CN111830429A - Ground fault detection method and device for power system - Google Patents
Ground fault detection method and device for power system Download PDFInfo
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- CN111830429A CN111830429A CN202010566051.6A CN202010566051A CN111830429A CN 111830429 A CN111830429 A CN 111830429A CN 202010566051 A CN202010566051 A CN 202010566051A CN 111830429 A CN111830429 A CN 111830429A
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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
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/52—Testing for short-circuits, leakage current or ground faults
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- G—PHYSICS
- G04—HOROLOGY
- G04R—RADIO-CONTROLLED TIME-PIECES
- G04R20/00—Setting the time according to the time information carried or implied by the radio signal
- G04R20/02—Setting the time according to the time information carried or implied by the radio signal the radio signal being sent by a satellite, e.g. GPS
Abstract
The invention discloses a ground fault detection method of a power system, which is executed by a microcontroller, and comprises the following steps: receiving a GPS second pulse clock signal acquired by a GPS time service module, and calibrating an internal clock signal by using the GPS second pulse clock signal to obtain a high-precision timestamp; receiving zero sequence voltage data of the power system acquired by the zero sequence voltage acquisition module in real time; judging whether the power system has a ground fault according to the zero sequence voltage data; and when the power system has a ground fault, obtaining the fault occurrence time of the power system according to the zero sequence voltage data and the high-precision timestamp. The invention also discloses a corresponding device, and by implementing the method, whether the power system has the ground fault or not can be effectively judged, and when the ground fault occurs, the fault occurrence time can be accurately acquired, so that the difficulty in positioning the fault point is greatly reduced.
Description
Technical Field
The present invention relates to the field of power system technologies, and in particular, to a method and an apparatus for detecting a ground fault in a power system.
Background
With the rapid development of national economy, the scale of an electric power system is getting bigger and bigger, a network structure becomes more and more complex, and the requirement of a user on the stability of power supply is higher and higher, so that the electric power system needs to be strengthened and upgraded continuously, the fault is avoided in the running process of the system, and even if the fault occurs, the position where the fault occurs needs to be found quickly and accurately after the fault occurs, so that the fault is eliminated quickly, the safe running of the electric power system is ensured, and the loss is reduced to the minimum.
The existing power distribution network ground fault detection method mainly depends on a zero sequence voltage signal and a zero sequence current signal. And judging whether the ground fault occurs according to the detected zero sequence voltage signal at the bus of the transformer substation, and positioning a ground fault point according to the zero sequence current obtained after the three-phase current vector synthesis. To accurately locate the ground fault point, the detection precision of the fault occurring time point needs to reach the level of several mus. However, in the process of implementing the invention, the inventor finds that the prior art has at least the following problems: at present, the time synchronization is carried out between three-phase sensors by adopting a mutual correction method, the time precision is 100 mu s grade, and the precision grade is difficult to meet the requirements of high-resistance grounding fault detection and fault positioning.
Disclosure of Invention
The embodiment of the invention aims to provide a method and a device for detecting a ground fault of a power system, which can effectively judge whether the power system has the ground fault or not, accurately acquire the fault occurrence time when the ground fault occurs and greatly reduce the difficulty of fault point positioning.
In order to achieve the above object, an embodiment of the present invention provides a ground fault detection method for a power system, which is executed by a microcontroller, and the ground fault detection method for the power system includes:
receiving a GPS second pulse clock signal acquired by a GPS time service module, and calibrating an internal clock signal by using the GPS second pulse clock signal to obtain a high-precision timestamp;
receiving zero sequence voltage data of the power system acquired by the zero sequence voltage acquisition module in real time;
judging whether the power system has a ground fault according to the zero sequence voltage data;
and when the power system has a ground fault, obtaining the fault occurrence time of the power system according to the zero sequence voltage data and the high-precision timestamp.
As an improvement of the above scheme, the receiving a GPS second pulse clock signal acquired by a GPS time service module, and calibrating an internal clock signal by using the GPS second pulse clock signal to obtain a high-precision timestamp specifically includes:
acquiring a clock signal of an external active crystal oscillator;
performing primary clock frequency division on the clock signal, and taking the clock signal subjected to the primary clock frequency division as a clock source of a real-time clock chip to generate a second-level time signal;
carrying out secondary clock frequency division on the clock signal subjected to the primary clock frequency division to obtain a 1Hz clock signal;
calibrating the 1Hz clock signal by using the GPS second pulse clock signal acquired by the GPS time service module to obtain a calibrated 1Hz clock signal;
counting the calibrated 1Hz clock signal to generate a sub-second time signal;
and obtaining the high-precision timestamp according to the second-level time signal and the sub-second-level time signal.
