阅读说明：本技术 一种在气体绝缘变电站中测量tev和tgpr的方法 (Method for measuring TEV and TGPR in gas insulated substation ) 是由 申巍 王森 杨帆 吴涛 周灵亮 张璐 李伟 李新民 李志忠 于 2020-12-29 设计创作，主要内容包括：本发明请求保护一种在气体绝缘变电站中测量TEV和TGPR的方法。该方法利用屏蔽线将被测点电位引入到继电保护小室内的高压探头上,并采用信号自动采集卡对高压探头上的电压数据进行采集,利用传输线的数学模型对所采集的电压数据进行修正,最终得到精确的测量电压数据。本发明将电位参考点选在继电保护小室内接地引出线处(电位接近于零),相比通常的TEV测量方法,本发明不仅所用设备简单,而且测量结果更精确。本发明对TEV和TGPR数据进行精确测量,有利于分析GIS变电站二次设备的电磁干扰问题,对于现场及科研人员测量并掌握TEV和TGPR特性具有很大参考价值。(The invention claims a method for measuring TEV and TGPR in a gas insulated substation. The method comprises the steps of introducing the potential of a measured point to a high-voltage probe in a relay protection chamber by using a shielding wire, collecting voltage data on the high-voltage probe by using an automatic signal collection card, correcting the collected voltage data by using a mathematical model of a transmission line, and finally obtaining accurate measured voltage data. The potential reference point is selected at the grounding outgoing line in the relay protection chamber (the potential is close to zero), and compared with the common TEV measuring method, the method has the advantages that the used equipment is simple, and the measuring result is more accurate. The invention accurately measures TEV and TGPR data, is beneficial to analyzing the electromagnetic interference problem of secondary equipment of a GIS transformer substation, and has great reference value for field and scientific research personnel to measure and master TEV and TGPR characteristics.)

1. A method of measuring TEV and TGPR in a gas insulated substation, comprising the steps of:

1) and selecting the type of a high-voltage probe and the type of an automatic signal acquisition card, wherein the high-voltage probe is used for acquiring the voltage of a measuring point. The high-voltage probe is subjected to model selection according to the amplitude absolute value and the main frequency of the TEV, the tolerance voltage value and the bandwidth of the selected high-voltage probe are respectively larger than the amplitude absolute value and the main frequency of the TEV, the automatic signal acquisition card is used for acquiring voltage data on the high-voltage probe, the automatic signal acquisition card is subjected to model selection according to the number of the measuring points and the TEV main frequency, the number of acquisition channels and the bandwidth of the selected automatic signal acquisition card are respectively larger than the number of the measuring points and the TEV main frequency, and the sampling frequency of the selected automatic signal acquisition card is larger than 8 times of the TEV main frequency. Placing the selected high-voltage probe and the signal automatic acquisition card in a relay protection chamber to reduce electromagnetic disturbance;

2) and selecting a proper voltage measuring point and a proper zero potential reference point, wherein the zero potential reference point is selected at a grounding outgoing line in the relay protection chamber.

3) The potential of a measuring point is led to one end of a high-voltage probe in a relay protection chamber for input by using a shielding wire, the potential of an internal connecting point of the relay protection chamber is led to the other end of the high-voltage probe for input by using a grounding wire, and then an output signal of the high-voltage probe is connected to an automatic signal acquisition card. 4) Acquiring acquired voltage data from a signal automatic acquisition card, carrying out differential dispersion on a time domain of a telegraph equation according to a transmission line telegraph equation mathematical model, establishing a first-order differential equation set of a space, then calculating by adopting a fine integration method to obtain transmission line transient response, correcting high-frequency loss generated on a transmission line by the measured voltage by using a transmission line transient response formula, and finally obtaining an accurate measured voltage value.

