line is grounded, and the tail end of the third power transmission line is suspended; the head end of the fourth transmission line is grounded, and the tail end of the fourth transmission line is suspended;

step 2, the fourth measurement mode is as follows:

the head end of the first power transmission line is grounded, and the tail end of the first power transmission line is suspended; the head end of the second transmission line is grounded, and the tail end of the second transmission line is suspended; a single-phase power supply is added at the head end of the third power transmission line, and the tail end of the third power transmission line is suspended; the head end of the fourth transmission line is grounded, and the tail end of the fourth transmission line is suspended;

step 3, measuring the power failure of the line, and synchronously measuring to obtain zero-sequence components in different zero-sequence measurement modes by using a synchronous Phasor Measurement Unit (PMU);

step 3, the zero sequence components under different zero sequence measurement modes comprise:

zero-sequence voltage and zero-sequence current at the head end of the first power transmission line in different zero-sequence measurement modes and zero-sequence voltage and zero-sequence current at the tail end of the first power transmission line in different zero-sequence measurement modes; zero-sequence voltage and zero-sequence current at the head end of the second power transmission line in different zero-sequence measurement modes and zero-sequence voltage and zero-sequence current at the tail end of the second power transmission line in different zero-sequence measurement modes; zero-sequence voltage and zero-sequence current at the head end of the third power transmission line in different zero-sequence measurement modes and zero-sequence voltage and zero-sequence current at the tail end of the third power transmission line in different zero-sequence measurement modes; zero-sequence voltage and zero-sequence current at the head end of the fourth transmission line in different zero-sequence measurement modes, and zero-sequence voltage and zero-sequence current at the tail end of the fourth transmission line in different zero-sequence measurement modes;

the zero sequence voltage of the head end of the first power transmission line under different zero sequence measurement modes is as follows: u shape_k,1,s,k∈[1,4]Wherein, U_k,1,sRepresenting the zero sequence voltage of the head end of the first transmission line in a kth zero sequence measurement mode;

the zero sequence current of the head end of the first power transmission line under different zero sequence measurement modes is I_k,1,s,k∈[1,4]Wherein, I_k,1,sRepresenting the zero sequence current of the first transmission line head end under the k zero sequence measurement mode;

the zero sequence voltage of the head end of the second power transmission line under different zero sequence measurement modes is as follows: u shape_k,2,s,k∈[1,4]Wherein, U_k,2,sRepresenting the zero sequence voltage of the head end of the second transmission line in the kth zero sequence measurement mode;

the zero-sequence current of the head end of the second power transmission line under different zero-sequence measurement modes is I_k,2,s,k∈[1,4]Wherein, I_k,2,sRepresenting the zero sequence current of the head end of the second transmission line in the kth zero sequence measurement mode;

the zero sequence voltage of the head end of the third power transmission line under different zero sequence measurement modes is as follows: u shape_k,3,s,k∈[1,4]Wherein, U_k,3,sRepresenting the zero sequence voltage of the head end of the third transmission line in the kth zero sequence measurement mode;

the first under different zero sequence measurement modesThe zero sequence current at the head end of the three power transmission lines is I_k,3,s,k∈[1,4]Wherein, I_k,3,sRepresenting the zero sequence current of the head end of the third transmission line in the kth zero sequence measurement mode;

the zero sequence voltage of the head end of the fourth power transmission line under different zero sequence measurement modes is as follows: u shape_k,4,s,k∈[1,4]Wherein, U_k,4,sRepresenting the zero sequence voltage of the head end of the fourth transmission line in the kth zero sequence measurement mode;

the zero sequence current of the head end of the fourth power transmission line under different zero sequence measurement modes is I_k,4,s,k∈[1,4]Wherein, I_k,4,sRepresenting the zero sequence current of the head end of the fourth transmission line in the kth zero sequence measurement mode;

the zero sequence voltage at the tail end of the first power transmission line under different zero sequence measurement modes is as follows: u shape_k,1,m,k∈[1,4]Wherein, U_k,1,mRepresenting the zero sequence voltage of the tail end of the first transmission line in a kth zero sequence measurement mode;

