CN115267415B - Method for discriminating single-phase earth fault of stock distribution network and terminal thereof - Google Patents
Method for discriminating single-phase earth fault of stock distribution network and terminal thereof Download PDFInfo
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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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- G—PHYSICS
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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
- G01R31/50—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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- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
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Abstract
The invention discloses a method for distinguishing single-phase earth faults of an inventory distribution network and a terminal thereof, wherein the terminal comprises a current acquisition unit and a fault detection indication unit; the current acquisition unit is used for acquiring three-phase current signals of the stock distribution network terminal; the fault detection and indication unit is used for realizing detection, communication and indication of single-phase grounding faults according to the collected three-phase current signals of the stock distribution network terminal; the method comprises the following steps: collecting three-phase current signals of an inventory distribution network terminal; extracting fault characteristics of the three-phase temporary steady-state current signals; based on the extracted fault characteristics, the on-site judgment of the single-phase ground fault of the distribution network is realized. The invention overcomes the dependence of the traditional distribution network fault diagnosis on zero sequence voltage under the condition of not adding the zero sequence voltage transformer, realizes the on-site discrimination of the distribution network single-phase grounding fault, and solves the problem that the existing stock distribution network terminal equipment cannot effectively solve the long-term fault positioning problem of the distribution network in a low-cost, high-reliability, flexible and convenient mode.
Description
Technical Field
The invention belongs to the technical field of distribution network protection, and particularly relates to a single-phase grounding fault distinguishing method and a terminal of an inventory distribution network.
Background
With the continuous development of urban power grids along with construction, in recent years, the problem of single-phase earth fault disposal of urban power distribution cable networks is increasingly prominent due to the occurrence of events of fire of cable channels caused by single-phase earth faults. The traditional way of selecting the line through manual way pulling is time-consuming and labor-consuming, and the insulation breakdown of old cables or switching equipment can be caused by overvoltage caused by operation with faults, so that the accident range and the hazard degree are further enlarged, and the system safety and the power supply reliability are seriously influenced. Therefore, the rapid and accurate detection of the single-phase earth fault is of great significance for finding, removing and timely recovering power supply of the fault point, and has positive effects for guaranteeing safe and stable and economical operation of the whole power system.
In China, the neutral point grounding mode of the distribution network is mainly grounding or non-grounding through an arc suppression coil, and the grounding mode generally belongs to a small-current grounding system and has the measuring characteristics of small fault current, complex electromagnetic environment of a measuring environment, unstable grounding arc and extremely short transient signal duration. At present, the distribution line side generally detects the fault through distribution terminals such as a distribution automation system or a fault indicator, but the fault is detected effectively due to the problems of small fault signal, low sampling rate, poor precision, imperfect and communication of the existing research and judgment algorithm, so that the sensitivity is not high, and the effective detection of the fault cannot be realized generally.
In addition, the urban areas with dense population and relatively high reliability of distribution network structures are generally grounded by adopting a neutral point grounding mode, the grounding mode generally belongs to a high-current grounding system, but when a high-resistance grounding fault occurs, the generated fault current is still small, according to the existing setting method of zero-sequence overcurrent protection, when the equivalent resistance value of the grounding transition resistance exceeds 100 omega, the zero-sequence overcurrent protection cannot effectively detect single-phase grounding faults, so that discrimination of single-phase grounding faults is realized through zero-sequence voltage and zero-sequence current, but for distribution lines, a zero-sequence voltage transformer is not configured due to the consideration of ferromagnetic resonance and other reasons, and therefore, the existing mature detection device cannot be applied to line side to realize single-phase grounding fault positioning.
Disclosure of Invention
The invention aims to: in order to overcome the dependence of the stock distribution network single-phase earth fault detection on zero sequence voltage, the stock distribution network single-phase earth fault judging method and the terminal thereof are provided by considering that the stock distribution network does not have zero sequence voltage and zero sequence current acquisition conditions, so that the on-site judgment of the distribution network single-phase earth fault can be realized, zero sequence voltage signals are not required to be acquired, the ferromagnetic resonance risk is avoided, and the dependence of the traditional distribution network fault diagnosis on the zero sequence voltage is overcome.