2. The method for measuring TEV and TGPR in a gas insulated substation according to claim 1, wherein said step 2) selects suitable voltage measuring points and zero potential reference points, and the selection of suitable measuring points satisfies the following basic conditions: firstly, voltage response can be obtained for the operation of a circuit breaker or a disconnecting switch on a branch where a measuring point is located; the maximum voltage value can be measured, and the potential rise of the GIS shell and the transient ground potential rise can be measured; the measurement path comprises a disturbance voltage transmission path of a GIS shell, a voltage transformer and a control cubicle; and fourthly, reducing the distance between the voltage measuring point and the zero potential reference point.

3. Method for measuring TEV and TGPR in a gas-insulated substation according to claim 2, characterized in that said step 3) comprises in particular the following: when measuring a potential difference TEV (potential energy transfer) of a GIS shell relative to a grounding point of a relay protection cell, the potential of the GIS shell is led to one end of a high-voltage probe in the relay protection cell for input by using a shielding wire, the potential of the grounding point in the relay protection cell is led to the other end of the high-voltage probe in the relay protection cell for input by using a grounding wire, and then an output signal of the high-voltage probe is connected to an automatic signal acquisition card; when the transient state ground potential rise value TGPR at a certain position is measured, the potential at the grounding downlead at the position is led to one end of the high-voltage probe in the relay protection chamber for input by using the shielding wire, the potential at the grounding point in the relay protection chamber is led to the other end of the high-voltage probe for input by using the grounding wire, and then the output signal of the high-voltage probe is accessed into the acquisition card. The shielded wire used in the measurement needs to be elevated by an insulating rod on a path leading to the relay protection chamber, and is shielded.

4. The method of claim 3, wherein the TEV and TGPR are measured in the GIS switch operating in step 4), because the TEV and TGPR frequencies generated during GIS switch operation are high, skin effect is generated on the shielded wire, which causes the amplitude and phase of the signal to be related to the length and diameter of the wire, i.e. transmission line effect, when the shielded wire is equivalent to the transmission line, and for analysis, partial differential hyperbolic equation-telegraph equation is adopted as a mathematical model for describing the relation between the transmission line voltage and the current, i.e.:

wherein R, L, C and G are respectively the resistance, inductance, capacitance and conductance of the transmission line in unit length, u (x, t) and i (x, t) are respectively the voltage and current on the transmission line;

the equations (1) and (2) are discretized in the time domain:

where Δ t is t/M, t is the width of the time interval under study, and M is the number of discrete points; u. of_k＝u(x,kΔt)；i_kI (x, k Δ t), x representing the spatial coordinates, k being 0,1,2 … M;

writing equations (3), (4) as a matrix form:

X＝(u₁,...,u_M,i₁,...,i_M)^T

h, F and X are introduced mainly to convert a first-order differential equation system obtained by differential dispersion of a telegraph equation in a time domain into a matrix form, wherein X represents a column vector consisting of voltage and current variables at M time discrete points at a spatial position X on a transmission line. u. of_MRepresenting the voltage, u, at spatial position x on the transmission line at time M Δ t₀Representing the voltage, i, at a spatial position x on the transmission line at time zero₀Representing the current at spatial position x on the transmission line at time zero;

the solution of equation (5) is:

epsilon represents an integral variable X (0) and represents a column vector consisting of voltage and current variables at each time discrete point moment at the zero position of a space coordinate on a transmission line;

let the space step be Δ x, then:

where exp (H.DELTA.x) is calculated as follows:

additive theorem using exponential function

exp(H·Δx)＝[exp(H·Δx/m)]^m (8)

Generally, m is 2^NN is 20, so taylor is performed for a time segment of β Δ x/mIs unfolded with

exp(H·β)≈1+H·β+(H·β)²/2+(H·β)³/3！+(H·β)⁴/4！＝1+T_a (9)

In the formula

T_a＝H·β+(H·β)²/2+(H·β)³/3！+(H·β)⁴/4！ (10)

Decomposition of formula (8)

This decomposition proceeds n times, again because of (1+ T)_a)×(1+T_a)＝1+2T_a+T_a×T_a (12)

Therefore, the expression (11) corresponds to the following expression

for(iter＝0；iter<N；iter++)

