CN111123033B - Distribution line potential fault identification method - Google Patents
Distribution line potential fault identification method Download PDFInfo
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- CN111123033B CN111123033B CN201911333195.0A CN201911333195A CN111123033B CN 111123033 B CN111123033 B CN 111123033B CN 201911333195 A CN201911333195 A CN 201911333195A CN 111123033 B CN111123033 B CN 111123033B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/088—Aspects of digital computing
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Abstract
The invention provides a distribution line potential fault identification method, which comprises the following steps: acquiring a three-phase power frequency voltage signal, a three-phase power frequency current signal, a three-phase voltage traveling wave signal and state information of each switch of a circuit in real time; detecting whether the traveling wave is started or not according to the three-phase voltage traveling wave and the three-phase current traveling wave; judging whether the disturbance is positioned in the area or not according to the polarities of the zero-mode voltage initial traveling wave and the zero-mode current initial traveling wave; judging the disturbance type by using the three-phase power frequency voltage and the state information of the switch; by the fault identification method, the frequency of single-phase grounding short-circuit faults caused by potential faults can be effectively reduced, the blind maintenance of lines is reduced, and the operation and maintenance efficiency of the distribution network is improved.
Description
Technical Field
The invention relates to the technical field of power systems, in particular to a distribution line potential fault identification method utilizing power frequency, traveling wave and switch state information.
Background
The latent fault is not a kind of fault per se, but the latent fault is very easy to cause an actual fault in a continuously severe operating environment, and the safe power supply of the network is influenced. In the context of the distribution network studied by the present invention, the most common potential fault is a localized breakdown caused by a defect in the insulation of the cable lines. With the continuous development and upgrading and reconstruction of power distribution networks, cable lines are the mainstream of distribution lines and occupy the vast majority.
The laying environment of the power cable line in China is generally located in an underground trench, air is relatively humid, and the buried depth of the trench is close to the ground. In such an external operating environment, the external insulation of the cable line is very easily damaged, for example, the damp air gradually erodes the external insulation layer to cause the insulation aging of the cable, and the buried ground is easy to cause other construction operations to damage the cable and even directly cause the cable to break down so as to exit the operation. It should be noted that, in general, a long cable line is formed by splicing a plurality of cables, and at a cable joint, the insulation capability of the cable is relatively weak, and the cable is also a part of the cable with frequent fault.
After the cable line insulation is gradually damaged, even under a normal operating voltage level, transient breakdown, namely a short-circuit to ground phenomenon easily occurs at an insulation deterioration part, although the short-circuit to ground is only transient and transient, a large short-circuit current is generated in the transient process of the short-circuit, and further damage is caused to the external insulation of the cable. Repeated and continuous transient breakdown can gradually destroy the external insulation of the cable line until the external insulation destruction causes a permanent single-phase earth fault. It is worth noting that if the external insulation level of the adjacent cable lines is also poor, a single-phase earth fault is very likely to develop into a two-phase interphase short circuit, which will have a greater impact on the distribution lines, the supply loads and the distribution network.
The method is characterized in that a non-effective grounding mode is adopted at the neutral point of a power distribution network of 35kV or below in China, so that if a single-phase grounding short-circuit fault occurs in the network, the fault current has no path, and the current in a line cannot be increased rapidly. On the contrary, the voltage of the fault phase tends to the ground voltage, the voltage of the non-fault phase rises to the line voltage, the insulation of the cable line of the non-fault phase is tested, even the damage is caused, especially when the cable line of the non-fault phase has insulation defects, the single-phase ground fault is easy to gradually develop into the phase-to-phase fault, the safe power supply of the power distribution network is further influenced, and the health of the equipment is threatened.
It is known that potential faults such as cable line insulation defects have a significant impact on the health of the distribution network and its normal operation. Therefore, the success of identifying potential faults in distribution lines is of extraordinary and reluctant significance.
