CN114002547A - Secondary multipoint earth fault judgment equipment and analysis algorithm for mutual inductor - Google Patents
Secondary multipoint earth fault judgment equipment and analysis algorithm for mutual inductorDownload PDFInfo
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- CN114002547A CN114002547ACN202111241917.7ACN202111241917ACN114002547ACN 114002547 ACN114002547 ACN 114002547ACN 202111241917 ACN202111241917 ACN 202111241917ACN 114002547 ACN114002547 ACN 114002547A
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- 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
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Abstract
Description
Technical Field
The invention relates to the field of transformer substation secondary circuit measurement, in particular to a secondary multipoint ground fault judgment device and an analysis algorithm for a mutual inductor.
Background
The national grid company clearly stipulates in twenty-five key requirements for preventing electric power production accidents and GB/T14285 technical regulations for relay protection and safety automatic devices: the PT secondary loop only allows 1 point to be grounded, and the grounding point is preferably arranged in the control room; independent PT without electric connection with other mutual inductors can realize 1-point grounding in a switch factory.
When the N600 lines are grounded in the switch field and the control room respectively, if a short-circuit fault or a lightning stroke event occurs in a system, a transformer substation grounding grid may generate a large fault current, and a relatively obvious potential difference occurs at two ends of two N600 grounding points of the switch field and the control room, so that a phase deviation of neutral point voltage is caused, and amplitude and phase of voltage and zero sequence voltage are influenced, thereby causing distance protection in a relay protection device, and the rejection and misoperation of zero sequence direction protection.
If the N600 grounding loop is in poor contact or the switch is broken, the voltage phase of the neutral point is shifted. The regulations stipulate that on the voltage transformer switching screen of the control room, the grounding of the secondary winding must be connected to the grounding copper bar of the screen cabinet through respective leads, and the serial connection method cannot be adopted. Although various regulations define the wiring method of the N600 grounding wire in the currently running transformer substation, the number of secondary common loops of PT for relay protection is gradually increased due to the updating and transformation of internal equipment of the transformer substation, the updating of a field voltage transformer, a current transformer, protection equipment and the like, and the multipoint ground fault phenomenon is mainly caused by the following main reasons.
If the experience of constructors is insufficient, the secondary N line of each voltage transformer is grounded directly by mistake;
secondary cable insulation aging or animal bite damage cable insulation layer to cause grounding;
the discharge of the neutral point of the switching field secondary winding is intermittent or the zinc oxide valve plate is broken down to cause grounding.
The existing multipoint ground fault judging technology has the following problems:
1) the function is incomplete, the normal operation of the secondary system can be influenced, only whether a fault occurs or not can be judged, the fault point cannot be judged, and in addition, 50Hz is injected, the normal operation of the secondary system can be influenced, and the measurement error of a metering loop can be brought;
2) the operation is complex, the field is difficult to implement, the invention needs to pull each phase of each PT to connect the cable to the device, because the number of the transformer substations PT is large and the PT are distributed at different positions of the transformer substations, the operation is extremely complex, in addition, the device can not be implemented in an operating state, and the transformer substations need to be powered off for operation;
3) some of the inventive criteria are too complex and unreliable and not conducive to circuit and program implementation.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides a secondary multipoint earth fault judgment device and an analysis algorithm for a mutual inductor,
in order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a secondary multipoint earth fault judging device for a mutual inductor, which comprises
The signal generator collects current injected into the N600 line through the first Hall current sensor;
the secondary output of the first Hall current sensor passes through a low-pass filter and then enters a microcontroller chip;
the microcontroller chip collects primary low-frequency small current signals.
Further, after receiving a sampling start command sent by the signal collector, the signal generator starts a timer to start sampling;
and after the data of 256 points are collected, stopping the timer, storing the data in an SRAM (static random access memory) in the microcontroller chip, waiting for receiving a data reading command of a signal collector, and sending the data out through an SI4432 chip connected with an SPI (serial peripheral interface) of the microcontroller chip after receiving the command.
