阅读说明：本技术 一种基于Bergeron线路模型的特高压直流输电线路区内外故障识别方法 (Extra-high voltage direct current transmission line area internal and external fault identification method based on Bergeron line model ) 是由 束洪春 龙立阿 田鑫萃 王璇 袁小兵 于 2019-07-19 设计创作，主要内容包括：本发明涉及一种基于Bergeron线路模型的特高压直流输电线路区内外故障识别方法,属于输电线路继电保护技术领域。首先读取位于输电线路M端和N端的高速采集装置测得的电压和电流数据；其次基于Bergeron线路模型由M端电压、电流推算出N端电流；用推算出的N端电流和实测的N端电流在故障后半线长时窗内,求电流积分值的差值,若其差值小于或等于设定的阈值则为区外故障,若其差值大于阈值,则初判为区内故障；再用计算得到的线路中点处以及线长3/4处的数值,进一步确定是否为区内故障。本发明避免了分布电容电流带来的不良影响,适用于特高压直流输电线路。仿真验证结果表明,该方法正确有效。(The invention relates to an ultra-high voltage direct current transmission line area internal and external fault identification method based on a Bergeron line model, and belongs to the technical field of relay protection of transmission lines. Firstly, reading voltage and current data measured by high-speed acquisition devices positioned at the M end and the N end of a power transmission line; secondly, calculating N-terminal current from M-terminal voltage and current based on a Bergeron line model; calculating the difference value of current integral values by using the calculated N-terminal current and the actually measured N-terminal current in a half-linear time window after the fault, if the difference value is less than or equal to a set threshold value, determining the current integral value as an out-of-area fault, and if the difference value is greater than the threshold value, initially determining the current integral value as an in-area fault; and further determining whether the fault is an intra-area fault or not by using the calculated values at the midpoint of the line and the 3/4 of the line length. The invention avoids the adverse effect caused by the distributed capacitance current and is suitable for the ultra-high voltage direct current transmission line. The simulation verification result shows that the method is correct and effective.)

1. a method for identifying faults inside and outside an extra-high voltage direct current transmission line area based on a Bergeron line model is characterized by comprising the following steps: firstly, reading voltage and current data measured by high-speed acquisition devices positioned at the M end and the N end of a power transmission line; secondly, calculating N-terminal current from M-terminal voltage and current based on a Bergeron line model; calculating the difference value of current integral values by using the calculated N-terminal current and the actually measured N-terminal current in a half-line long window after the fault, if the difference value is less than or equal to a set threshold value, determining the current integral value as an out-of-area fault, and if the difference value is greater than the threshold value, initially determining the current integral value as an in-area fault; and further judging whether the fault is an in-zone fault or not by using the calculated values at the line midpoint and the line length of 3/4.

2. The method for identifying the faults inside and outside the ultrahigh voltage direct current transmission line based on the Bergeron line model according to claim 1 is characterized by comprising the following specific steps of:

step 1: reading current and voltage traveling wave data of an M end and an N end of the direct current transmission line in fault;

Step 2: based on a Bergeron line model, calculating the current of the N end according to the data obtained by the M end in the formula (1);

The current distribution along the line can be calculated by M-end data and N-end data respectively through formulas (1) and (2), wherein: i is_Mf,s(x, t) and I_Nf,s(x, t) represents the current value at t moment at x position from M end calculated by M end data and N end data, x represents the distance from M end, t represents any moment, Z_c,sRepresenting the wave impedance, r, of the transmission line_sRepresenting the line resistance per unit length, v_sRepresenting the wave speed of the traveling wave, and l representing the total length of the transmission line;

andto representVoltage and current detected at the end M at the moment;

u_M,s(t) and i_M,s(t) respectively representing the voltage and the current detected by the M terminal at the t moment;

andTo representvoltage and current detected at the end M at the moment;

AndTo representVoltage and current detected at the N end at the moment;

u_N,s(t) and i_N,s(t) respectively representing the voltage and the current detected by the N end at the time t;

AndTo representvoltage and current detected at the N end at the moment;

Step 3: integrating and subtracting the N-terminal current calculated in Step2 and the actual current detected by the N terminal within a half time window after the fault is selected, and judging as an out-of-area fault if the difference is smaller than a setting value; if the difference value is larger than or equal to the setting value, primarily judging to be an intra-area fault, and turning to the fourth step for further judgment, wherein the criterion is as follows:

if it isAn out-of-range fault is detected; (3)

if it isthe fault is judged as an internal fault for the first time; (4)

step 4: based on a Bergeron line model, calculating the current at the midpoint of the line by using the data obtained by the M end and the current at the midpoint of the line by using the data obtained by the N end, integrating and subtracting the current in a half-length time window after the fault, and judging the fault in the area if the difference is smaller than a setting value; if the difference value is greater than or equal to the setting value, the fault is judged to be a long-distance high-resistance fault, the fifth step is carried out for further judgment, the current at the midpoint of the fault moment is calculated by the formulas (1) and (2), and the criterion is as follows:

If it isDetermining the fault is an intra-area fault; (5)

If it isFurther determination is needed; (6)

Step 5: based on a Bergeron line model, calculating the current at the position of 3/4 of the line length by the data obtained by the M end and the current at the position of 1/4 of the line length by the data obtained by the N end in the half-time window after the fault, integrating and subtracting, and judging as an in-region fault if the difference value is smaller than a setting value; if the difference value is larger than or equal to the setting value, the judgment is invalid, the currents at the positions 3/4 away from the M end at the fault moment are calculated by the formulas (1) and (2), and the criterion is as follows:

If it isdetermining the fault is an intra-area fault; (7)

If it isJudging to be invalid; (8)

In the above formulae (3) to (8), t₀At the time of occurrence of the fault, Δ t is a time integration window, I_M,l,s(t) is the N-terminal current deduced from M, I_N(t) is the current detected at the N terminal,. DELTA.I_1setto a setting value, Δ I_1set＝2；I_M,l/2,s(t) is the current at the midpoint of the line, I, as deduced from M_N,l/2,s(t) current at midpoint of line, Δ I, deduced for N_2setTo a setting value, Δ I_2set＝0.4，I_M,3l/4,s(t) is the current at line length 3/4, deduced from M, I_N,l/4,s(t) the current at 1/4 of the line length, Δ I, deduced for N_3setTo a setting value, Δ I_3set＝10。

Technical Field

The invention relates to an ultra-high voltage direct current transmission line area internal and external fault identification method based on a Bergeron line model, and belongs to the technical field of relay protection of transmission lines.

Background

The distribution of electric energy and load centers in China is extremely uneven, and the phenomenon that energy resources are mainly concentrated in western regions is shown, and most of the electric load centers are located in eastern economically developed regions. Compared with alternating current transmission, direct current transmission is not restricted by the problem of synchronous operation stability, stable operation of alternating current power grids at two ends can be guaranteed, the method is suitable for long-distance high-power transmission, and the method can be connected with two systems with different frequencies to realize asynchronous networking. Protection and fault location of a direct current transmission line are important components of a direct current transmission project.

according to the fact that the proportion of the faults of the transmission line in the direct-current transmission system exceeds 50%, the faults of the direct-current transmission line directly threaten the safety of the direct-current transmission system and simultaneously affect the reliable operation of an alternating-current power grid connected with the direct-current transmission line. The quick response, reliable and sensitive direct current line protection is an important guarantee for the safe operation of the ultra-high voltage direct current transmission and even the power system. The invention provides a Bergeron line model-based method for identifying faults inside and outside an ultra-high voltage direct current transmission line area, which provides a basis for rapid and selective actions of transmission line protection.

Disclosure of Invention

The invention aims to solve the technical problem of providing a method for identifying faults inside and outside an extra-high voltage direct current transmission line area based on a Bergeron line model, which is used for solving the problems.

The technical scheme of the invention is as follows: a method for identifying faults inside and outside an extra-high voltage direct current transmission line area based on a Bergeron line model comprises the steps of firstly, reading voltage and current data measured by high-speed acquisition devices positioned at an M end and an N end of the transmission line; secondly, calculating N-terminal current from M-terminal voltage and current based on a Bergeron line model; calculating the difference value of current integral values by using the calculated N-terminal current and the actually measured N-terminal current in a fault initial instant short time window, and if the difference value is less than or equal to a set threshold value, determining that the fault is an out-of-area fault, and if the difference value is greater than the threshold value, determining that the fault is an in-area fault; and further determining whether the fault is an intra-area fault or not by using the calculated values at the midpoint of the line and the 3/4 of the line length.

The method comprises the following specific steps:

step 1: reading current and voltage traveling wave data of an M end and an N end of the direct current transmission line in fault;

step 2: based on a Bergeron line model, calculating the current of the N end according to the data obtained by the M end in the formula (1);

the current distribution along the line can be calculated by M-end data and N-end data respectively through formulas (1) and (2), wherein: i is_{M f,s}(x, t) and I_{N f,s}(x, t) represents the current value at t moment at x position from M end calculated by M end data and N end data, x represents the distance from M end, t represents any moment, Z_c,srepresenting the wave impedance, r, of the transmission line_srepresenting the line resistance per unit length, v_sRepresenting the wave speed of the traveling wave, and l representing the total length of the transmission line;

AndTo representvoltage and current detected at the end M at the moment;

u_M,s(t) and i_M,s(t) respectively representing the voltage and the current detected by the M terminal at the t moment;

Andto representVoltage and current detected at the end M at the moment;

Andto representVoltage and current detected at the N end at the moment;

u_N,s(t) and i_N,s(t) respectively representing the voltage and the current detected by the N end at the time t;

andTo representVoltage and current detected at the N end at the moment;

step 3: integrating and subtracting the N-terminal current calculated in Step2 and the actual current detected by the N terminal within a half time window after the fault is selected, and judging as an out-of-area fault if the difference is smaller than a setting value; if the difference value is larger than or equal to the setting value, primarily judging to be an intra-area fault, and turning to the fourth step for further judgment, wherein the criterion is as follows:

If it isAn out-of-range fault is detected; (3)

If it isThe fault is judged as an internal fault for the first time; (4)

Step 4: based on a Bergeron line model, calculating the current at the midpoint of the line by using the data obtained by the M end and the current at the midpoint of the line by using the data obtained by the N end, integrating and subtracting the current in a half-length time window after the fault, and judging the fault in the area if the difference is smaller than a setting value; if the difference value is greater than or equal to the setting value, the fault is judged to be a long-distance high-resistance fault, the fifth step is carried out for further judgment, the current at the midpoint of the fault moment is calculated by the formulas (1) and (2), and the criterion is as follows:

If it isDetermining the fault is an intra-area fault; (5)

If it isFurther determination is needed; (6)

Step 5: based on a Bergeron line model, calculating the current at the position of 3/4 of the line length by the data obtained by the M end and the current at the position of 1/4 of the line length by the data obtained by the N end in the half-time window after the fault, integrating and subtracting, and judging as an in-region fault if the difference value is smaller than a setting value; if the difference value is larger than or equal to the setting value, the judgment is invalid, the currents at the positions 3/4 away from the M end at the fault moment are calculated by the formulas (1) and (2), and the criterion is as follows:

If it isdetermining the fault is an intra-area fault; (7)

if it isJudging to be invalid; (8)

in the above formulae (3) to (8), t₀At the time of occurrence of the fault, Δ t is a time integration window, I_M,l,s(t) is the N-terminal current deduced from M, I_N(t) is the current detected at the N terminal,. DELTA.I_1setTo a setting value, Δ I_1set＝2；I_M,l/2,s(t) is the current at the midpoint of the line, I, as deduced from M_N,l/2,s(t) current at midpoint of line, Δ I, deduced for N_2setTo a setting value, Δ I_2set＝0.4， I_M,3l/4,s(t) is the current at line length 3/4, deduced from M, I_N,l/4,s(t) the current at 1/4 of the line length, Δ I, deduced for N_3setTo a setting value, Δ I_3set＝10。

the invention has the beneficial effects that:

(1) The method for judging the faults inside and outside the area is based on a Bergeron power transmission line model along-line current distribution calculation formula and a kirchhoff current law, and the principle is simple.

(2) The current of the reference point is calculated to two sides of the reference point, and adverse effects caused by distributed current are avoided.

(3) The N end, l/2 position and 3l/4 position of the line are selected as reference points, integral difference values of Bergeron currents at two ends of the 3 reference points and a transverse axis are respectively calculated, the fault is judged to be located inside or outside the line, and the problem that the calculated value is influenced by the unique reference point is solved through the selection of the reference points.

drawings

FIG. 1 is a diagram of a simulation model of an extra-high voltage DC power transmission system according to the present invention;

FIG. 2 is a graph of the estimated current value from the M terminal to the N terminal and the measured current value from the N terminal under the condition of f1 fault according to the present invention;

FIG. 3 is a diagram of the estimated current values when the M terminal and the N terminal are estimated to the midpoint of the line under the f1 fault condition;

FIG. 4 is a graph of the estimated current value from the M terminal to the N terminal and the measured current value from the N terminal under the condition of f2 fault according to the present invention;

FIG. 5 is a diagram of the estimated current values when the M terminal and the N terminal are estimated to the midpoint of the line under the f2 fault condition according to the present invention;

FIG. 6 is a graph of the estimated current values when the M terminal is estimated to 3l/4 and the N terminal is estimated to 3l/4 under the condition of f2 fault according to the present invention;

FIG. 7 is a graph of the estimated current value from the M terminal to the N terminal and the measured current value from the N terminal under the condition of f3 fault according to the present invention;

FIG. 8 is a graph of the integrated difference when the M terminal and the N terminal estimate to the midpoint of the line under the f3 fault condition of the present invention;

FIG. 9 is a graph of the estimated current value from the M terminal to the N terminal and the measured current value from the N terminal under the condition of the f4 fault according to the present invention;

fig. 10 is a diagram showing estimated current values when M terminal and N terminal are estimated to the midpoint of the line in the case of a failure of f4 according to the present invention.

Detailed Description

The invention is further described with reference to the following drawings and detailed description.

The invention uses PSCAD/EMTDC simulation software to perform simulation verification on a high-voltage direct-current power transmission line model, the simulation model is a true bipolar two-end LCC direct-current power transmission system, the line length from an M end to an N end is 3300km, the voltage grade is +/-1100 kV, the simulation model topology is shown in figure 1, the sampling frequency in simulation is 50kHz, and the time (xl/2 v/2 v) required by half line length is propagated by traveling waves_s) As a time window, 5.56ms after the failure is taken as a data processing time window, and the failure occurs at 0.8 s. Wave impedance Z of power transmission line_c,s390.1416 omega, resistance r_s0.04633 Ω/km, wave velocity v_s＝2.9657×10⁵km/s。