As an improvement of the above scheme, the determining whether the power system has a ground fault according to the zero sequence voltage data specifically includes:
calculating an absolute value of the effective value of the fundamental wave amplitude of the zero sequence voltage data to be used as a zero sequence voltage amplitude index;
judging whether the zero sequence voltage amplitude index exceeds a first preset threshold value and lasts for a first preset time;
and when the zero sequence voltage amplitude index exceeds a first preset threshold value and lasts for a first preset duration, judging that the power system has a ground fault.
As an improvement of the above scheme, the determining whether the power system has a ground fault according to the zero sequence voltage data specifically includes:
obtaining effective values of fundamental waves of N previous cycles of the current cycle of the zero-sequence voltage data as a first fundamental wave effective value set;
obtaining an effective value of a fundamental wave of the (N + 1) th cycle of the current cycle of the zero-sequence voltage data as a second fundamental wave effective value;
according to the first fundamental wave effective value set and the second fundamental wave effective value, calculating a long-term voltage change index through the following calculation formula:
U＝|U1-U0|+|U2-U0|+(...)+|UN-U0|；
wherein, U1、U2...UNFor the first set of fundamental valid values, U0The second fundamental wave effective value is N is more than or equal to 1;
judging whether the long-term voltage change index exceeds a second preset threshold value or not;
and when the long-term voltage change index exceeds a second preset threshold value, judging that the power system has a ground fault.
As an improvement of the above scheme, when the power system has a ground fault, obtaining a fault occurrence time of the power system according to the zero-sequence voltage data and the high-precision timestamp, specifically includes:
calculating each voltage sampling point x in the current cycle of the zero sequence voltage dataiVoltage sampling point y corresponding to the last cycleiAs voltage sampling point increments;
according to the voltage sampling point increment, calculating a time mutation index by the following calculation formula:
wherein, Δ xiThe increment of the voltage sampling points is adopted, and M is the number of the voltage sampling points in the cycle;
when the time-varying index is judged to exceed a third preset threshold value and the absolute values of the voltage sampling point increments with continuous preset number exceed a fourth preset threshold value for the first time, determining the voltage sampling point x of the first voltage sampling point increment in the voltage sampling point increments with preset numberiThe sampling time of (1) is the time of occurrence of the fault.
As an improvement of the above, the ground fault detection method of the power system further includes:
after the fault occurrence time of the power system is obtained, the fault occurrence time of the power system is sent to a communication module, so that the communication module reports the fault occurrence time of the power system to a background.
The embodiment of the invention also provides a ground fault detection device of the power system, which comprises a microcontroller, a GPS time service module and a zero sequence voltage acquisition module; the microcontroller is respectively connected with the GPS time service module and the zero sequence voltage acquisition module; the microprocessor executes the ground fault detection method of the power system according to any one of claims 1 to 5.
As an improvement of the above, the ground fault detection apparatus of the power system further includes a communication module; the communication module is connected with the microcontroller;
the communication module is used for receiving the fault occurrence time of the power system sent by the controller after obtaining the fault occurrence time of the power system, and reporting the fault occurrence time of the power system to a background.
As an improvement of the above scheme, the ground fault detection device of the power system further includes a power supply module, and the power supply circuit is respectively connected to the microcontroller, the zero sequence voltage acquisition module and the communication module;
the power circuit is used for supplying power to the microcontroller, the zero sequence voltage acquisition module and the communication module.
As an improvement of the above solution, the ground fault detection apparatus of the power system further includes a data storage module; the data storage module is connected with the microcontroller.
Compared with the prior art, the ground fault detection method and the ground fault detection device for the power system disclosed by the invention have the advantages that the microcontroller receives the GPS second pulse clock signal acquired by the GPS time service module, and the internal clock signal is calibrated to obtain the high-precision timestamp. Meanwhile, the microcontroller receives the zero sequence voltage data of the power system acquired by the zero sequence voltage acquisition module in real time; judging whether the power system has a ground fault according to the zero sequence voltage data; and when the power system has a ground fault, obtaining the fault occurrence time of the power system according to the zero sequence voltage data and the high-precision timestamp. By acquiring the accurate fault occurrence time, the difficulty of fault point positioning can be greatly reduced in the process of fault point positioning, the fault occurring in the power system can be timely and accurately checked and solved, and the safe and stable operation of the power system is improved.