Disclosure of Invention
The invention aims to at least solve one of the technical problems in the prior art and provides a distribution line potential fault identification method by using power frequency, traveling wave and switch state information.
The invention discloses a distribution line potential fault identification method, which comprises the following steps:
s1, arranging measuring points at all switches on the distribution line, and measuring a three-phase power frequency voltage signal, a three-phase power frequency current signal, a three-phase voltage traveling wave signal and state information of each switch of the line in real time, wherein the traveling wave sampling frequency is 2MHz, and the power frequency sampling frequency is 1 KHz;
s2, judging whether the collected traveling wave signal exceeds a threshold value in real time, and if any traveling wave in the three-phase voltage traveling wave or the three-phase current traveling wave exceeds the threshold value, judging that the traveling wave is started;
s3, if the traveling wave is started, respectively judging the disturbance position of each section of the feeder line, and judging whether the disturbance position is located in the section, if so, executing the step S4;
and S4, judging and analyzing the disturbance type by using the three-phase power frequency voltage acquired by the corresponding measuring point of the section and the state information of the switch, and identifying whether the section is a potential fault.
Preferably, in step S3, the strategy for determining the disturbance position in each segment is: synthesizing a zero-mode voltage traveling wave by using the three-phase voltage traveling wave, synthesizing a zero-mode current traveling wave by using the three-phase current traveling wave, performing wavelet transformation on the zero-mode voltage traveling wave and the zero-mode current traveling wave and calculating a modulus maximum value, specifically adopting a derivative function of a cubic center B spline function as a wavelet function, performing 4-layer wavelet transformation, expressing the polarities of the zero-mode voltage and the current initial traveling wave by using the positive and negative of the 2-layer wavelet transformation modulus maximum value, judging that the disturbance is positioned on the load side of a measurement point if the polarities of the zero-mode voltage initial traveling wave and the zero-mode current initial traveling wave are opposite, and judging that the disturbance is positioned on the power supply side of the measurement point if the polarities of the zero-mode voltage initial traveling wave and the zero-mode current initial traveling wave are the same.
Preferably, in step S3, the strategy for determining whether the disturbance position is located in the zone is as follows: starting from the power supply side, detecting a disturbance position judgment result of each measurement point, and if the first measurement point judges that the disturbance is positioned on the power supply side of the measurement point, the disturbance is not positioned on the feeder line;
if the first measuring point judges that the disturbance is positioned on the load side of the measuring point, continuously detecting the judgment result of the next measuring point;
if the second measuring point judges that the disturbance is positioned on the power supply side of the measuring point, judging that the disturbance is positioned on a line between the first measuring point and the second measuring point, if the second measuring point judges that the disturbance is positioned on the load side of the measuring point, continuously detecting the judgment result of the next measuring point, and so on, judging that the disturbance is positioned on the load side of the measuring point by the measuring point before the disturbance point, and judging that the disturbance is positioned on the power supply side of the measuring point by the measuring point after the disturbance point; and if the disturbance is still judged to be positioned on the load side of the measuring point until the last measuring point, the disturbance is positioned on the last section of line.
Preferably, in step S2, the voltage threshold is set to 5V and the current threshold is set to 2.5A for distribution lines of 35KV or less.
Preferably, the strategy for judging the disturbance type includes: based on the power frequency voltage at the outgoing line, eliminating fault disturbance and judging a fault phase; if one phase in the steady-state three-phase power frequency voltage is 0, the voltages of the other two phases are increased, the voltage changes exceed a threshold value, the threshold value is 50V, the circuit is judged to have a single-phase earth fault, and the phase with the voltage of 0 is the fault phase.
Preferably, the strategy for judging the disturbance type includes: based on the switch state information, eliminating switch disturbance, and if a switch opening signal is detected by a measuring point, judging that the switch is opened; and if the measurement point detects a switch closing signal, judging that the switch is closed.
