CN115267415A - Single-phase earth fault discrimination method for stock distribution network and terminal thereof - Google Patents
Single-phase earth fault discrimination method for stock distribution network and terminal thereof Download PDFInfo
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Abstract
The invention discloses a single-phase earth fault discrimination method of a stock 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 indicating unit is used for realizing detection, communication and indication of the single-phase earth fault 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 a stock distribution network terminal; extracting fault characteristics of the three-phase transient and steady-state current signals; and on-site judgment of the single-phase earth fault of the distribution network is realized based on the extracted fault characteristics. The method overcomes the dependence of the prior distribution network fault diagnosis on the zero sequence voltage under the condition of not additionally installing a zero sequence voltage transformer, realizes the local judgment of the single-phase earth fault of the distribution network, and solves the problem that the existing distribution network terminal equipment can not 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 earth fault judgment method for a stock distribution network and a terminal thereof.
Background
With the continuous development of urban power grids along with construction, in recent years, more events occur due to the fact that a cable channel is on fire due to single-phase earth faults, and the problem of handling the single-phase earth faults of the urban distribution cable grids is increasingly prominent. The traditional mode of selecting a route through artifical drawing is not only wasted time and energy, still can cause old cable or switchgear insulation breakdown because of taking the overvoltage that the fault operation arouses, further enlarges accident range and harm degree, seriously influences system security and power supply reliability. Therefore, the rapid and accurate detection of the single-phase earth fault has important significance for searching and removing fault points and recovering power supply in time, and has positive effects on ensuring the safety, stability and economic operation of the whole power system.
In China, the neutral point grounding mode of a power distribution network is mainly grounding or non-grounding through an arc suppression coil, and the grounding mode generally belongs to a low-current grounding system and has the measurement characteristics of low fault current, complex electromagnetic environment of measurement environment, unstable grounding arc and extremely short transient signal duration. At the present stage, the distribution line side generally detects the distribution line side through a distribution terminal such as a distribution automation system or a fault indicator, but due to the problems of small fault signals, low sampling rate, poor precision, incomplete existing studying and judging algorithms, communication and the like, the sensitivity is not high, and effective detection of faults generally cannot be realized.
In addition, a part of urban areas with dense population and relatively high reliability of a distribution network structure generally adopt a neutral point grounding mode of grounding through a small resistor, such a grounding mode generally belongs to a large-current grounding system, but when a high-resistance grounding fault occurs, the generated fault current is still small, according to the setting method of the existing zero-sequence over-current protection, when the equivalent resistance value of a grounding transition resistor exceeds 100 omega, the zero-sequence over-current protection cannot effectively detect a single-phase grounding fault, so that the judgment of the single-phase grounding fault needs to be realized through zero-sequence voltage and zero-sequence current, but a zero-sequence voltage transformer is not configured for a distribution line due to the early planning construction considering ferromagnetic resonance and other reasons, and therefore, the existing mature detection device cannot be applied to a line side to realize single-phase grounding fault positioning.
Disclosure of Invention
The purpose of the invention is as follows: in order to overcome the dependence of single-phase earth fault detection of the stock distribution network on zero-sequence voltage and consider that the stock distribution network does not have zero-sequence voltage and zero-sequence current acquisition conditions, the single-phase earth fault judgment method of the stock distribution network and the terminal thereof are provided, the on-site judgment of the single-phase earth fault of the distribution network can be realized, zero-sequence voltage signals do not need to be acquired, the ferroresonance risk is avoided, and the dependence of the conventional distribution network fault diagnosis on the zero-sequence voltage is overcome.
The technical scheme is as follows: in order to achieve the purpose, the invention provides a method for judging the single-phase earth fault of the stock distribution network, which comprises the following steps:
s1: collecting three-phase current signals of a stock distribution network terminal;
s2: extracting fault characteristics of the three-phase transient steady-state current signals:
s3: judging whether the transient phase directions of the three-phase current are consistent or not according to the extracted fault characteristics, and calculating the asymmetry of the steady-state interphase amplitude of the three-phase current;
s4: and based on the data in the step S3, realizing the local judgment of the single-phase earth fault of the distribution network.
Further, the method for extracting the fault characteristics of the three-phase transient and steady-state current signal in step S2 includes:
the method comprises the steps of utilizing a three-phase current signal to self-synthesize a zero-sequence current signal, monitoring that a mutation value of the variation of the zero-sequence current is larger than K, wherein the K is a fixed value and is generally 15-20 mA, further carrying out wavelet packet transformation on the three-phase current and the self-synthesized zero-sequence current, and extracting the asymmetry of the phase of a three-phase current acquisition signal and the amplitude of the phase in a short time window before and after a fault.
Further, the method for calculating the mutation value of the zero sequence current variation in step S2 includes:
k0＝i0(t)-i0(t-T)
wherein ia、ib、icRespectively collecting the current of phase A, phase B and phase C; i all right angle0Is a self-synthesized zero-sequence current value; k is a radical of0The mutation value is the change value of the zero sequence current; and T is a power frequency period.
Further, the method for determining whether the three-phase current transient phase directions in step S3 are consistent includes:
and judging the transient phase direction of the three-phase current according to whether the three-phase current mutation is greater than 0, if the three-phase current mutation values are both greater than 0 or both less than 0, judging that the directions are consistent, otherwise, judging that the directions are inconsistent.
Further, the three-phase current transient phase direction determination formula in step S3 is:
wherein the content of the first and second substances,
the sudden change value of each phase current of A, B, C after load current is filtered through wavelet packet conversion; t is tfaultThe time when the fault occurs; and T is a power frequency period.