Drawings
Fig. 1 is a schematic flowchart of a ground fault detection method of an electric power system according to an embodiment of the present invention;
FIG. 2 is a flowchart illustrating the step S1 according to the first embodiment of the present invention;
fig. 3 is a schematic flow chart of step S1 in a preferred implementation manner of the first embodiment of the present invention;
FIG. 4 is a flowchart illustrating the step S3 according to an embodiment of the present invention;
FIG. 5 is a flowchart illustrating step S3 according to another embodiment of the present invention;
FIG. 6 is a flowchart illustrating the step S4 according to the first embodiment of the present invention;
fig. 7 is a schematic structural diagram of a ground fault detection apparatus of an electric power system according to a second embodiment of the present invention;
FIG. 8 is a schematic circuit diagram of a GPS time service module according to a second embodiment of the present invention;
fig. 9 is a schematic circuit structure diagram of a communication module according to a second embodiment of the present invention;
fig. 10 is a schematic circuit diagram of a power module according to a second embodiment of the invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Fig. 1 is a schematic flowchart illustrating a step of a method for detecting a ground fault of an electrical power system according to an embodiment of the present invention. The ground fault detection method for the power system provided by the embodiment of the invention comprises the following steps of S1 to S4:
s1, receiving a GPS second pulse clock signal acquired by the GPS time service module, and calibrating an internal clock signal by using the GPS second pulse clock signal to obtain a high-precision timestamp;
s2, receiving the zero sequence voltage data of the power system acquired by the zero sequence voltage acquisition module in real time;
s3, judging whether the power system has a ground fault according to the zero sequence voltage data;
and S4, when the power system has a ground fault, obtaining the fault occurrence time of the power system according to the zero sequence voltage data and the high-precision timestamp.
In an embodiment of the present invention, the ground fault detection method of the power system is performed by a Microcontroller (MCU). The GPS time service module and the zero sequence voltage acquisition module are respectively connected with the microcontroller. The GPS time service module is used for acquiring a second pulse clock signal of the GPS time service system, so that the microcontroller realizes high-precision time synchronization with the GPS time service system, a high-precision timestamp is obtained, the high-precision fault occurrence time timestamp can be obtained in the process of detecting the fault occurrence time of the power system, and the difficulty of subsequent fault positioning is reduced.
The zero sequence voltage acquisition module is used for acquiring zero sequence voltage data of the power system in real time, so that the microcontroller analyzes whether the power system fails or not and the time when the failure occurs according to the zero sequence voltage data. In one embodiment, the zero sequence voltage data is collected in a sine wave manner, the collection frequency is 12.8KHz, that is, 12.8K data is collected in one second, and each data is 2 bytes. One sine wave is 20ms and one wave takes 256 data, occupying 512 bytes.
By adopting the technical means of the embodiment of the invention, the microcontroller calibrates the internal clock signal through the GPS second pulse clock signal acquired by the GPS time service module to obtain the high-precision timestamp; judging whether the power system has ground fault according to the zero sequence voltage data acquired by the zero sequence voltage acquisition module in real time; and if the power system is judged to have the ground fault, analyzing to obtain a high-precision fault occurrence time stamp according to the zero sequence voltage data. By acquiring the accurate fault occurrence time, the difficulty of fault point positioning can be greatly reduced in the process of fault point positioning, the fault occurring in the power system can be timely and accurately checked and solved, and the safe and stable operation of the power system is improved.
As a preferred implementation manner, refer to fig. 2, which is a schematic flow chart of step S1 in the first embodiment of the present invention. In the ground fault detection method of the power system according to the embodiment of the present invention, the step S1 is executed through the steps S11 to S16:
s11, acquiring a clock signal of an external active crystal oscillator;
s12, performing primary clock frequency division on the clock signal, and taking the clock signal after the primary clock frequency division as a clock source of the real-time clock chip to generate a second-level time signal;
s13, carrying out secondary clock frequency division on the clock signal subjected to the primary clock frequency division to obtain a 1Hz clock signal;
s14, calibrating the 1Hz clock signal by using the GPS second pulse clock signal acquired by the GPS time service module to obtain a calibrated 1Hz clock signal;
s15, counting the calibrated 1Hz clock signal to generate a sub-second time signal;
and S16, obtaining the high-precision time stamp according to the second-level time signal and the sub-second-level time signal.