Preferably, the strategy for judging the disturbance type includes: based on the fault phase voltage waveform, eliminating lightning stroke as fault interference, and judging the lightning stroke event if the correlation coefficients with the standard lightning voltage waveform are less than 0.5;
y is the detected disturbance voltage waveform, U is the standard lightning voltage waveform, Cov (Y, U) is the covariance of Y and U, Var [ Y ] is the variance of Y, Var [ U ] is the variance of U, and r (Y, U) is the correlation coefficient of Y and U.
Preferably, based on the disturbance frequency of the same section, a potential fault is determined, the monitoring is continuously carried out on the fault section, if the potential fault is determined to exist in the section for 3 times continuously in a specified time, the potential fault is determined to exist in the section, and further maintenance and replacement are required.
Preferably, the predetermined time is a time of 2 cycles of the power system.
The method can effectively reduce the frequency of single-phase grounding short circuit faults caused by potential faults, reduce the blind maintenance of the line and improve the operation and maintenance efficiency of the distribution network.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
Fig. 1 is a schematic flow chart of a method for identifying a potential fault of a distribution line according to an embodiment of the present invention.
Detailed Description
In order that the above objects, features and advantages of the present invention can be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings. It should be noted that the embodiments and features of the embodiments of the present application may be combined with each other without conflict.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced otherwise than as specifically described herein, and thus the scope of the present invention is not limited by the specific embodiments disclosed below.
According to one embodiment of the invention, the method for identifying the potential fault of the distribution line comprises the following steps:
s1, arranging measuring points at all switches on the distribution line, and measuring a three-phase power frequency voltage signal, a three-phase power frequency current signal, a three-phase voltage traveling wave signal and state information of each switch of the line in real time, wherein the traveling wave sampling frequency is 2MHz, and the power frequency sampling frequency is 1 KHz;
S2, judging whether the collected traveling wave signal exceeds a threshold value in real time, and if any traveling wave in the three-phase voltage traveling wave or the three-phase current traveling wave exceeds the threshold value, judging that the traveling wave is started;
s3, if the traveling wave is started, respectively judging the disturbance position of each section of the feeder line, and judging whether the disturbance position is located in the section, if so, executing the step S4;
and S4, judging and analyzing the disturbance type by using the three-phase power frequency voltage acquired by the corresponding measuring point of the section and the state information of the switch, and identifying whether the section is a potential fault.
As a preferred embodiment, in step S3, the strategy for determining the disturbance position in each segment is as follows: synthesizing a zero-mode voltage traveling wave by using the three-phase voltage traveling wave, synthesizing a zero-mode current traveling wave by using the three-phase current traveling wave, performing wavelet transformation on the zero-mode voltage traveling wave and the zero-mode current traveling wave and calculating a modulus maximum value, specifically adopting a derivative function of a cubic center B spline function as a wavelet function, performing 4-layer wavelet transformation, expressing the polarities of the zero-mode voltage and the current initial traveling wave by using the positive and negative of the 2-layer wavelet transformation modulus maximum value, judging that the disturbance is positioned on the load side of a measurement point if the polarities of the zero-mode voltage initial traveling wave and the zero-mode current initial traveling wave are opposite, and judging that the disturbance is positioned on the power supply side of the measurement point if the polarities of the zero-mode voltage initial traveling wave and the zero-mode current initial traveling wave are the same.
As a preferred embodiment, in step S3, the strategy for determining whether the disturbance position is located in the zone is: starting from the power supply side, detecting a disturbance position judgment result of each measurement point, and if the first measurement point judges that the disturbance is positioned on the power supply side of the measurement point, the disturbance is not positioned on the feeder line;
if the first measuring point judges that the disturbance is positioned on the load side of the measuring point, continuously detecting the judgment result of the next measuring point;
if the second measuring point judges that the disturbance is positioned on the power supply side of the measuring point, judging that the disturbance is positioned on a line between the first measuring point and the second measuring point, if the second measuring point judges that the disturbance is positioned on the load side of the measuring point, continuously detecting the judgment result of the next measuring point, and so on, judging that the disturbance is positioned on the load side of the measuring point by the measuring point before the disturbance point, and judging that the disturbance is positioned on the power supply side of the measuring point by the measuring point after the disturbance point; and if the disturbance is still judged to be positioned on the load side of the measuring point until the last measuring point, the disturbance is positioned on the last section of line.