Further, also comprises
And the signal collector is used for collecting a current signal on a secondary N600 line branch of the mutual inductor through the second Hall current sensor, and a secondary output of the second Hall current sensor enters the microcontroller chip after passing through the low-pass filter.
Further, after the signal collector sends a sampling start command to the signal generator through an SI4432 chip connected with the microcontroller chip, the signal collector starts sampling.
Further, after the signal collector collects enough 256 points of data, the timer is stopped, and the data are stored in an SRAM of the microcontroller chip.
The invention also provides a secondary multipoint ground fault judgment analysis algorithm for the mutual inductor, which is realized by equipment, and is used for sending a data reading command to the signal generator, setting 256 points of data collected by the signal collector as x (n) after receiving 256 sampling data sent by the signal generator, setting the 256 points of data sent by the signal generator as y (n), and carrying out signal processing according to the following procedures;
s1, according to each group of 64-point data, performing multiple singular value decomposition on the sampling sequences x (n), y (n) respectively;
let k be 1, then construct Hk matrix in Hankel matrix form from the sampling sequence:
wherein HakIs an approximate matrix, reflecting the main components of the signal; hdkFor the detail matrix, the detail components of the signal are reflected, and an approximate signal A is obtainedkAnd a detail signal Dk；
Wherein, in the formula:
let k be k +1 and Hk be AkRepeating the above process until k is 6, wherein the noise component is small;
s2, selecting the D obtained in the S1kThe first singular signal moment in (b) is a time starting point, and then a obtained in the previous step is taken as a according to the time starting pointkSelecting 64 values for subsequent correlation analysis;
s3, calculating by product distance correlation coefficient method
Wherein, M is the recording length of the related signal, and 64 is taken; x and y are signal vectors respectively; x is the number ofmAnd ymThe m-th elements of the x and y vectors, respectively;
and
the average of each element of x and y, respectively;
s4, in order to solve errors caused by asynchronism of two groups of data sampling, the x vector is unchanged, a data point is moved in a forward direction of a y vector data window, cross correlation coefficients Pij are obtained through calculation, 64 times of data window movement of the y vector is carried out, 64 cross correlation coefficients Pij are obtained, and the largest cross correlation coefficient Pij is selected as the final judgment basis.
Further, the value range of the cross-correlation coefficient Pij is [ -1,1 ];
+1 indicates 100% positive correlation of the two signals, -1 indicates 100% negative correlation of the two signals;
0 means zero correlation, i.e. the two signals are completely independent and have no relation;
and if the cross correlation coefficient of the two groups of data is more than 0.8, the branch where the signal collector is located is considered to have a multipoint ground fault.
The invention has the beneficial effects that: the injected low-frequency small signal does not cause frequency deviation because of the distributed capacitance of the secondary N600 line of the transformer (the lower the frequency is, the larger the impedance of the capacitance is), and the signal is not distorted.
The injected low-frequency small signals cannot influence the measurement result of the relay protection device of the transformer substation, cannot cause misoperation of the relay protection device, and cannot cause measurement errors of the metering device, because the low-frequency small signals cannot be coupled through sampling transformers in the devices, and the built-in transformers are suitable for signal measurement of 50Hz and above
And the noise in the sampled data is reduced and the signal-to-noise ratio is greatly improved by adopting a multi-time singular value decomposition method. Making the criterion margin higher.
And the influence of zero drift of current sampling is eliminated by adopting a Pearson product distance correlation coefficient method, and whether multipoint ground faults occur or not and the fault points are judged in a frequency domain range. Therefore, the problems that when the amplitude is used for judgment, and multipoint grounding possibly exists, each branch has a shunting function and current amplitude data are unstable are solved, and when the multipoint grounding exists, the frequency of a current signal is unchanged.
By adopting cross-correlation calculation, the problem that fault judgment is possibly misjudged due to the existence of N600 line current caused by the three-phase imbalance of the line can be avoided.
Drawings
FIG. 1 is a flowchart of the signal generator process of the present invention;
FIG. 2 is a flowchart of the signal detector process of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 1 and 2, a secondary multipoint ground fault determining apparatus for a transformer includes
The signal generator collects current injected into the N600 line through the first Hall current sensor;
the secondary output of the first Hall current sensor passes through a low-pass filter and then enters a microcontroller chip;
the microcontroller chip collects primary low-frequency small current signals.