Specifically, referring to fig. 3, a flowchart of step S1 in a preferred implementation manner in the first embodiment of the present invention is shown. In the embodiment of the invention, the microcontroller is an STM32L4+ chip, and takes a clock signal of an external active crystal oscillator as the input of a high-speed external clock HSE of the microcontroller; wherein the HSE adopts a by-pass mode. The TIM of the internal timer of the microcontroller performs clock frequency division on the clock signal, and the frequency-divided clock signal is used as the input of a low-speed external clock LSE; wherein LSE adopts a by-pass mode; the LSE takes the clock signal after frequency division as a clock source of the RTC to generate a second-level time signal, namely a year, month, day, hour, minute and second signal; and selecting the clock source of the LPTIM as LSE, and carrying out clock frequency division on the clock signal again to generate a 1Hz clock signal.
And then, calibrating the 1Hz clock signal by using the GPS second pulse clock signal acquired by the GPS time service module to obtain the calibrated 1Hz clock signal. Specifically, the currently acquired GPS second pulse clock signal is used for reading and recording a 1Hz clock signal generated by an internal low power consumption counter LPTIM of the microcontroller, a count value is read when the GPS second pulse clock signal is acquired next time, the count value is compared with a theoretical calculation value, the frequency error of the current 1Hz clock signal is obtained, and whether the 1Hz clock signal is accurate or not is judged. If the frequency difference is not accurate, adjusting the frequency division factor according to the current frequency error, carrying out clock frequency division on the clock signal of the external active crystal oscillator again to obtain a new 1Hz clock signal, judging whether the new 1Hz clock signal is accurate by using the GPS second pulse clock signal again, and repeating iteration until the 1Hz clock signal is accurate to obtain the calibrated 1Hz clock signal.
And finally, counting the calibrated 1Hz clock signal by an internal counter TIM, wherein the output of the counter is the sub-second time. And combining the second-level time signal and the sub-second-level time signal to obtain the high-precision time stamp.
By adopting the technical means of the embodiment of the invention, the internal clock signal of the microcontroller is calibrated through the GPS second pulse clock signal acquired by the GPS time service module, so that the high-precision time service with the GPS time service system is realized, and the time service precision is less than 10 microseconds, thereby obtaining the high-precision timestamp. The high-precision time synchronization can be realized by the sensors arranged at other positions, the high-precision fault time timestamp is transmitted to the background and data is summoned and tested, the high-precision fault time timestamp can be obtained in the process of detecting the fault occurrence time of the power system, and the difficulty of subsequent fault positioning is reduced.
Further, in an implementation manner, referring to fig. 4, a flowchart of step S3 in an implementation manner in the first embodiment of the present invention is shown. Step S3 of the embodiment of the present invention is executed by steps S311 to S313:
s311, calculating an absolute value of the fundamental wave amplitude effective value of the zero sequence voltage data to serve as a zero sequence voltage amplitude index;
s312, judging whether the zero sequence voltage amplitude index exceeds a first preset threshold value and lasts for a first preset time;
s313, when the zero sequence voltage amplitude index exceeds a first preset threshold value and lasts for a first preset duration, judging that the power system has a ground fault.
In the embodiment of the invention, the absolute value of the effective value of the fundamental wave amplitude of the currently acquired zero-sequence voltage data is calculated to serve as the zero-sequence voltage amplitude index, so as to judge whether the power system has the ground fault. Preferably, the first preset threshold is set to 20V, and the first preset duration is set to 5 s. And when the current zero sequence voltage amplitude index obtained through calculation exceeds 20V and lasts for more than 5s, judging that the power system has the ground fault.
It can be understood that setting the first preset threshold to 20V and setting the first preset time period to 5s are only a preferred implementation manner in the embodiment of the present invention, and in practical applications, the first preset threshold and the first preset time period may also be adjusted according to the actual operating condition of the power system, which does not affect the beneficial effects obtained by the present invention.