the zero-sequence current at the tail end of the first power transmission line under different zero-sequence measurement modes is I_k,1,m,k∈[1,4]Wherein, I_k,1,mRepresenting the zero sequence current of the tail end of the first transmission line in a kth zero sequence measurement mode;

the zero-sequence voltage at the tail end of the second power transmission line under different zero-sequence measurement modes is as follows: u shape_k,2,m,k∈[1,4]Wherein, U_k,2,mRepresenting the zero sequence voltage of the tail end of the second transmission line in a k zero sequence measurement mode;

the zero-sequence current at the tail end of the second power transmission line under different zero-sequence measurement modes is I_k,2,m,k∈[1,4]Wherein, I_k,2,mRepresenting the zero sequence current at the tail end of the second transmission line in a kth zero sequence measurement mode;

the zero-sequence voltage at the tail end of the third power transmission line under different zero-sequence measurement modes is as follows: u shape_k,3,m,k∈[1,4]Wherein, U_k,3,mRepresenting the zero sequence voltage of the tail end of the third transmission line in the kth zero sequence measurement mode;

the zero-sequence current at the tail end of the third power transmission line under different zero-sequence measurement modes is I_k,3,m,k∈[1,4]Which isIn (I)_k,3,mRepresenting the zero sequence current of the end of the third transmission line in the kth zero sequence measurement mode;

the zero-sequence voltage at the tail end of the fourth power transmission line under different zero-sequence measurement modes is as follows: u shape_k,4,m,k∈[1,4]Wherein, U_k,4,mRepresenting the zero sequence voltage of the tail end of the fourth transmission line in a kth zero sequence measurement mode;

the zero-sequence current at the tail end of the fourth power transmission line under different zero-sequence measurement modes is I_k,4,m,k∈[1,4]Wherein, I_k,4,mAnd indicating the zero-sequence current at the tail end of the fourth transmission line in the kth zero-sequence measurement mode.

And 4, step 4: sequentially adopting Fourier algorithm to obtain zero sequence fundamental wave components in different zero sequence measurement modes for the zero sequence components in different zero sequence measurement modes; calculating a line transmission matrix according to all zero sequence fundamental wave components; calculating zero-sequence impedance and zero-sequence admittance of the first double-circuit characteristic root, the second double-circuit characteristic root and the first and last double-circuit coupling parts of the line according to non-zero elements of a line transmission matrix, and further calculating zero-sequence resistance, zero-sequence inductance and zero-sequence capacitance of the first and last double-circuit coupling parts of the line; calculating a first-section double-loop intermediate variable to a sixth first-section double-loop intermediate variable and a first-section double-loop intermediate variable to a sixth end-section double-loop intermediate variable according to the first double-loop characteristic root, the second double-loop characteristic root, and the zero-sequence impedance and the zero-sequence admittance of the first-section and the end-section double-loop coupling part of the line; calculating an intermediate variable from a first characteristic to an eighth characteristic intermediate variable and an intermediate variable from a first element to an eighth element according to non-zero elements of the transmission matrix, the first-segment double-loop intermediate variable to the sixth first-segment double-loop intermediate variable and the first last-segment double-loop intermediate variable to the sixth last-segment double-loop intermediate variable; calculating a first fourth-return feature root to a fourth-return feature root according to the first feature intermediate variable to the eighth feature intermediate variable; calculating a first intermediate substitution variable to a fourth intermediate substitution variable according to the first-fourth-return feature root to the fourth-return feature root, wherein the first intermediate substitution variable to the fourth intermediate substitution variable are calculated; calculating first matrix intermediate variables to eighth matrix intermediate variables according to the first intermediate replacement variables to the fourth intermediate replacement variables, the first fourth-turn feature roots to the fourth-turn feature roots and the first feature intermediate variables to the eighth feature intermediate variables; calculating a zero sequence impedance matrix of the four-loop coupling part in the middle section of the line according to the intermediate variables from the first element intermediate variable to the eighth element, the intermediate variables from the first intermediate substitution variable to the fourth intermediate substitution variable, the feature roots from the first four-loop feature roots to the fourth four-loop feature roots and the intermediate variables from the first matrix intermediate variable to the eighth matrix; calculating an admittance matrix of the four-loop coupling part at the middle section of the line according to the impedance matrix of the four-loop coupling part at the middle section of the line and the intermediate variables from the first matrix to the eighth matrix; and calculating zero sequence resistance, zero sequence inductance and zero sequence capacitance of the four-circuit coupling parts in the middle section of the circuit according to the impedance matrix and the admittance matrix of the four-circuit coupling parts in the middle section of the circuit.