In a preferred embodiment, in step S2, the voltage threshold is set to 5V and the current threshold is set to 2.5A for distribution lines of 35KV or less.
As a preferred implementation scheme, fault disturbance is eliminated and a fault phase is judged based on the power frequency voltage at the outgoing line. If one phase in the steady-state three-phase power frequency voltage is 0, the voltages of the other two phases are increased, the voltage changes exceed a threshold value, the threshold value is 50V, the circuit is judged to have a single-phase earth fault, and the phase with the voltage of 0 is the fault phase.
As a preferred embodiment, switching disturbances are excluded based on the switching state information. If the measuring point detects a switch opening signal, judging that the switch is opened; if the measuring point detects a switch closing signal, judging that the switch is closed;
as a preferred embodiment, lightning strike non-fault interference is eliminated based on a fault phase voltage waveform. The correlation coefficients with the standard lightning voltage waveform are all less than 0.5, and the lightning stroke event is judged;
y is the detected disturbance voltage waveform, U is the standard lightning voltage waveform, Cov (Y, U) is the covariance of Y and U, Var [ Y ] is the variance of Y, Var [ U ] is the variance of U, and r (Y, U) is the correlation coefficient of Y and U.
As a preferred embodiment, a potential fault is determined based on the same zone disturbance frequency. And continuously monitoring the fault section, and if the section is continuously judged to have the potential fault for 3 times within the specified time, judging that the section has the potential fault and needing further maintenance and replacement. The predetermined time is 2 cycles of the power system, and for a 50Hz power frequency system, one cycle is 20ms, so the predetermined time is 40 ms.
Fig. 1 is a schematic flow chart illustrating an implementation of the method for identifying a potential fault of a distribution line according to an embodiment of the present invention.
The method can effectively reduce the frequency of single-phase grounding short circuit faults caused by potential faults, reduce the blind maintenance of the line and improve the operation and maintenance efficiency of the distribution network.
In the description herein, the description of the terms "one embodiment," "some embodiments," "specific embodiments," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (7)
1. The method for identifying the potential fault of the distribution line is characterized by comprising the following steps of:
s1, arranging measuring points at all switches on the distribution line, and measuring a three-phase power frequency voltage signal, a three-phase power frequency current signal, a three-phase voltage traveling wave signal and state information of each switch of the line in real time, wherein the traveling wave sampling frequency is 2MHz, and the power frequency sampling frequency is 1 KHz;
s2, judging whether the collected traveling wave signal exceeds a threshold value in real time, if any traveling wave in the three-phase voltage traveling wave or the three-phase current traveling wave exceeds the threshold value, judging that the traveling wave is started, and executing the step S3;
s3, respectively judging the disturbance position of each section of the feeder line, judging whether the disturbance position is located in the section, if so, executing a step S4;
s4, carrying out disturbance type judgment and analysis by using the three-phase power frequency voltage acquired by the corresponding measuring point of the section and the state information of the switch, and identifying whether the section is a potential fault;
in step S3, the strategy for determining whether the disturbance position is located in the zone is: starting from the power supply side, detecting a disturbance position judgment result of each measurement point, and if the first measurement point judges that the disturbance is positioned on the power supply side of the measurement point, the disturbance is not positioned on the feeder line;
If the first measuring point judges that the disturbance is positioned on the load side of the measuring point, continuously detecting the judgment result of the next measuring point;
if the second measuring point judges that the disturbance is positioned on the power supply side of the measuring point, judging that the disturbance is positioned on a line between the first measuring point and the second measuring point, if the second measuring point judges that the disturbance is positioned on the load side of the measuring point, continuously detecting the judgment result of the next measuring point, and so on, judging that the disturbance is positioned on the load side of the measuring point by the measuring point before the disturbance point, and judging that the disturbance is positioned on the power supply side of the measuring point by the measuring point after the disturbance point; if the disturbance is still judged to be positioned on the load side of the measuring point until the last measuring point, the disturbance is positioned on the last section of line;
and (3) judging a potential fault based on the disturbance frequency of the same section, continuously monitoring the fault section, and if the section is continuously judged to have the potential fault for 3 times within a specified time, judging that the section has the potential fault and needing further maintenance and replacement.