In another implementation, referring to fig. 5, a flowchart of step S3 in another implementation manner in the first embodiment of the present invention is shown. Step S3 of the embodiment of the present invention is executed by steps S321 to S325:
s321, obtaining effective values of fundamental waves of previous N cycles of the current cycle of the zero-sequence voltage data as a first fundamental wave effective value set;
s322, obtaining an effective value of the fundamental wave of the (N + 1) th cycle of the current cycle of the zero sequence voltage data as a second fundamental wave effective value;
s323, according to the first fundamental wave effective value set and the second fundamental wave effective value, calculating a long-term voltage change index through the following calculation formula:
U＝|U1-U0|+|U2-U0|+(...)+|UN-U0|；
wherein, U1、U2...UNFor the first set of fundamental valid values, U0The second fundamental wave effective value is N is more than or equal to 1;
s324, judging whether the long-term voltage change index exceeds a second preset threshold value;
and S325, when the long-term voltage change index exceeds a second preset threshold value, judging that the power system has a ground fault.
In the embodiment of the invention, the effective value (50Hz power frequency quantity) U of the fundamental wave of continuous N cycles is used1、U2...UNSubtracting the effective value U of the fundamental wave of the first cycle before N cycles0And sequentially accumulating the absolute values to obtain the long-term voltage change index U, and judging whether the power system has a ground fault. And when the long-term voltage change index U exceeds a second preset threshold value, judging that the power system has a ground fault. Preferably, N is 64, and the second preset threshold is 60V.
For example, the effective value of 64 consecutive cycles is denoted as U1,U2…U64. The effective value of the cycle of the 64 continuous cycles is denoted as U0。
The long-term voltage variation index is: u ═ U1-U0|+|U2-U0|+(...)+|U64-U0|。
And judging whether U is greater than 60V, and if so, judging that the power system has a ground fault.
It can be understood that taking the value of N as 64 and setting the second preset threshold as 60V is only a preferred implementation manner in the embodiment of the present invention, and in practical application, the value of N and the first preset threshold may also be adjusted according to the actual operation condition of the power system, which does not affect the beneficial effects obtained by the present invention.
Further, when it is determined that the ground fault occurs in the power system, it is necessary to further obtain a high-precision fault occurrence time of the power system according to the high-precision timestamp. Referring to fig. 6, it is a flowchart illustrating step S4 of the ground fault detection method of the power system according to the embodiment of the present invention. Step S4 in the embodiment of the present invention is executed by steps S41 to S43:
s41, calculating each voltage sampling point x in the current cycle of the zero sequence voltage dataiVoltage sampling point y corresponding to the last cycleiAs voltage sampling point increments;
s42, calculating the time-dependent mutation index according to the voltage sampling point increment by the following calculation formula:
wherein, Δ xiThe increment of the voltage sampling points is adopted, and M is the number of the voltage sampling points in the cycle;
s43, when the time-varying index is judged to exceed a third preset threshold value and the absolute values of voltage sampling point increments of continuous preset number all exceed a fourth preset threshold value for the first time, determining the voltage sampling point x of the first voltage sampling point increment in the voltage sampling point increments of the preset numberiThe sampling time of (1) is the time of occurrence of the fault.
In the embodiment of the invention, each voltage sampling point in the current cycle is subtracted from each corresponding voltage sampling point in the previous cycle, and the absolute value of the effective value of the cycle data increment is calculated according to the increment of the voltage sampling point obtained after subtraction and is used as a time-varying index for determining the fault occurrence time of the power system.
As a preferred embodiment, the third preset threshold is set to 10V, the fourth preset threshold is set to 10V, and the preset number is set to 5. By way of example, assume that the number of samples per cycle is 256, i.e., for a 50Hz line frequency signal, the sampling frequency is 12.8 KHz. The 256 sampling points of the current cycle are marked as x1,x2,…x256256 samples of the previous wave are denoted as y1,y2,…y256，
The calculated value of the temporal mutation index is
Assume a voltage sample point increment of Δ x1,Δx2,…Δx256，Δxi＝xi-yiAnd if the value of the temporal mutation index exceeds a third preset threshold value of 10V, sequentially detecting | Δ x ═ 1,2, … 2561|,|Δx2|,…|Δx256If the absolute value of five consecutive variables exceeds a fourth preset threshold value 10V, for example, | Δ x50|,|Δx51|,…|Δx54If so, determine | Δ x50Voltage sampling point x corresponding to |50The sampling time of the time synchronization module is the fault occurrence time, and the high-precision fault occurrence time of the power system can be obtained according to the high-precision time stamp because the microcontroller is subjected to high-precision time synchronization with the GPS time service system.