The technical scheme is as follows: in order to achieve the above purpose, the invention provides a method for discriminating single-phase earth faults of an inventory distribution network, comprising the following steps:
s1: collecting three-phase current signals of an inventory distribution network terminal;
s2: extracting fault characteristics of a three-phase temporary steady-state current signal:
s3: judging whether the transient phase directions of the three-phase currents are consistent according to the extracted fault characteristics, and calculating the dissymmetry of the steady-state interphase amplitude of the three-phase currents;
s4: based on the data of the step S3, the on-site judgment of the single-phase grounding fault of the distribution network is realized.
Further, the method for extracting the fault characteristics of the three-phase transient steady-state current signal in the step S2 includes:
the three-phase current signal is utilized to self-synthesize a zero-sequence current signal, the abrupt change value of the zero-sequence current variation is monitored to be larger than K, K is taken as a fixed value, 15-20 mA is generally taken, wavelet packet transformation is further carried out on the three-phase current and the self-synthesize zero-sequence current, and the asymmetry of the three-phase current acquisition signal phase and amplitude between phases in short time windows before and after a fault is extracted.
Further, the method for calculating the mutation value of the zero sequence current variation in the step S2 is as follows:
k 0 ＝i 0 (t)-i 0 (t-T)
wherein i is a 、i b 、i c The current collection amounts of the phase A, the phase B and the phase C are respectively; i.e 0 Is a self-synthesized zero sequence current value; k (k) 0 Is the abrupt change value of the zero sequence current variation; t is the power frequency period.
Further, the method for judging whether the transient phase directions of the three-phase currents in the step S3 are consistent is as follows:
judging the three-phase current transient phase direction according to whether the three-phase current mutation is larger than 0, if the three-phase current mutation values are larger than 0 or smaller than 0, judging that the directions are consistent, otherwise, judging that the directions are inconsistent.
Further, in the step S3, the three-phase current transient phase direction determination formula is:
wherein,the current abrupt change value of each phase A, B, C after the load current is filtered through wavelet packet transformation; t is t fault The time of occurrence of the fault is the time of occurrence of the fault; t is the power frequency period.
Further, in the step S3, a calculation formula of the phase-to-phase amplitude asymmetry of the three-phase current steady-state phase is as follows:
wherein i is ab 、i bc 、i ca Filtering the difference of AB, BC and CA phase currents after load current is filtered through wavelet packet transformation; t is t fault The time of occurrence of the fault is the time of occurrence of the fault; t is the power frequency period.
Further, the method for in-situ judging the single-phase ground fault of the distribution network in the step S4 is as follows:
a single-phase earth fault occurs downstream of the fault monitoring point, wherein the opposite phases are fault phases;
if the transient phase directions of the three-phase currents are inconsistent and the dissymmetry of the steady-state interphase amplitude values of the three-phase currents is smaller than X1, further expanding a calculation time window of the dissymmetry of the steady-state interphase amplitude values of the three-phase currents, and if the dissymmetry is larger than X2, judging that a single-phase earth fault occurs at the downstream of the monitoring point, wherein the phases are opposite;
if the transient phase directions of the three-phase currents are consistent, but the dissymmetry of the steady-state interphase amplitude of the three-phase currents is larger than X1, further judging that the dissymmetry is larger than X3, and if the conditions are met, judging that a single-phase grounding fault occurs at the downstream of the monitoring point, wherein the single-phase grounding fault occurs at the downstream of the monitoring pointThe phase not included in the phase sequence is a fault phase;
if the transient phase directions of the three-phase currents are consistent, but the dissymmetry of the steady-state interphase amplitude of the three-phase currents is smaller than X1, judging that a single-phase grounding fault does not occur at the downstream of the monitoring point.
The invention also provides a single-phase earth fault discrimination terminal of the stock distribution network, which comprises a current acquisition unit and a fault detection indication unit;
the current acquisition unit is used for acquiring three-phase current signals of the stock distribution network terminal;
the fault detection and indication unit is used for realizing detection, communication and indication of single-phase grounding faults according to the collected three-phase current signals of the stock distribution network terminal.
Further, the current collection unit collects three-phase current signals of the stock distribution network terminal through the open-close type current transformer, the open-close type current transformer is of a buckle type structure, one end of the open-close type current transformer is connected with the current collection unit, and the other end of the open-close type current transformer is connected with the secondary current collection terminal of the stock distribution network terminal through the buckle type structure.