And 4, sequentially adopting Fourier algorithm to obtain zero-sequence fundamental components in different zero-sequence measurement modes by the zero-sequence components in different zero-sequence measurement modes as follows: take k e [1,4], and

zero-sequence voltage of first transmission line head end under kth zero-sequence measurement mode, namely U_k，1，sObtaining zero sequence fundamental wave voltage of the head end of the first transmission line in the kth zero sequence measurement mode by adopting a Fourier algorithm

Zero-sequence current I at head end of first power transmission line in kth zero-sequence measurement mode_k，1，sObtaining zero sequence fundamental current of the head end of the first transmission line in the kth zero sequence measurement mode by adopting a Fourier algorithm

Zero-sequence voltage of the head end of the second transmission line under the kth zero-sequence measurement mode, namely U_k，2，sObtaining zero sequence fundamental wave voltage of the head end of the second transmission line in the kth zero sequence measurement mode by adopting a Fourier algorithm

Zero-sequence current I at head end of second transmission line in kth zero-sequence measurement mode_k，2，sObtaining zero sequence fundamental current of the head end of the second transmission line in the kth zero sequence measurement mode by adopting a Fourier algorithm

Zero-sequence voltage of the head end of the third transmission line, namely U, in the kth zero-sequence measurement mode_k，3，sObtaining zero sequence fundamental wave voltage of the head end of the third transmission line in the kth zero sequence measurement mode by adopting a Fourier algorithm

Zero-sequence current I at head end of third transmission line in kth zero-sequence measurement mode_k，3，sObtaining zero sequence fundamental current of the head end of the third transmission line in the kth zero sequence measurement mode by adopting a Fourier algorithm

Zero-sequence voltage of head end of fourth transmission line, namely U, in kth zero-sequence measurement mode_k，4，sObtaining zero sequence fundamental wave voltage of the head end of the fourth transmission line in the kth zero sequence measurement mode by adopting a Fourier algorithm

Zero-sequence current I at head end of fourth power transmission line in kth zero-sequence measurement mode_k，4，sObtaining zero sequence fundamental current of the head end of the fourth transmission line in the kth zero sequence measurement mode by adopting a Fourier algorithm

Zero-sequence voltage at tail end of first power transmission line, namely U, in kth zero-sequence measurement mode_k，1，mObtaining zero sequence fundamental wave voltage at the tail end of the first transmission line in the kth zero sequence measurement mode by adopting a Fourier algorithm, namely

Zero-sequence current I at tail end of first power transmission line in kth zero-sequence measurement mode_k，1，mObtaining the zero sequence fundamental current at the tail end of the first transmission line in the kth zero sequence measurement mode by adopting a Fourier algorithm, namely

Zero-sequence voltage at tail end of second power transmission line, namely U, in kth zero-sequence measurement mode_k，2，mObtaining zero sequence fundamental wave voltage at the tail end of the second transmission line in the kth zero sequence measurement mode by adopting a Fourier algorithm, namely

Zero-sequence current I at tail end of second power transmission line in kth zero-sequence measurement mode_k，2，mObtaining the zero sequence fundamental current at the tail end of the second transmission line in the kth zero sequence measurement mode by adopting a Fourier algorithm, namely

Zero-sequence voltage at the tail end of a third power transmission line, namely U, in a kth zero-sequence measurement mode_k，3，mObtaining zero sequence fundamental wave voltage at the tail end of the third transmission line in the kth zero sequence measurement mode by adopting a Fourier algorithm, namely