It can be understood that setting the third preset threshold to 10V, setting the fourth preset threshold to 10V, and setting the preset number to 5 are only one preferred implementation manner in the embodiment of the present invention, and in practical applications, the third preset threshold, the fourth preset threshold, and the preset number may also be adjusted according to the actual operating condition of the power system, which does not affect the beneficial effects obtained by the present invention.
By adopting the technical means of the embodiment of the invention, after the microcontroller receives the zero sequence voltage data, the zero sequence voltage amplitude index, the long-term voltage change index and the time mutation index are calculated according to the zero sequence voltage data, when the zero sequence voltage amplitude index or the long-term voltage change index meets the corresponding threshold value condition, the occurrence of the ground fault of the power system is judged, and the occurrence time of the fault of the power system is analyzed and obtained according to the time mutation index. In addition, the microcontroller and the GPS time service system are subjected to high-precision time synchronization, so that a high-precision fault occurrence time stamp is obtained, the difficulty of subsequent fault positioning is favorably reduced,
as a preferred implementation manner, the method for detecting a ground fault of an electric power system according to an embodiment of the present invention further includes step S5:
and S5, after the fault occurrence time of the power system is obtained, sending the fault occurrence time of the power system to a communication module so that the communication module reports the fault occurrence time of the power system to a background.
In an embodiment of the invention, the communication module is connected with the microcontroller. And after the microcontroller analyzes and obtains the fault occurrence time of the power system, the fault occurrence time is sent to the communication module, and the communication module reports the information that the power system has faults and the fault occurrence time to a background.
Preferably, the communication module is a 4G communication module, and when the 4G communication module receives information that a ground fault has occurred in the power system and a fault occurrence time, the information is uploaded to a background. As the distance, the format of the uploaded information at the time of the occurrence of the failure is shown in table 1:
table 1 upload information format at the time of occurrence of failure
By adopting the technical means of the embodiment of the invention, the information of the occurrence of the ground fault and the occurrence time of the fault of the power system can be timely uploaded to the background, so that the background system can conveniently arrange workers to timely and accurately troubleshoot and solve the fault of the power system, and the safe and stable operation of the power system is improved.
Fig. 7 is a schematic structural diagram of a ground fault detection apparatus of an electric power system according to a second embodiment of the present invention. The embodiment of the invention provides a ground fault detection device 20 of an electric power system, which comprises a microcontroller 21, a GPS time service module 22 and a zero sequence voltage acquisition module 23; the microcontroller 21 is connected to the GPS time service module 22 and the zero sequence voltage acquisition module 23 respectively; the microprocessor 21 performs the ground fault detection method of the power system according to the first embodiment.
In the embodiment of the present invention, referring to fig. 8, a schematic circuit structure diagram of a GPS time service module in the embodiment of the present invention is shown. The GPS time service module 22 is configured to acquire a pulse-per-second clock signal of the GPS time service system, so that the microcontroller 21 realizes high-precision time synchronization with the GPS time service system, thereby obtaining a high-precision timestamp, which is beneficial to obtaining a high-precision fault occurrence time timestamp in a process of detecting a fault occurrence time of an electric power system, and reducing difficulty in subsequent fault location.
Further, the zero sequence voltage acquisition module 23 includes an ADC chip, which is in a master mode, connected to the microcontroller 21 through a serial peripheral interface SPI, and stores zero sequence voltage data in a DMA mode. The zero sequence voltage data are collected in a sine wave mode, the collection frequency is 12.8KHz, namely 12.8K data are collected in one second, and each data is 2 bytes. One sine wave is 20ms and one wave takes 256 data, occupying 512 bytes.
It should be noted that, the microcontroller in the ground fault detection apparatus 20 of the power system according to the embodiment of the present invention is configured to execute all the process steps of the ground fault detection method of the power system according to the above embodiment, and the working principles and beneficial effects of the two are in one-to-one correspondence, and thus are not described again.
As a preferred embodiment, referring to fig. 7, the ground fault detection device 20 of the power system further comprises a communication module 24; the communication module 24 is connected with the microcontroller 21;
the communication module 24 is configured to receive the fault occurrence time of the power system sent to the controller after obtaining the fault occurrence time of the power system, and report the fault occurrence time of the power system to a background.