Further, the fault detection indication unit comprises an adaptive power supply module, a data processing and algorithm processing module and a communication indication module;
the self-adaptive power supply module is used for providing a working power supply for the fault detection indication unit;
the data processing and algorithm processing module is used for realizing the detection of single-phase grounding faults;
the communication indicating module is used for communication between the distribution network single-phase ground fault judging terminal, the stock distribution network terminal and the distribution automation master station, and realizing functions of relevant remote signaling, remote measurement and the like, and detecting and positioning the distribution network single-phase ground fault.
Further, a clamping groove and a guide rail which are matched with each other are respectively arranged between the stock distribution network single-phase grounding fault distinguishing terminal and the stock distribution network terminal, and the stock distribution terminal is provided with the guide rail which is used for fixing the installed equipment.
The beneficial effects are that: compared with the prior art, the invention has the following advantages:
1. under the condition that a zero sequence voltage transformer is not additionally arranged, the open-close type current transformer is mainly adopted to collect three-phase current signals, the zero sequence voltage signals are not required to be collected, the ferromagnetic resonance risk is avoided, the dependence of the former distribution network fault diagnosis on zero sequence voltage is overcome, the fault characteristics of the three-phase temporary steady-state current signals are extracted by utilizing a wavelet packet transformation and other highly reliable algorithms, the on-site judgment of the distribution network single-phase grounding faults is realized, and the problem that the existing stock distribution network terminal equipment cannot effectively solve the long-term fault positioning problem of the distribution network is solved in a low-cost, highly reliable, flexible and convenient mode.
2. The invention adopts the open-close type current transformer with the clamping structure to collect three-phase current signals, and can collect the current signals only by clamping the open-close type current transformer on the existing protection or metering secondary current loop, thereby improving the safety of electrified work and reducing the power failure time to the greatest extent.
Drawings
FIG. 1 is a schematic diagram of the connection of a distribution network single-phase earth fault discrimination terminal and an inventory distribution network terminal;
fig. 2 is a schematic front view of a distribution network single-phase earth fault discrimination terminal;
FIG. 3 is a schematic side view of a distribution network single-phase earth fault discrimination terminal;
FIG. 4 is a schematic view of a card slot and guide rail;
FIG. 5 is a schematic diagram of an open-close current transformer;
FIG. 6 is a schematic diagram of the connection of an open-close current transformer;
FIG. 7 is a schematic diagram of the wiring of the open-close current transformer;
fig. 8 is an internal schematic diagram of an inventory distribution network terminal;
FIG. 9 is k 0 Is a schematic diagram of the variation of (a).
Detailed Description
The present invention is further illustrated in the accompanying drawings and detailed description which are to be understood as being merely illustrative of the invention and not limiting of its scope, and various modifications of the invention, which are equivalent to those skilled in the art upon reading the invention, will fall within the scope of the invention as defined in the appended claims.
As shown in FIG. 1, the invention provides a single-phase earth fault discrimination terminal of an inventory distribution network, which comprises a current acquisition unit and a fault detection indication unit;
the current acquisition unit is used for acquiring three-phase current signals of the stock distribution network terminal;
the fault detection and indication unit is used for realizing detection, communication and indication of single-phase grounding faults according to the collected three-phase current signals of the stock distribution network terminal.
The fault detection indication unit comprises an adaptive power supply module, a data processing and algorithm processing module and a communication indication module;
the self-adaptive power supply module is used for providing a working power supply for the fault detection indication unit and can receive 24-65V direct current power supply from the outside;
the data processing and algorithm processing module is used for realizing the detection of single-phase grounding faults;
the communication indicating module is used for communication between the distribution network single-phase ground fault judging terminal and the stock distribution network terminal as well as between the distribution network single-phase ground fault judging terminal and the distribution automation master station, and realizing functions of relevant remote signaling, remote measurement and the like, and realizing detection and positioning of the distribution network single-phase ground fault.
As shown in fig. 2 and fig. 3, the distribution network single-phase grounding fault discrimination terminal specifically comprises a shell, wherein a front panel of the shell is embedded with a status indicator lamp, and the indicator lamp is respectively operated, warned and grounded; the upper end of the shell is embedded with a working power interface area, an alternating current analog quantity signal acquisition area and a standby interface area, wherein the working power interface area comprises a shell ground and a DC 24V power supply; the lower end of the shell is embedded with a switching value output interface area, a communication interface area and a standby interface area, wherein the communication interface area consists of a serial port and an Ethernet port; the rear end panel of the shell is provided with a clamping groove for clamping a standard guide rail of the DTU or the FTU; the upper end of the shell is sequentially provided with a working power interface area, a standby interface area and an alternating current analog quantity signal acquisition area from left to right; the lower end of the shell is provided with a network port communication interface area, a switching value output interface area, a standby interface area and a serial port communication interface area in sequence from left to right.