Zero-sequence current I at the end of the third transmission line in the kth zero-sequence measurement mode_k，3，mObtaining zero sequence fundamental current at the tail end of the third transmission line in the kth zero sequence measurement mode by adopting a Fourier algorithm, namely

Zero-sequence voltage at tail end of fourth power transmission line, namely U, in kth zero-sequence measurement mode_k，4，mObtaining zero sequence fundamental wave electricity of the tail end of the fourth transmission line in a kth zero sequence measurement mode by adopting a Fourier algorithmPressing the mixture

Zero-sequence current I at tail end of fourth power transmission line in kth zero-sequence measurement mode_k，4，mObtaining zero sequence fundamental current at the tail end of the fourth transmission line in the kth zero sequence measurement mode by adopting a Fourier algorithm, namely

Step 4, calculating the non-zero elements of the line transmission matrix according to all the zero sequence fundamental wave components is as follows:

in the formula:

obtaining a transmission matrix with complete lines:

in the formula, T_mnElements representing the row a, column b of the transmission matrix, a ∈ [1,8 ]]，b∈[1,8]；

Step 4, calculating the zero sequence impedance and zero sequence admittance of the first double-circuit characteristic root, the second double-circuit characteristic root and the double-circuit coupling part of the first section and the last section of the line according to the non-zero elements of the transmission matrix as follows:

in the formula I₁The length from the head end of the first-section double-circuit coupling part line to the tail end of the first-section double-circuit coupling part line, l₃The length from the head end of the tail section double-circuit coupling part line to the tail end of the tail section double-circuit coupling part line; r is₁Is the first double-round feature root, r₂Is a second double-loop feature root; z_sZero sequence self-impedance, Z, of double-circuit coupling parts of the first and last sections of the line_mZero-sequence mutual impedance of the double-circuit coupling parts of the first and the last sections of the line; y is_sFor zero-sequence self-admittance, Y, of double-circuit coupling parts of the first and last sections of the line_mZero sequence mutual admittance of the double-circuit coupling parts at the first and the last sections of the line;

step 4, calculating the zero sequence resistance, the zero sequence inductance and the zero sequence capacitance of the double-circuit coupling parts of the line head and the line tail according to the zero sequence impedance and the zero sequence admittance of the double-circuit coupling parts of the line head and the line tail:

in the formula, R_sZero sequence self-resistance, L, for the double-circuit coupling part of the line head and end sections_sZero sequence self-inductance C of double-circuit coupling part at first and last sections of line_sThe zero sequence self-capacitance is the zero sequence self-capacitance of the double-circuit coupling part at the first and the last sections of the line; r_mZero-sequence mutual resistance, L, of double-circuit coupling parts at first and last sections of line_mZero-sequence mutual inductance of double-circuit coupling parts at first and last sections of line, C_mThe zero-sequence mutual capacitance of the double-circuit coupling part at the first and the last sections of the line.

Step 4, calculating a first-section double-loop intermediate variable to a sixth first-section double-loop intermediate variable and a first end-section double-loop intermediate variable to a sixth end-section double-loop intermediate variable according to the first double-loop characteristic root, the second double-loop characteristic root, the zero-sequence impedance of the first and last section double-loop coupling part of the line and the zero-sequence admittance:

in the formula, m₁、n₁、s₁、q₁、h₁、k₁For the c first double-loop intermediate variable, c is equal to [1,6 ]]； m₂、n₂、s₂、q₂、h₂、k₂For the d-th end double-loop intermediate variable, d ∈ [1,6 ]]；

Step 4, calculating a first characteristic intermediate variable to an eighth characteristic intermediate variable and a first element intermediate variable to an eighth element intermediate variable according to the non-zero elements of the transmission matrix, the first-segment double-loop intermediate variable to the sixth first-segment double-loop intermediate variable and the first last-segment double-loop intermediate variable to the sixth last-segment double-loop intermediate variable:

in the formula, σ_uvRepresents the e characteristic intermediate variable, e ∈ [1,8 ]]；Represents the intermediate variable of the f element, f is equal to [1,8 ]]；u∈[1,2]，v∈[1,4]；