2. The method for identifying the potential faults of the distribution line according to claim 1, wherein in the step S3, the strategy for determining the disturbance position in each section is as follows: synthesizing a zero-mode voltage traveling wave by using the three-phase voltage traveling wave, synthesizing a zero-mode current traveling wave by using the three-phase current traveling wave, performing wavelet transformation on the zero-mode voltage traveling wave and the zero-mode current traveling wave and calculating a modulus maximum value, specifically adopting a derivative function of a cubic center B spline function as a wavelet function, performing 4-layer wavelet transformation, expressing the polarities of the zero-mode voltage and the current initial traveling wave by using the positive and negative of the 2-layer wavelet transformation modulus maximum value, judging that the disturbance is positioned on the load side of a measurement point if the polarities of the zero-mode voltage initial traveling wave and the zero-mode current initial traveling wave are opposite, and judging that the disturbance is positioned on the power supply side of the measurement point if the polarities of the zero-mode voltage initial traveling wave and the zero-mode current initial traveling wave are the same.
3. The method of claim 1 wherein in step S2, the voltage threshold is set at 5V and the current threshold is set at 2.5A for 35KV and below distribution lines.
4. The method of claim 1, wherein the strategy for determining the type of disturbance comprises: based on the power frequency voltage at the outgoing line, eliminating fault disturbance and judging a fault phase; if one phase in the steady-state three-phase power frequency voltage is 0, the voltages of the other two phases are increased, the voltage changes exceed a threshold value, the threshold value is 50V, the circuit is judged to have a single-phase earth fault, and the phase with the voltage of 0 is the fault phase.
5. The method of claim 1, wherein the strategy for determining the type of disturbance comprises: based on the switch state information, eliminating switch disturbance, and if a switch opening signal is detected by a measuring point, judging that the switch is opened; and if the measurement point detects a switch closing signal, judging that the switch is closed.
6. The method of claim 1, wherein the strategy for determining the type of disturbance comprises: based on the fault phase voltage waveform, eliminating lightning stroke as fault interference, and judging the lightning stroke event if the correlation coefficients with the standard lightning voltage waveform are less than 0.5;
Y is the detected disturbance voltage waveform, U is the standard lightning voltage waveform, Cov (Y, U) is the covariance of Y and U, Var [ Y ] is the variance of Y, Var [ U ] is the variance of U, and r (Y, U) is the correlation coefficient of Y and U.
7. The method of claim 1 wherein the specified time is a 2 cycle time of the power system.
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| CN112630638B (en) * | 2020-11-25 | 2024-03-22 | 国网江苏省电力有限公司检修分公司 | Method and system for identifying flashover of porcelain bushing of circuit breaker |
| CN113804978B (en) * | 2021-09-01 | 2024-01-23 | 青岛鼎信通讯股份有限公司 | Lightning stroke waveform identification method based on fault indicator |
| CN114034963A (en) * | 2021-09-27 | 2022-02-11 | 国网青海省电力公司玉树供电公司 | Distribution line single-phase earth fault section identification method based on phase current variable quantity |
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