Four types of input/output ports are arranged outside the fault detection indication unit: the first type of input/output ports are connected with the current acquisition unit, the second type of input/output ports are connected with the direct-current power supply unit of the stock distribution terminal, the third type of input/output ports are connected with the standby switch-in unit of the stock distribution terminal, and the fourth type of input/output ports are connected with the wired/wireless communication unit of the stock distribution terminal. The size of the fault detection indication unit shell can be matched with the standardized power distribution terminals such as FTU and DTU, DIN buckles are arranged outside the shell, and the fault detection indication unit shell can be fixed on DIN guide rails of the stock power distribution terminals.
The hardware system architecture adopts a plugboard bus structure and mainly comprises a CPU module, an AC module, a TRIP module, a power module and a communication module, can realize a single-phase grounding fault detection function of 1 outlet interval, and supports Ethernet communication and RS232/485 communication. The core CPU module adopts a low-power digital signal processor ARM as a main processor, and is interacted with the AC module to complete current alternating current sampling processing calculation and fault judgment, and is interacted with the TRIP module and the communication module to realize the communication between the power distribution terminal and a power distribution automation master station, thereby completing the realization of functions such as related remote signaling, remote measurement and the like. The AC module completes the collection of alternating current signals, a high-speed 16bit and 4 channel synchronous sampling A/D converter is adopted, and the chip integrates an analog power supply, so that on one hand, the system design can be simplified, and on the other hand, the hardware cost of an analog channel can be greatly reduced. After the AD module completes synchronous sampling, the sampling value is transmitted to the CPU for processing through the high-speed bus AHB by filtering. The TRIP module is provided with a 2-way switching value output interface, and can remotely control a 1-way protection opening outlet and a 1-way device running state outlet. The power module provides 24V dc operating power. The communication module provides 1 serial port and 1 network port and is responsible for providing communication functions for the terminal.
Referring to fig. 4, a guide rail matched with a card slot of a single-phase earth fault discrimination terminal of the stock distribution network is provided on the stock distribution network terminal, and in the single-phase earth fault detection, the single-phase earth fault discrimination terminal of the stock distribution network can be mounted on the stock distribution network terminal through the card slot and the guide rail.
As shown in fig. 5-7, the current collection unit collects three-phase current signals of the stock distribution network terminal through an open-close current transformer (ct), the open-close current transformer is of a buckle structure, one end of the open-close current transformer is connected with the current collection unit, and the other end of the open-close current transformer is connected with the secondary current collection terminal of the stock distribution network terminal through the buckle structure.
As shown in fig. 8, for the engineering of modifying the stock power distribution terminal, the installation mode of the device is flexible, and the device is adapted to the stock FTU/DTU guide rail, and can be dispersedly buckled in the cabinet body according to the cabinet body space, as shown in fig. 3. Engineering debugging can be realized remotely through a power distribution automation master station, the device supports various communication protocols such as IEC60870-5-101, IEC60870-5-104 and the like, various media configuration basic information such as Ethernet ports, serial ports, 4G/5G private network communication and the like can be realized through matched communication servers, and unified debugging of the power distribution automation master station can be realized through remote calling of sampling information, fault SOE, wave recording information and the like.
Based on the above scheme, the embodiment uses the single-phase ground fault discrimination terminal of the stock distribution network to detect single-phase ground faults of the stock DTU, and provides a single-phase ground fault discrimination method of the stock distribution network, which comprises the following steps:
s1: collecting three-phase current signals of the stock DTU:
the current acquisition unit of the buckle type CT and distribution network single-phase grounding fault judging device jointly realizes synchronous acquisition of three-phase current;
s2: extracting fault characteristics of a three-phase temporary steady-state current signal:
the three-phase current signal is utilized to self-synthesize a zero-sequence current signal, the abrupt change value of the zero-sequence current variation is monitored to be larger than K, K is a fixed value, in the embodiment, 0.02A is selected, wavelet packet transformation is further carried out on the three-phase current and the self-synthesize zero-sequence current, and the asymmetry of the phase and the amplitude between the phases of the three-phase current acquisition signals in a short time window before and after a fault is extracted.
In this embodiment, the short window has a value range (-T, T), t=0.02 s.