T_a＝2T_a+T_a×T_a (13)

When the circulation is over

T＝1+T_a (14)

(10) The formulas (13), (14) are the fine calculation formulas of exp (H delta x), and it can be seen that the recursion calculation is carried out according to the formula (13), and 1 is excluded from participating in the addition operation;

according to the formula (7), as long as the voltage and the current of a certain point on the transmission line in a certain time period are known, the voltage and the current of any point on the transmission line in the time period can be obtained, the calculation adopts a recursion mode, the collected voltage data is obtained from the signal automatic acquisition card, the measured voltage data is corrected according to the formula (7), and finally, an accurate measured voltage value is obtained.

Technical Field

The invention belongs to the field of research of high-voltage measurement technology, and relates to a method for simply and accurately measuring TEV and TGPR in a GIS (geographic information System) transformer substation.

Background

Gas Insulated substations (Gas Insulated Substation) are increasingly widely used in nearly two or thirty years due to the advantages of small environmental influence factors, small occupied space, high operational reliability, few maintenance and the like. Along with the improvement of operating voltage and GIS internal gas pressure, the rapid transient process caused by the operation of the disconnecting switch, the grounding switch and the breaker is more obvious and serious, and can cause a plurality of adverse effects on the system, especially when the disconnecting switch is switched on a no-load bus, the overvoltage phenomenon and the electromagnetic compatibility problem are inevitable due to the fact that the operation probability and the frequency ratio of the disconnecting switch are larger and the operation period is longer, and the attention of the world people is more and more aroused.

When a Gas Insulated Switchgear (GIS) is used for switching on and off, steep-wave-front transient electromagnetic waves are generated between a moving contact and a static contact due to gap breakdown discharge and arc reignition, and electromagnetic leakage occurs at a sleeve, a GIS shell connecting flange and the like. The leaked Transient electromagnetic waves propagate along the GIS shell and the ground, so that the potential of the GIS shell is raised to form a potential difference between the GIS shell and the ground with zero potential, the potential difference is called as Transient Enclosure Voltage (TEV) of GIS equipment, high-frequency current with the frequency of tens of megahertz is generated and flows into the grounding grid through the grounding wire, and the grounding grid after the high-frequency current flows into the ground presents obvious high-impedance characteristic, so that the Transient Ground Potential Rise (TGPR) phenomenon of the grounding grid is caused. The results of the existing measurement studies on TEV show that TEV has the following characteristics:

(1) the absolute value of the amplitude is less than 35 kV;

(2) the duration of the single pulse is within 400 ms;

(3) the dominant frequency does not exceed 60 MHz;

with the improvement of the voltage grade of the GIS transformer substation, the general presentation is as follows: the amplitude of the electromagnetic disturbance pulse is larger, the duration of a disturbance pulse group is longer, the number of pulses is more, and in an extra-high voltage GIS device, TEV and TGPR have the characteristics of steep wave front (the rising time is as low as a few nanoseconds), high amplitude (as high as tens of kilovolts), wide frequency band (as wide as tens of megahertz) and the like, so that the safety of the GIS device and operators is seriously endangered. Therefore, the GIS substation accurately measures TEV and TGPR and masters the characteristics of the TEV and TGPR, and the method has important significance for guaranteeing the safety of operation maintenance personnel and secondary equipment of the GIS substation.

Currently, no common measurement methods and standards have been developed for TEV and TGPR measurements. At present, only the electric field probe and the resistive impedance voltage measuring device recommended by the national standard measure TEV, and for the problem, relevant scholars at home and abroad carry out deep research on the problem, and 2 types of mature measuring methods are formed: (1) using an electric field probe; (2) with the use of an electrical impedance divider, the two measurement methods have the following major problems:

in the aspect of measuring the TEV by using an electric field probe, the measurement result of the method has important theoretical significance and practical value for substation electromagnetic interference analysis, but the method does not directly measure the value of the TEV; in the aspect of using a resistive impedance voltage measuring device, the method can preliminarily realize the TEV measurement, but the potential reference point is selected to the grounding bar under the GIS base by the measuring method, and the potential of the grounding grid is also raised in the transient process, so the potential reference point selecting mode is favorable for researching the contact voltage of the GIS shell to the human body, but the potential reference point is selected at the position, far away from the GIS, of which the potential is close to the zero point to analyze the interference to the secondary equipment. To sum up: the existing method for measuring TEV only measures the potential difference of the GIS shell to the grounding bar under the base, but does not fully research the potential difference between the GIS shell and the grounding grid relative to the position where the potential is close to zero. High-frequency grounding current generated by GIS switching operation can cause the transient ground potential of the main grounding grid to rise, so that serious disturbance voltage is generated in a secondary cable, and accurate measurement and analysis of the Transient Ground Potential Rise (TGPR) of the grounding grid are also needed.

Therefore, a method for simply and accurately measuring TEV and TGPR in a GIS (geographic information System) transformer substation is urgently needed so as to research the electromagnetic transient phenomenon of the GIS transformer substation.

Disclosure of Invention

The present invention is directed to solving the above problems of the prior art. A simple, accurate method of measuring TEV and TGPR in a gas insulated substation is presented. The technical scheme of the invention is as follows:

a method of measuring TEV and TGPR in a gas insulated substation comprising the steps of:

1) and selecting the type of a high-voltage probe and the type of an automatic signal acquisition card, wherein the high-voltage probe is used for acquiring the voltage of a measuring point. And selecting the type of the high-voltage probe according to the amplitude absolute value and the main frequency of the TEV, wherein the withstand voltage value and the bandwidth of the selected high-voltage probe are respectively greater than the amplitude absolute value and the main frequency of the TEV. The signal automatic acquisition card is used for acquiring voltage data on the high-voltage probe. And (3) selecting the type of the automatic signal acquisition card according to the number of the measuring points and the TEV main frequency, wherein the number of acquisition channels and the bandwidth of the selected automatic signal acquisition card are respectively greater than the number of the measuring points and the TEV main frequency, and the sampling frequency of the selected automatic signal acquisition card is greater than 8 times of the TEV main frequency. The selected high-voltage probe and the signal automatic acquisition card are placed in a relay protection chamber to reduce electromagnetic disturbance. 2) And selecting a proper voltage measuring point and a proper zero potential reference point, wherein the zero potential reference point is selected at a grounding outgoing line in the relay protection chamber.

3) The potential of a measuring point is led to one end of a high-voltage probe in a relay protection chamber for input by using a shielding wire, the potential of an internal connecting point of the relay protection chamber is led to the other end of the high-voltage probe for input by using a grounding wire, and then an output signal of the high-voltage probe is connected to an automatic signal acquisition card.

4) Acquiring acquired voltage data from a signal automatic acquisition card, carrying out differential dispersion on a time domain of a telegraph equation according to a transmission line telegraph equation mathematical model, establishing a first-order differential equation system of a space, and then calculating by adopting a fine integral method to obtain transmission line transient response. And correcting the high-frequency loss of the measured voltage on the transmission line by using a transmission line transient response formula to finally obtain an accurate measured voltage value.

Further, the step 2) selects a proper voltage measuring point and a proper zero potential reference point, and the selection of the proper measuring point meets the following basic conditions: firstly, voltage response can be obtained for the operation of a circuit breaker or a disconnecting switch on a branch where a measuring point is located; the maximum voltage value can be measured, and the potential rise of the GIS shell and the transient ground potential rise can be measured; the measurement path comprises a disturbance voltage transmission path of a GIS shell, a voltage transformer and a control cubicle; and fourthly, reducing the distance between the voltage measuring point and the zero potential reference point.