Step 4, calculating a first fourth-round feature root, a second fourth-round feature root, a third fourth-round feature root and a fourth-round feature root according to the first to eighth feature intermediate variables:

in the formula I₂The length from the head end of the middle section four-loop coupling part line to the tail end of the middle section four-loop coupling part line; p is a radical of₁Is the first four-pass feature root, p₂Is the second four-pass feature root, p₃Is a third four-round feature root, p₄Is the fourth-round feature root;

step 4, calculating a first intermediate substitution variable to a fourth intermediate substitution variable according to the first fourth-turn feature root to the fourth-turn feature root, wherein the first intermediate substitution variable to the fourth intermediate substitution variable are as follows:

in the formula, alpha_gFor the g-th intermediate replacement variable, g ∈ [1,4]]；β_hIs the h-th intermediate substitution variable, h ∈ [1,4]]；

Step 4, calculating intermediate variables from the first matrix intermediate variable to the eighth matrix according to the intermediate variables from the first intermediate replacement variable to the fourth intermediate replacement variable, the feature root of the first fourth turn to the feature root of the fourth turn, and the intermediate variables from the first feature intermediate variable to the eighth feature intermediate variable:

in the formula, K_xyRepresents the ith characteristic intermediate variable, i ∈ [1,8 ]]；x∈[1,2]，y∈[1,4]；

Step 4, calculating a zero sequence impedance matrix of the four-loop coupling part in the middle section of the line according to the intermediate variables from the first element intermediate variable to the eighth element intermediate variable, the intermediate substituted variables from the first intermediate substituted variable to the fourth intermediate substituted variable, the feature roots from the first fourth loop to the fourth loop, and the intermediate variables from the first matrix intermediate variable to the eighth matrix, wherein the zero sequence impedance matrix is as follows:

in the formula: z_aZero sequence self-impedance of four-loop coupling parts in the middle sections of the first transmission line and the second transmission line; z_cZero sequence self-impedance of four loop coupling parts in the middle sections of a third power transmission line and a fourth power transmission line; z_abZero-sequence mutual impedance of four-loop coupling parts in the middle sections of the first power transmission line and the second power transmission line; z_acThe zero-sequence mutual impedance of the four-loop coupling parts at the middle sections of the first transmission line and the third transmission line is obtained, and the zero-sequence mutual impedance of the four-loop coupling parts at the middle sections of the second transmission line and the fourth transmission line is also obtained; z_adZero-sequence mutual impedance of four-circuit coupling parts at the middle sections of the first transmission line and the fourth transmission line is provided, and zero-sequence mutual impedance of four-circuit coupling parts at the middle sections of the second transmission line and the third transmission line is also provided; z_cdZero sequence mutual impedance of four-loop coupling parts at the middle sections of the third power transmission line and the fourth power transmission line is obtained;

step 4, calculating the admittance matrix of the four-loop coupling part at the middle section of the line according to the impedance matrix of the four-loop coupling part at the middle section of the line and the intermediate variable from the first matrix to the eighth matrix, wherein the admittance matrix is as follows:

in the formula:

in the formula: y is_aZero sequence self-admittance of four-circuit coupling parts at the middle sections of the first transmission line and the second transmission line; y is_cZero sequence self-admittance of four-circuit coupling parts at the middle sections of a third power transmission line and a fourth power transmission line; y is_abZero sequence mutual admittance of four-circuit coupling parts at the middle sections of the first transmission line and the second transmission line; y is_acZero sequence mutual admittance of the four-loop coupling parts at the middle sections of the first transmission line and the third transmission line, and zero sequence mutual admittance of the four-loop coupling parts at the middle sections of the second transmission line and the fourth transmission line; y is_adZero-sequence mutual admittance of the four-loop coupling parts at the middle sections of the first transmission line and the fourth transmission line, and zero-sequence mutual admittance of the four-loop coupling parts at the middle sections of the second transmission line and the third transmission line; y is_cdZero sequence mutual admittance of four-loop coupling parts at the middle sections of a third power transmission line and a fourth power transmission line;

step 4, calculating zero sequence resistance, zero sequence inductance and zero sequence capacitance of the four-circuit coupling part in the middle section of the line according to the impedance matrix and the admittance matrix of the four-circuit coupling part in the middle section of the line as follows:

in the formula: r_aFor four-circuit coupling part in middle section of first transmission lineA zero sequence self-resistance; r_bThe zero sequence self-resistance is the zero sequence self-resistance of the four-circuit coupling part at the middle section of the second power transmission line; r_cThe zero sequence self-resistance of the four-circuit coupling part at the middle section of the third power transmission line; r_dThe zero sequence self-resistance of the four-circuit coupling part at the middle section of the fourth power transmission line; r_abZero-sequence mutual resistance of four-circuit coupling parts at the middle sections of the first power transmission line and the second power transmission line; r_acIs zero sequence mutual resistance, R, of four-circuit coupling parts at the middle sections of the first transmission line and the third transmission line_bdZero-sequence mutual resistance of four-circuit coupling parts at the middle sections of the second power transmission line and the fourth power transmission line; r_adIs zero sequence mutual resistance, R, of four-circuit coupling parts at middle sections of a first power transmission line and a fourth power transmission line_bcZero-sequence mutual resistance of four-circuit coupling parts at the middle sections of the second power transmission line and the third power transmission line; r_cdZero-sequence mutual resistance of four-circuit coupling parts at the middle sections of the third power transmission line and the fourth power transmission line;

L_athe zero sequence self-inductance is a zero sequence self-inductance of a four-circuit coupling part at the middle section of the first power transmission line; l is_bThe zero sequence self-inductance is the zero sequence self-inductance of the four-circuit coupling part in the middle section of the second power transmission line; l is_cThe zero sequence self-inductance is the zero sequence self-inductance of the four-turn coupling part at the middle section of the third power transmission line; l is_dThe zero sequence self-inductance is the zero sequence self-inductance of the four-circuit coupling part at the middle section of the fourth power transmission line; l is_abZero sequence mutual inductance of four-circuit coupling parts at the middle sections of the first power transmission line and the second power transmission line is obtained; l is_acZero sequence mutual inductance L of four-circuit coupling parts at middle sections of the first transmission line and the third transmission line_bdZero sequence mutual inductance of four-circuit coupling parts at the middle sections of the second power transmission line and the fourth power transmission line is obtained; l is_adIs zero sequence mutual inductance of four-circuit coupling parts at the middle sections of the first transmission line and the fourth transmission line, L_bcZero sequence mutual inductance of four-circuit coupling parts at the middle sections of the second power transmission line and the third power transmission line is obtained; l is_cdZero sequence mutual inductance of four-circuit coupling parts at the middle sections of the third power transmission line and the fourth power transmission line is obtained;

C_athe zero sequence self-capacitance is a zero sequence self-capacitance of the four-circuit coupling part at the middle section of the first power transmission line; c_bThe zero sequence self-capacitance is a zero sequence self-capacitance of the four-circuit coupling part at the middle section of the second power transmission line; c_cThe zero sequence self-capacitance is a zero sequence self-capacitance of the four-circuit coupling part at the middle section of the third power transmission line; c_dThe zero sequence self-capacitance is a zero sequence self-capacitance of the four-circuit coupling part at the middle section of the fourth power transmission line; c_abZero sequence mutual capacitance of four-circuit coupling parts at the middle sections of the first transmission line and the second transmission line; c_acZero sequence mutual capacitance C of four-circuit coupling parts at middle sections of the first transmission line and the third transmission line_bdZero-sequence mutual capacitance of four-circuit coupling parts at the middle sections of the second power transmission line and the fourth power transmission line; c_adZero sequence mutual capacitance C of four-circuit coupling parts at middle sections of the first transmission line and the fourth transmission line_bcZero-sequence mutual capacitance of four-circuit coupling parts at the middle sections of the second power transmission line and the third power transmission line; c_cdAnd the zero sequence mutual capacitance of the four-circuit coupling parts at the middle sections of the third transmission line and the fourth transmission line is obtained.

A simulation model was built in PSCAD, as shown in figure 2, from the physical model of a "three-segment" non-full-line parallel four-circuit transmission line shown in figure 1. Theoretical values of the transmission line unit length are shown in tables 1 and 2.