The method for calculating the abrupt change value of the zero sequence current variation comprises the following steps:
k 0 ＝i 0 (t)-i 0 (t-T)
wherein i is a 、i b 、i c The current collection amounts of the phase A, the phase B and the phase C are respectively; i.e 0 Is a self-synthesized zero sequence current value; k (k) 0 Is the abrupt change value of the zero sequence current variation; t is the power frequency period.
S3: judging whether the transient phase directions of the three-phase currents are consistent according to the extracted fault characteristics, and calculating the dissymmetry of the steady-state interphase amplitude of the three-phase currents:
the method for judging whether the transient phase directions of the three-phase currents are consistent in the embodiment is as follows:
judging the three-phase current transient phase direction according to whether the three-phase current mutation is larger than 0, if the three-phase current mutation values are larger than 0 or smaller than 0, judging that the directions are consistent, otherwise, judging that the directions are inconsistent.
The three-phase current transient phase direction judging formula is as follows:
wherein,the current abrupt change value of each phase A, B, C after the load current is filtered through wavelet packet transformation; t is t fault The time of occurrence of the fault is the time of occurrence of the fault; t is the power frequency period.
The calculation formula of the three-phase current steady-state interphase amplitude asymmetry is as follows:
wherein i is ab 、i bc 、i ca Filtering the difference of AB, BC and CA phase currents after load current is filtered through wavelet packet transformation; t is t fault The time of occurrence of the fault is the time of occurrence of the fault; t is the power frequency period.
S4: based on the data in the step S3, the on-site judgment of the single-phase grounding fault of the distribution network is realized:
if the transient phase directions of the three-phase currents are inconsistent and the dissymmetry of the steady-state interphase amplitude of the three-phase currents is larger than X1, judging that a single-phase grounding fault occurs at the downstream of the monitoring point, wherein the phases are opposite;
if the transient phase directions of the three-phase currents are inconsistent and the dissymmetry of the steady-state interphase amplitude values of the three-phase currents is smaller than X1, further expanding a calculation time window of the dissymmetry of the steady-state interphase amplitude values of the three-phase currents, and if the dissymmetry is larger than X2, judging that a single-phase earth fault occurs at the downstream of the monitoring point, wherein the phases are opposite;
if the transient phase directions of the three-phase currents are consistent, but the dissymmetry of the steady-state interphase amplitude of the three-phase currents is larger than X1, further judging that the dissymmetry is larger than X3, and if the conditions are met, judging that a single-phase grounding fault occurs at the downstream of the monitoring point, wherein the single-phase grounding fault occurs at the downstream of the monitoring pointThe phase not included in the phase sequence is a fault phase;
if the transient phase directions of the three-phase currents are consistent, but the dissymmetry of the steady-state interphase amplitude of the three-phase currents is smaller than X1, judging that a single-phase grounding fault does not occur at the downstream of the monitoring point.
In this example, X1 is 5 to 7, X2 is 3 to 5, and X3 is 7 to 10.
Based on the above scheme, in order to verify the effectiveness of the method of the present invention, the following examples are performed:
taking a system occurrence A phase ground fault as an example, filtering and calculating the mutation value of the zero sequence current variation in S2, and k 0 The change in (c) is shown in fig. 9, where the Y point is the time when the amount of mutation is greater than the setting value 0.02A, at which time the fault determination logic is activated.
And (3) calculating the transient phase direction and the steady-state asymmetry of the three-phase current according to the formula in the step (S3), wherein the results are shown in the following table, the transient phase direction of the three-phase current is inconsistent, and the steady-state interphase amplitude asymmetry of the three-phase current is greater than X1, so that the single-phase earth fault downstream of the monitoring point is judged.
The embodiment also provides a single-phase earth fault discrimination system of the stock distribution network, which comprises a network interface, a memory and a processor; the network interface is used for receiving and transmitting signals in the process of receiving and transmitting information with other external network elements; a memory storing computer program instructions executable on the processor; and a processor for executing the steps of the consensus method as described above when executing the computer program instructions.