After the signal generator receives a sampling starting command sent by the signal collector, a timer is started to start sampling;
and after the data of 256 points are collected, stopping the timer, storing the data in an SRAM (static random access memory) in the microcontroller chip, waiting for receiving a data reading command of a signal collector, and sending the data out through an SI4432 chip connected with an SPI (serial peripheral interface) of the microcontroller chip after receiving the command.
The secondary output of the second Hall current sensor passes through the low-pass filter and then enters the microcontroller chip.
And after the signal collector sends a sampling starting command to the signal generator through an SI4432 chip connected with the microcontroller chip, the signal collector starts sampling.
And after the signal collector collects enough 256 points of data, the timer is stopped, and the data are stored in an SRAM of the microcontroller chip.
The specific implementation mode of the invention is that the signal generator is responsible for injecting low-frequency small signals of 0.5Hz and 10mA into a secondary N600 line of the transformer, meanwhile, the signal generator collects the current injected into the N600 line through the first Hall current sensor, the secondary output of the Hall current sensor 1 enters a 12-bit analog-to-digital converter pin integrated with a microcontroller chip MSP430F5438A after passing through a low-pass filter with-3 db cut-off frequency of about 0.3Hz, which is composed of a 20k omega resistor and a 27uf capacitor, and the interrupt cycle time of the MSP430F5438A Timer _ A is set as 31.25ms. in an interrupt service program of the Timer, so as to collect the low-frequency small current signals once.
After receiving a sampling start command sent by the signal collector, the signal generator starts a Timer _ a to start sampling. And when the data of 256 points are collected, stopping the Timer _ A, storing the data in an SRAM (static random access memory) in the micro-controller chip MSP430F5438A, waiting for receiving a data reading command of the signal collector, and sending the data out through an SI4432 chip connected with an SPI (serial peripheral interface) of the micro-controller chip MSP430F5438A after receiving the command.
The signal collector collects current signals on a secondary N600 line branch of the transformer through the second Hall current sensor, the secondary output of the Hall current sensor 2 enters a 12-bit analog-to-digital converter pin integrated by a microcontroller chip MSP430F5438A after passing through a low-pass filter which is composed of a 20k omega resistor and a 27uf capacitor and has a-3 db cutoff frequency of about 0.3Hz, and the interrupt cycle time of the MSP430F5438A Timer _ A is set to be 31.25ms. in an interrupt service program of the Timer, and the low-frequency small current signals are collected once. After the signal collector sends a sampling start command to the signal generator through the SI4432 chip connected with the SPI interface of the microcontroller chip MSP430F5438A, the signal collector itself starts sampling, and stops the Timer _ A after collecting enough 256 points of data, and stores the data in the SRAM inside the microcontroller chip MSP430F 5438A.
The utility model provides a be used for mutual-inductor secondary multiple spot earth fault to judge analysis algorithm realizes through equipment which characterized in that: sending a data reading command to a signal generator, setting 256 points of data collected by a signal collector as x (n) after receiving 256 sampling data sent by the signal generator, setting the 256 points of data sent by the signal generator as y (n), and carrying out signal processing according to the following flow;
s1, according to each group of 64-point data, performing multiple singular value decomposition on the sampling sequences x (n), y (n) respectively;
let k be 1, then construct Hk matrix in Hankel matrix form from the sampling sequence:
wherein HakIs an approximate matrix, reflecting the main components of the signal; hdkFor the detail matrix, the detail components of the signal are reflected, and an approximate signal A is obtainedkAnd a detail signal Dk；
Wherein, in the formula:
let k be k +1 and Hk be AkRepeating the above process until k is 6, wherein the noise component is small;
s2, selecting the D obtained in the S1kThe first singular signal moment in (b) is a time starting point, and then a obtained in the previous step is taken as a according to the time starting pointkSelecting 64 values for subsequent correlation analysis;
s3, calculating by product distance correlation coefficient method
Wherein, M is the recording length of the related signal, and 64 is taken; x and y are signal vectors respectively; x is the number ofmAnd ymThe m-th elements of the x and y vectors, respectively; x-and Y-are the average values of the respective elements of X and Y, respectively;
s4, in order to solve errors caused by asynchronism of two groups of data sampling, the x vector is unchanged, a data point is moved in a forward direction of a y vector data window, cross correlation coefficients Pij are obtained through calculation, 64 times of data window movement of the y vector is carried out, 64 cross correlation coefficients Pij are obtained, and the largest cross correlation coefficient Pij is selected as the final judgment basis.