Further, the step 3) specifically includes the following contents: when measuring a potential difference TEV (potential energy transfer) of a GIS shell relative to a grounding point of a relay protection cell, the potential of the GIS shell is led to one end of a high-voltage probe in the relay protection cell for input by using a shielding wire, the potential of the grounding point in the relay protection cell is led to the other end of the high-voltage probe in the relay protection cell for input by using a grounding wire, and then an output signal of the high-voltage probe is accessed into an automatic signal acquisition card; when the transient state ground potential rise value TGPR at a certain position is measured, the potential at the grounding downlead at the position is led to one end of the high-voltage probe in the relay protection chamber by using the shielding wire for input, the potential at the grounding point in the relay protection chamber is led to the other end of the high-voltage probe in the relay protection chamber by using the grounding wire for input, and then the output signal of the high-voltage probe is connected into the acquisition card. The shielded wire used in the measurement needs to be elevated by an insulating rod on a path leading to the relay protection chamber, and is shielded.

Further, in the step 4), because the TEV and TGPR frequencies generated during the GIS switching operation are high, a skin effect is generated on the shielded wire, which results in that the amplitude and phase of the signal are related to the length and diameter of the conductive wire, that is, a transmission line effect is generated, at this time, the shielded wire is equivalent to a transmission line, and for convenience of analysis, a partial differential hyperbolic equation system-telegraph equation is adopted as a mathematical model for describing the relationship between the transmission line voltage and the current, that is:

wherein R, L, C and G are respectively the resistance, inductance, capacitance and conductance of the transmission line in unit length, u (x, t) and i (x, t) are respectively the voltage and current on the transmission line;

the equations (1) and (2) are discretized in the time domain:

where Δ t is t/M, t is the width of the time interval under study, and M is the number of discrete points; u. of_k＝u(x,kΔt)；i_kI (x, k Δ t), x representing the spatial coordinates, k being 0,1,2 … M;

writing equations (3), (4) as a matrix form:

X＝(u₁,...,u_M,i₁,...,i_M)^T

h, F and X are introduced mainly to convert a first-order differential equation system obtained by differential dispersion of a telegraph equation in a time domain into a matrix form, wherein X represents a column vector consisting of voltage and current variables at M time discrete points at a spatial position X on a transmission line. u. of_MRepresenting the voltage, u, at spatial position x on the transmission line at time M Δ t₀Representing the voltage, i, at a spatial position x on the transmission line at time zero₀Representing the current at spatial position x on the transmission line at time zero.

The solution of equation (5) is:

epsilon represents a column vector consisting of voltage and current quantity at each time discrete point on the transmission line at the zero space coordinate position represented by an integral variable X (0).

Let the space step be Δ x, then:

x_j＝jΔx j＝0,1,2,… (7)

where exp (H.DELTA.x) is calculated as follows:

additive theorem using exponential function

exp(H·Δx)＝[exp(H·Δx/m)]^m (8)

Generally, m is 2^NN is 20, thereforeFor the time segment of β ═ Δ x/m, Taylor expansion is performed with

exp(H·β)≈1+H·β+(H·β)²/2+(H·β)³/3！+(H·β)⁴/4！＝1+T_a (9)

In the formula

T_a＝H·β+(H·β)²/2+(H·β)³/3！+(H·β)⁴/4！ (10)

Decomposition of formula (8)

This decomposition proceeds n times in total, again because

(1+T_a)×(1+T_a)＝1+2T_a+T_a×T_a (12)

Therefore, the expression (11) corresponds to the following expression

for(iter＝0；iter<N；iter++)

T_a＝2T_a+T_a×T_a (13)

When the circulation is over

T＝1+T_a (14)

The above loop calculation flow can be represented by fig. 4.

(10) The formulas (13), (14) are the fine calculation formulas of exp (H delta x), and it can be seen that the recursion calculation is carried out according to the formula (13), and 1 is excluded from participating in the addition operation;

according to the formula (7), as long as the voltage and the current of a certain point on the transmission line in a certain time period are known, the voltage and the current of any point on the transmission line in the time period can be obtained, the calculation adopts a recursion mode, the collected voltage data is obtained from the signal automatic acquisition card, the measured voltage data is corrected according to the formula (7), and finally, an accurate measured voltage value is obtained.