Fig. 9 is a schematic circuit diagram of a communication module according to an embodiment of the present invention. The communication module is a 4G communication module. When the microcontroller analyzes and obtains the fault occurrence time of the power system, the fault occurrence time is sent to the communication module, and the communication module reports the information of the fault occurrence time and the fault occurrence time of the power system to the background, so that the background system can conveniently arrange workers to timely and accurately troubleshoot and solve the fault occurrence of the power system, and the safe and stable operation of the power system is improved.
The 4G communication module with the microcontroller uses USART3 to communicate, can pass through the PG4 pin control of microcontroller the RESIN _ N pin level of 4G communication module realizes the hardware of 4G communication module resets, and when PG4 pin level is low, RESIN _ N pin level is high, 4G communication module normally works. When the PG4 pin level is high (the high level duration is 50ms-100ms), the RESIN _ N pin level is low, and the 4G communication module hardware is reset. The RESIN _ N pin does not need a pull-up resistor, and because the RESIN _ N signal is sensitive, a capacitor C21 needs to be introduced for filtering.
Preferably, the communication module 24 is further configured to report heartbeat information of the device itself in real time during a working process of the ground fault detection device 20 of the power system, so that a background can detect whether the ground fault detection device 20 is in a normal working state in real time. The communication module 24 sends heartbeat packets to the background at regular time, and the information format is shown in table 2:
table 2 heartbeat information reporting format of device
As a preferred embodiment, referring to fig. 7, the ground fault detection apparatus 20 of the power system further includes a power module 25, and the power module 25 is respectively connected to the microcontroller 21, the zero sequence voltage acquisition module 23, and the communication module 24. The power circuit 25 is used for supplying power to the microcontroller, the zero sequence voltage acquisition module and the communication module.
Specifically, referring to fig. 10, a schematic diagram of a circuit structure of the power module in the embodiment of the present invention is shown. Referring to fig. 10a, the power module 25 converts the 12V voltage into 3.3V to supply power to the microcontroller 21; referring to fig. 10b, the power module 25 converts the 12V voltage into 3.8V to supply power to the 4G communication module 24; referring to fig. 10c, the power module 25 converts the 12V voltage into 5V, and supplies power to the zero sequence voltage acquisition module 22. And supplying power to each circuit module in the ground fault detection device 20 of the power system through the power supply module, thereby ensuring the normal operation of the ground fault detection device 20 of the power system.
As a preferred embodiment, referring to fig. 7, the ground fault detection device 20 of the power system further comprises a data storage module 26; the data storage module 26 is connected to the microcontroller. The data storage module 26 is configured to store data information that needs to be stored during operation of the ground fault detection apparatus of the power system, including but not limited to the zero sequence voltage data, information that the power system has a fault, and a time when the fault of the power system occurs.
The second embodiment of the invention provides a ground fault detection device of an electric power system, which comprises a microcontroller, a GPS time service module, a zero sequence voltage acquisition module, a communication module, a power supply module and a data storage module. And the microcontroller receives the GPS second pulse clock signal acquired by the GPS time service module and calibrates the internal clock signal to obtain the high-precision timestamp. Meanwhile, the microcontroller receives the zero sequence voltage data of the power system acquired by the zero sequence voltage acquisition module in real time; judging whether the power system has a ground fault according to the zero sequence voltage data; and when the power system has a ground fault, obtaining the fault occurrence time of the power system according to the zero sequence voltage data and the high-precision timestamp. By acquiring the accurate fault occurrence time, the difficulty of fault point positioning can be greatly reduced in the process of fault point positioning, the fault occurring in the power system can be timely and accurately checked and solved, and the safe and stable operation of the power system is improved.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.
Claims (10)
1. A ground fault detection method of an electric power system, characterized by being executed by a microcontroller, the ground fault detection method of an electric power system comprising:
receiving a GPS second pulse clock signal acquired by a GPS time service module, and calibrating an internal clock signal by using the GPS second pulse clock signal to obtain a high-precision timestamp;
receiving zero sequence voltage data of the power system acquired by the zero sequence voltage acquisition module in real time;
judging whether the power system has a ground fault according to the zero sequence voltage data;
and when the power system has a ground fault, obtaining the fault occurrence time of the power system according to the zero sequence voltage data and the high-precision timestamp.