TABLE 1 theoretical zero-sequence parameter values of four-circuit line sections

TABLE 2 theoretical zero-sequence parameters of double-circuit line sections

The length l of the first and the last sections of the whole line of the double-loop coupling part is set in an emulation way₁、l₃Fixed, middle section four-turn coupling part length l₂The results of measurements performed by the method of the present invention, ranging from 400km to 700km, are shown in tables 3, 4 and 5.

TABLE 3 zero sequence resistance measurement results of the method of the invention

Table 4 zero sequence inductance measurement of the method of the present invention

TABLE 5 zero sequence capacitance measurement results of the method of the present invention

The conventional measurement method is a single-ended measurement method. The method is based on a centralized parameter model, and considers that the parameters of all lines are always the same no matter how the transmission lines are coupled around, namely, the default Z of the three-section type non-full-line parallel mixed-voltage four-line circuit is_S＝Z_a,Z_m＝Z_ab,Y_S＝Y_a,Y_m＝Y_ab. Because the traditional measurement method can only measure one parameter at a time, the traditional method needs 12 measurement modes in total for measuring all zero sequence parameters. The measurement results obtained by the conventional measurement method under the same simulation setting are shown in table 6.

TABLE 6 simulation measurements of the conventional method

As shown in FIG. 3, the length l of the four-loop coupling part in the middle section of the line is compared with the conventional method₂Comparing the measurement errors at the time of 300-,And the maximum value of the relative error of the zero sequence inductance and the zero sequence capacitance is measured.

Adjusting the simulation setting to make the length l of the four-circuit coupling part in the middle section of the whole line₂Fixed, first and last segment double-back coupling part length l₁+l₃From 100km to 450km, measurement errors obtained by measurement by using the method of the embodiment and the conventional method are shown in fig. 4, wherein R, L, C is the maximum value of the relative error of the measurement of the zero-sequence resistance, the zero-sequence inductance and the zero-sequence capacitance of the double-circuit coupling part at the head and the tail of the line respectively.

The following conclusions can be drawn from the analysis of tables 3-6 and fig. 3 and 4:

1) in the traditional method, because the long-line distribution effect is not considered, a centralized parameter model is adopted for modeling and measuring, so that the error of each measured zero-sequence parameter is larger along with the increase of the line length, and if the measurement error of the zero-sequence resistance is larger than 100 percent along with the increase of the line length, the measurement precision required by engineering cannot be met; in addition, the traditional method does not consider different electromagnetic coupling relations when different circuits are parallel, considers that circuit parameters are the same in all lines, which is not in accordance with the actual situation, and is not suitable for non-all-line parallel mixed-voltage multi-circuit power transmission lines.

2) In the method, the long-line distribution effect is considered, a distribution parameter model is adopted for modeling, and zero sequence distribution parameters of the middle-section four-circuit coupling part and the first-and-last-section double-circuit coupling part of the circuit are respectively measured aiming at the condition that the zero sequence parameters of each section of the circuit are different due to different electromagnetic coupling conditions of each section of the circuit of a non-full-line parallel mixed-compression four-circuit. The measurement result shows that the change of the line length hardly influences the measurement precision of the method. For the four-circuit coupling part in the middle section of the line, the measurement error of the zero-sequence resistance is not more than 1.1 percent, the measurement error of the zero-sequence inductance is not more than 0.4 percent, and the measurement error of the zero-sequence capacitance is not more than 0.8 percent; for the double-circuit coupling part of the line head and tail sections, the measurement error of the zero-sequence resistance is not more than 0.9%, the measurement error of the zero-sequence inductance is not more than 0.5%, and the measurement error of the zero-sequence capacitance is not more than 0.9%.

In the description of the present invention, it should be noted that the terms "upper", "lower", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and operate, and thus, should not be construed as limiting the present invention. Unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are intended to be inclusive and mean, for example, that they may be fixedly, removably, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those of ordinary skill in the art according to specific situations.

It is to be noted that, in the present invention, relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The foregoing is merely exemplary of the invention, which can be understood and carried into effect by those skilled in the art. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.