The value range of the cross-correlation coefficient Pij is [ -1,1 ];
+1 indicates 100% positive correlation of the two signals, -1 indicates 100% negative correlation of the two signals;
0 means zero correlation, i.e. the two signals are completely independent and have no relation;
and if the cross correlation coefficient of the two groups of data is more than 0.8, the branch where the signal collector is located is considered to have a multipoint ground fault.
The above-mentioned embodiments only express the embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (7)
1. The utility model provides a be used for mutual-inductor secondary multiple spot earth fault decision equipment which characterized in that: comprises that
The signal generator collects current injected into the N600 line through the first Hall current sensor;
the secondary output of the first Hall current sensor passes through a low-pass filter and then enters a microcontroller chip;
the microcontroller chip collects primary low-frequency small current signals.
2. The secondary multipoint ground fault determining apparatus for mutual inductor according to claim 1, characterized in that: after the signal generator receives a sampling starting command sent by the signal collector, a timer is started to start sampling;
and after the data of 256 points are collected, stopping the timer, storing the data in an SRAM (static random access memory) in the microcontroller chip, waiting for receiving a data reading command of a signal collector, and sending the data out through an SI4432 chip connected with an SPI (serial peripheral interface) of the microcontroller chip after receiving the command.
3. The secondary multipoint ground fault determination device for the mutual inductor according to claim 2, characterized in that: also comprises
And the signal collector is used for collecting a current signal on a secondary N600 line branch of the mutual inductor through the second Hall current sensor, and a secondary output of the second Hall current sensor enters the microcontroller chip after passing through the low-pass filter.
4. The apparatus according to claim 3, wherein: and after the signal collector sends a sampling starting command to the signal generator through an SI4432 chip connected with the microcontroller chip, the signal collector starts sampling.
5. The device for determining the secondary multipoint ground fault of the mutual inductor according to claim 4, wherein: and after the signal collector collects enough 256 points of data, the timer is stopped, and the data are stored in an SRAM of the microcontroller chip.
6. A secondary multipoint earth fault decision analysis algorithm for a transformer implemented by the apparatus of any of claims 1 to 5, characterized by: sending a data reading command to a signal generator, setting 256 points of data collected by a signal collector as x (n) after receiving 256 sampling data sent by the signal generator, setting the 256 points of data sent by the signal generator as y (n), and carrying out signal processing according to the following flow;
s1, according to each group of 64-point data, performing multiple singular value decomposition on the sampling sequences x (n), y (n) respectively;
let k be 1, then construct Hk matrix in Hankel matrix form from the sampling sequence:
wherein HakIs an approximate matrix, reflecting the main components of the signal; hdkFor the detail matrix, the detail components of the signal are reflected, and an approximate signal A is obtainedkAnd a detail signal Dk；
Wherein, in the formula:
let k be k +1 and Hk be AkRepeating the above process until k is 6, wherein the noise component is small;
s2, selecting the D obtained in the S1kThe first singular signal moment in (b) is a time starting point, and then a obtained in the previous step is taken as a according to the time starting pointkSelecting 64 values for subsequent correlation analysis;
s3, calculating by product distance correlation coefficient method
Wherein, M is the recording length of the related signal, and 64 is taken; x and y are signal vectors respectively; x is the number ofmAnd ymThe m-th elements of the x and y vectors, respectively;
and
the average of each element of x and y, respectively;
s4, in order to solve errors caused by asynchronism of two groups of data sampling, the x vector is unchanged, a data point is moved in a forward direction of a y vector data window, cross correlation coefficients Pij are obtained through calculation, 64 times of data window movement of the y vector is carried out, 64 cross correlation coefficients Pij are obtained, and the largest cross correlation coefficient Pij is selected as the final judgment basis.