The invention has the following advantages and beneficial effects:

the invention mainly provides a method for measuring TEV and TGPR in a gas insulated substation more simply and accurately. The conventional measuring method adopts a relatively complex electrical impedance voltage divider device, and the method adopts simple equipment such as a high-voltage probe and an automatic signal acquisition card, so that the operation is simple and more economic; the invention selects the potential reference point at the grounding outgoing line in a relay protection chamber (the potential is close to zero and constant) and corrects the high-frequency loss of the measured voltage on the transmission line innovatively according to a mathematical model of the transmission line to finally obtain accurate measured voltage data. The invention accurately measures TEV and TGPR data, is beneficial to analyzing the electromagnetic interference problem of secondary equipment of a GIS transformer substation, and has great reference value for field and scientific research personnel to measure and master TEV and TGPR characteristics.

Drawings

FIG. 1 is a general wiring diagram for TEV and TGPR measurement of a GIS substation according to the preferred embodiment of the invention;

FIG. 2 is a concrete wiring diagram of TEV and TGPR measurement site;

FIG. 3 is a voltage waveform of a single closed sleeve measuring point of a GIS substation disconnecting switch;

FIG. 4 is a flowchart of loop calculation;

FIG. 5 is a diagram of the apparatus for measuring TEV and TGPR data.

Detailed Description

The technical solutions in the embodiments of the present invention will be described in detail and clearly with reference to the accompanying drawings. The described embodiments are only some of the embodiments of the present invention.

The technical scheme for solving the technical problems is as follows:

the invention firstly selects the type of the high-voltage probe and the automatic signal acquisition card according to the characteristics of TEV and TGPR, and selects a proper measuring point. When selecting measuring points, the following basic conditions need to be met:

(1) a voltage response can be obtained for the circuit breaker or disconnector operation on the branch.

(2) The maximum voltage value can be measured, and the potential rise of the GIS shell and the transient ground potential rise can be measured.

(3) The measurement path comprises a disturbance voltage propagation path of a GIS shell, a voltage transformer and a control cubicle.

(4) The distance between the voltage measurement point and the zero potential reference point is reduced.

After the equipment model selection and the measuring point selection are completed, the high-voltage probe and the automatic signal acquisition card are placed in the relay protection chamber to reduce electromagnetic disturbance, and an internal connection point of the relay protection chamber is used as a zero potential reference point. When the potential difference of the GIS shell relative to the internal connection point of the relay protection cell is measured, the potential of the GIS shell is led to one end of a high-voltage probe in the relay protection cell for input by using an insulated wire, the potential of the internal connection point of the relay protection cell is led to the other end of the high-voltage probe for input by using a grounding wire, and then a probe output signal is connected into an acquisition card, so that the potential difference between the potential of the GIS shell and a reference zero potential in the relay protection cell is obtained. When the transient earth potential at a certain position is measured to rise, the basic principle is the same as the above, and only the measuring point is connected to the lower end of the grounding down conductor at the position. The insulated wire used in the measurement needs to be elevated by an insulated rod on a path leading to the relay protection chamber, and shielding treatment is carried out to reduce the influence of the earth on the measurement accuracy. The overall measurement scheme is shown in figure 1.

Taking the outlet sleeve measuring point of a certain GIS substation as an example, 2 high-voltage probes are arranged for measuring: cannula-relay protection cubicle; the bushing ground down-line-relay protection cell voltage, field layout is shown in fig. 2. And carrying out single-time closing operation on the GIS substation isolating switch, and acquiring a voltage signal from the automatic signal acquisition card. Taking the casing test point as an example, the measured voltage waveform is shown in fig. 3.

And finally, correcting the measured voltage data according to the transmission line mathematical model to finally obtain an accurate measured voltage value.

It should also be noted that 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 like elements in a process, method, article, or apparatus that comprises the element.

The above examples are to be construed as merely illustrative and not limitative of the remainder of the disclosure. After reading the description of the invention, the skilled person can make various changes or modifications to the invention, and these equivalent changes and modifications also fall into the scope of the invention defined by the claims.