The present embodiment also provides a computer storage medium storing a computer program which, when executed by a processor, implements the method described above. The computer-readable medium may be considered tangible and non-transitory. Non-limiting examples of non-transitory tangible computer readable media include non-volatile memory circuits (e.g., flash memory circuits, erasable programmable read-only memory circuits, or masked read-only memory circuits), volatile memory circuits (e.g., static random access memory circuits or dynamic random access memory circuits), magnetic storage media (e.g., analog or digital magnetic tape or hard disk drives), and optical storage media (e.g., CDs, DVDs, or blu-ray discs), among others. The computer program includes processor-executable instructions stored on at least one non-transitory tangible computer-readable medium. The computer program may also include or be dependent on stored data. The computer programs may include a basic input/output system (BIOS) that interacts with the hardware of the special purpose computer, device drivers that interact with particular devices of the special purpose computer, one or more operating systems, user applications, background services, background applications, and so forth.
It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Claims (2)
1. The method for distinguishing the single-phase earth fault of the stock distribution network is characterized by comprising the following steps of:
s1: collecting three-phase current signals of an inventory distribution network terminal;
s2: extracting fault characteristics of a three-phase temporary steady-state current signal:
s3: judging whether the transient phase directions of the three-phase currents are consistent according to the extracted fault characteristics, and calculating the dissymmetry of the steady-state interphase amplitude of the three-phase currents;
s4: based on the data of the step S3, the on-site judgment of the single-phase grounding fault of the distribution network is realized;
the method for extracting the fault characteristics of the three-phase transient steady-state current signal in the step S2 comprises the following steps:
the three-phase current signal is utilized to self-synthesize a zero-sequence current signal, wavelet packet transformation is further carried out on the three-phase current and the self-synthesize zero-sequence current by monitoring that the mutation value of the zero-sequence current variation is larger than K, and the asymmetry of the phase and the amplitude between the phases of the three-phase current acquisition signals in short time windows before and after the fault is extracted;
the method for calculating the abrupt change value of the zero sequence current variation in the step S2 comprises the following steps:
k 0 ＝i 0 (t)-i 0 (t-T)
wherein i is a 、i b 、i c The current collection amounts of the phase A, the phase B and the phase C are respectively; i.e 0 Is a self-synthesized zero sequence current value; k (k) 0 Is the abrupt change value of the zero sequence current variation; t is a power frequency period;
in the step S3, the three-phase current transient phase direction judgment formula is as follows:
wherein,the current abrupt change value of each phase A, B, C after the load current is filtered through wavelet packet transformation; t is t fault The time of occurrence of the fault is the time of occurrence of the fault; t is a power frequency period;
the calculation formula of the three-phase current steady-state interphase amplitude asymmetry in the step S3 is as follows:
wherein i is ab 、i bc 、i ca Filtering the difference of AB, BC and CA phase currents after load current is filtered through wavelet packet transformation; t is t fault The time of occurrence of the fault is the time of occurrence of the fault; t is the power frequency period；
The method for judging the single-phase grounding fault of the distribution network in situ in the step S4 comprises the following steps:
if the transient phase directions of the three-phase currents are inconsistent and the dissymmetry of the steady-state interphase amplitude of the three-phase currents is larger than X1, judging that a single-phase grounding fault occurs at the downstream of the monitoring point, wherein the phases are opposite;
if the transient phase directions of the three-phase currents are inconsistent and the dissymmetry of the steady-state interphase amplitude values of the three-phase currents is smaller than X1, further expanding a calculation time window of the dissymmetry of the steady-state interphase amplitude values of the three-phase currents, and if the dissymmetry is larger than X2, judging that a single-phase earth fault occurs at the downstream of the monitoring point, wherein the phases are opposite;
if the transient phase directions of the three-phase currents are consistent, but the dissymmetry of the steady-state interphase amplitude of the three-phase currents is larger than X1, further judging that the dissymmetry is larger than X3, and if the conditions are met, judging that a single-phase grounding fault occurs at the downstream of the monitoring point, wherein the single-phase grounding fault occurs at the downstream of the monitoring pointThe phase not included in the phase sequence is a fault phase;
if the transient phase directions of the three-phase currents are consistent, but the dissymmetry of the steady-state interphase amplitude of the three-phase currents is smaller than X1, judging that a single-phase grounding fault does not occur at the downstream of the monitoring point.
2. The method for judging whether the transient phase directions of the three-phase currents in the step S3 are consistent according to claim 1, wherein the method for judging whether the transient phase directions of the three-phase currents are consistent is as follows:
judging the three-phase current transient phase direction according to whether the three-phase current mutation is larger than 0, if the three-phase current mutation values are larger than 0 or smaller than 0, judging that the directions are consistent, otherwise, judging that the directions are inconsistent.
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