7. The secondary multipoint earth fault decision analysis algorithm for the mutual inductor according to claim 6, wherein:
the value range of the cross-correlation coefficient Pij is [ -1,1 ];
+1 indicates 100% positive correlation of the two signals, -1 indicates 100% negative correlation of the two signals;
0 means zero correlation, i.e. the two signals are completely independent and have no relation;
and if the cross correlation coefficient of the two groups of data is more than 0.8, the branch where the signal collector is located is considered to have a multipoint ground fault.
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Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20080215278A1 (en)* | 2006-07-14 | 2008-09-04 | Square D Company | Method and system of calibrating sensing components in a circuit breaker system |
| CN102621451A (en)* | 2012-03-28 | 2012-08-01 | 北京水木源华电气有限公司 | Distribution line single-phase grounding fault detecting method and system based on instantaneous signal method |
| CN103454528A (en)* | 2013-08-30 | 2013-12-18 | 华南理工大学 | Method for detecting and identifying electric system element fault based on form singular entropy |
| CN103513150A (en)* | 2013-09-17 | 2014-01-15 | 广东电网公司东莞供电局 | Device and method for detecting multipoint earthing of voltage transformer for electric system |
| CN104360215A (en)* | 2014-11-12 | 2015-02-18 | 江苏省电力公司淮安供电公司 | Detection device for multi-point earthing fault of small bus N600 |
| CN105486975A (en)* | 2015-11-20 | 2016-04-13 | 国家电网公司 | Single-phase earth fault detection method of 10kV distribution network |
| CN108535572A (en)* | 2018-05-10 | 2018-09-14 | 长沙理工大学 | Metering system secondary circuit monitoring method and device based on fundamental wave zero sequence feature |
| CN113253047A (en)* | 2021-04-19 | 2021-08-13 | 南京南瑞继保电气有限公司 | Single-phase grounding line selection method and device, electronic equipment and storage medium |
- 2021
- 2021-10-25CNCN202111241917.7Apatent/CN114002547B/enactiveActive
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20080215278A1 (en)* | 2006-07-14 | 2008-09-04 | Square D Company | Method and system of calibrating sensing components in a circuit breaker system |
| CN102621451A (en)* | 2012-03-28 | 2012-08-01 | 北京水木源华电气有限公司 | Distribution line single-phase grounding fault detecting method and system based on instantaneous signal method |
| CN103454528A (en)* | 2013-08-30 | 2013-12-18 | 华南理工大学 | Method for detecting and identifying electric system element fault based on form singular entropy |
| CN103513150A (en)* | 2013-09-17 | 2014-01-15 | 广东电网公司东莞供电局 | Device and method for detecting multipoint earthing of voltage transformer for electric system |
| CN104360215A (en)* | 2014-11-12 | 2015-02-18 | 江苏省电力公司淮安供电公司 | Detection device for multi-point earthing fault of small bus N600 |
| CN105486975A (en)* | 2015-11-20 | 2016-04-13 | 国家电网公司 | Single-phase earth fault detection method of 10kV distribution network |
| CN108535572A (en)* | 2018-05-10 | 2018-09-14 | 长沙理工大学 | Metering system secondary circuit monitoring method and device based on fundamental wave zero sequence feature |
| CN113253047A (en)* | 2021-04-19 | 2021-08-13 | 南京南瑞继保电气有限公司 | Single-phase grounding line selection method and device, electronic equipment and storage medium |
Non-Patent Citations (2)
| Title |
|---|
| 王斌;方青;薛玉峰;程志辉;: "小波变换在直流接地故障检测中的应用及其在LabVIEW平台的实现", 制造业自动化, no. 14, pages 105 - 108* |
| 王韶;朱姜峰;: "基于改进相关性分析法的配电网络单相接地故障选线", 电力系统保护与控制, no. 15, pages 76 - 81* |
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