2. The method for detecting a ground fault of an electric power system according to claim 1, wherein the receiving the GPS second pulse clock signal acquired by the GPS time service module and calibrating the internal clock signal by using the GPS second pulse clock signal to obtain the high-precision timestamp specifically comprises:
acquiring a clock signal of an external active crystal oscillator;
performing primary clock frequency division on the clock signal, and taking the clock signal subjected to the primary clock frequency division as a clock source of a real-time clock chip to generate a second-level time signal;
carrying out secondary clock frequency division on the clock signal subjected to the primary clock frequency division to obtain a 1Hz clock signal;
calibrating the 1Hz clock signal by using the GPS second pulse clock signal acquired by the GPS time service module to obtain a calibrated 1Hz clock signal;
counting the calibrated 1Hz clock signal to generate a sub-second time signal;
and obtaining the high-precision timestamp according to the second-level time signal and the sub-second-level time signal.
3. The method according to claim 1, wherein the determining whether the power system has a ground fault according to the zero-sequence voltage data specifically includes:
calculating an absolute value of the effective value of the fundamental wave amplitude of the zero sequence voltage data to be used as a zero sequence voltage amplitude index;
judging whether the zero sequence voltage amplitude index exceeds a first preset threshold value and lasts for a first preset time;
and when the zero sequence voltage amplitude index exceeds a first preset threshold value and lasts for a first preset duration, judging that the power system has a ground fault.
4. The method according to claim 1, wherein the determining whether the power system has a ground fault according to the zero-sequence voltage data specifically includes:
obtaining effective values of fundamental waves of N previous cycles of the current cycle of the zero-sequence voltage data as a first fundamental wave effective value set;
obtaining an effective value of a fundamental wave of the (N + 1) th cycle of the current cycle of the zero-sequence voltage data as a second fundamental wave effective value;
according to the first fundamental wave effective value set and the second fundamental wave effective value, calculating a long-term voltage change index through the following calculation formula:
U＝|U1-U0|+|U2-U0|+(...)+|UN-U0|；
wherein, U1、U2...UNFor the first set of fundamental valid values, U0The second fundamental wave effective value is N is more than or equal to 1;
judging whether the long-term voltage change index exceeds a second preset threshold value or not;
and when the long-term voltage change index exceeds a second preset threshold value, judging that the power system has a ground fault.
5. The method according to claim 1, wherein obtaining the fault occurrence time of the power system according to the zero-sequence voltage data and the high-precision timestamp when the power system has a ground fault specifically includes:
calculating each voltage sampling point x in the current cycle of the zero sequence voltage dataiVoltage sampling point y corresponding to the last cycleiAs voltage sampling point increments;
according to the voltage sampling point increment, calculating a time mutation index by the following calculation formula:
wherein, Δ xiThe increment of the voltage sampling points is adopted, and M is the number of the voltage sampling points in the cycle;
when the time-varying index is judged to exceed a third preset threshold value and the absolute values of the voltage sampling point increments with continuous preset number exceed a fourth preset threshold value for the first time, determining the voltage sampling point x of the first voltage sampling point increment in the voltage sampling point increments with preset numberiThe sampling time of (1) is the time of occurrence of the fault.
6. The ground fault detection method of an electric power system according to claim 1, characterized in that the ground fault detection method of an electric power system further comprises:
after the fault occurrence time of the power system is obtained, the fault occurrence time of the power system is sent to a communication module, so that the communication module reports the fault occurrence time of the power system to a background.
7. The ground fault detection device of the power system is characterized by comprising a microcontroller, a GPS time service module and a zero sequence voltage acquisition module; the microcontroller is respectively connected with the GPS time service module and the zero sequence voltage acquisition module; the microprocessor executes the ground fault detection method of the power system according to any one of claims 1 to 5.
8. The ground fault detection device of an electric power system according to claim 7, wherein the ground fault detection device of an electric power system further comprises a communication module; the communication module is connected with the microcontroller;
the communication module is used for receiving the fault occurrence time of the power system sent by the controller after obtaining the fault occurrence time of the power system, and reporting the fault occurrence time of the power system to a background.
9. The ground fault detection device of claim 8, further comprising a power supply module, wherein the power supply circuit is connected to the microcontroller, the zero sequence voltage acquisition module and the communication module respectively;
the power circuit is used for supplying power to the microcontroller, the zero sequence voltage acquisition module and the communication module.
10. The ground fault detection device of an electric power system according to claim 7, wherein the ground fault detection device of an electric power system further comprises a data storage module; the data storage module is connected with the microcontroller.
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