Further, the calculation formula of the three-phase current steady-state interphase amplitude asymmetry in the step S3 is as follows:
wherein iab、ibc、icaThe difference of AB, BC and CA phase current after filtering load current through wavelet packet transformation; t is tfaultThe time when the fault occurs; and T is a power frequency period.
Further, the method for locally 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 monitoring point, wherein the phase opposite to the fault phase is the fault phase;
if the transient phase directions of the three-phase currents are inconsistent and the amplitude asymmetry of the stable phases of the three-phase currents is smaller than X1, further expanding the calculation time window of the amplitude asymmetry of the stable phases of the three-phase currents, and if the asymmetry is larger than X2, judging that a single-phase ground fault occurs at the downstream of a monitoring point, wherein the phases opposite to each other are fault phases;
if the transient phase directions of the three-phase currents are consistent, but the asymmetry of the steady-state inter-phase amplitude values of the three-phase currents is larger than X1, further judging that the asymmetry is larger than X3, and if the conditions are met, judging that a single-phase earth fault occurs at the downstream of a monitoring point, wherein
The phase not included in (1) is a fault phase;
and if the transient phase directions of the three-phase currents are consistent, but the asymmetry of the steady-state inter-phase amplitude values of the three-phase currents is smaller than X1, judging that no single-phase earth fault occurs 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 the single-phase earth fault according to the collected three-phase current signals of the stock distribution network terminal.
Furthermore, the current acquisition unit acquires three-phase current signals of the stock distribution network terminal through an 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 acquisition unit, and the other end of the open-close type current transformer is connected with a secondary current acquisition terminal of the stock distribution network terminal through the buckle structure.
Furthermore, the fault detection indicating unit comprises an adaptive power module, a data processing and algorithm processing module and a communication indicating module;
the self-adaptive power supply module is used for providing a working power supply for the fault detection indicating unit;
the data processing and algorithm processing module is used for realizing the detection of the single-phase earth fault;
the communication indication module is used for communication between the distribution network single-phase earth fault judgment terminal and the stock distribution network terminal and the distribution automation main station, so that the realization of functions such as related remote signaling and remote measuring is completed, and the detection and the positioning of the distribution network single-phase earth fault are realized.
Furthermore, a clamping groove and a guide rail which are matched with each other are respectively arranged between the single-phase earth fault judgment terminal of the stock distribution network 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.
Has the beneficial effects that: compared with the prior art, the invention has the following advantages:
1. according to the invention, 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 traditional distribution network fault diagnosis on the zero sequence voltage is overcome, the fault characteristics of the three-phase transient steady-state current signals are extracted by utilizing a high-reliability algorithm such as wavelet packet transformation, and the like, so that the local judgment of the single-phase earth fault of the distribution network 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, high-reliability, flexible and convenient mode.
2. According to the invention, the three-phase current signals are acquired by adopting the opening-closing type current transformer with the buckle structure, and the current signal acquisition can be realized only by buckling the opening-closing type current transformer on the existing protection or metering secondary current loop, so that the safety of live working is improved, and the power failure time is reduced to the greatest extent.
Drawings
Fig. 1 is a schematic connection diagram of a distribution network single-phase earth fault discrimination terminal and a stock 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 ground fault discrimination terminal;
FIG. 4 is a schematic view of a card slot and guide rail;
FIG. 5 is a schematic structural diagram of an open-close type current transformer;
FIG. 6 is a schematic connection diagram of the open-close type current transformer;
FIG. 7 is a schematic wiring diagram of the open-close type current transformer;
FIG. 8 is an internal schematic view of a stock distribution network terminal;
FIG. 9 is k0Schematic diagram of the variation of (1).
Detailed Description
The present invention is further illustrated by the following figures and specific examples, which are to be understood as illustrative only and not as limiting the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalent modifications thereof which may occur to those skilled in the art upon reading the present specification.
As shown in fig. 1, the invention provides a single-phase earth fault discrimination terminal for a 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;
and the fault detection indicating unit is used for realizing the detection, communication and indication of the single-phase earth fault according to the collected three-phase current signals of the stock distribution network terminal.
The fault detection indicating unit comprises a self-adaptive power module, a data processing and algorithm processing module and a communication indicating module;
the self-adaptive power supply module is used for providing a working power supply for the fault detection indicating unit and receiving an external 24-65V direct-current power supply;
the data processing and algorithm processing module is used for realizing the detection of the single-phase earth fault;
the communication indication module is used for communication between the distribution network single-phase earth fault judgment terminal and the stock distribution network terminal and the distribution automation main station, so that the realization of functions such as related remote signaling and remote measuring is completed, and the detection and the positioning of the distribution network single-phase earth fault are realized.
As shown in fig. 2 and fig. 3, the distribution network single-phase ground fault determination terminal specifically includes a housing, and a front panel of the housing is embedded with a status indicator light, wherein the status indicator light is respectively in operation, alarm and ground; the upper end of the shell is embedded into a working power supply interface area, an alternating current analog quantity signal acquisition area and a standby interface area, wherein the working power supply interface area comprises a shell ground and a DC 24V power supply; the lower end of the shell is embedded into 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; a clamping groove is arranged on the rear end panel of the shell and used for clamping a standard guide rail of a DTU or an FTU; the upper end of the shell is sequentially provided with a working power supply 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 sequentially 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 from left to right.
Four types of input/output ports are arranged outside the fault detection indicating unit: the first type input/output port is connected with the current acquisition unit, the second type input/output port is connected with the stock power distribution terminal direct current power supply unit, the third type input/output port is connected with the stock power distribution terminal standby opening unit, and the fourth type input/output port is connected with the stock power distribution terminal wired/wireless communication unit. The size of the shell of the fault detection indicating unit can be adapted to power distribution terminals such as standardized FTUs and DTUs, and DIN buckles are arranged outside the shell and can be fixed on DIN guide rails of stock power distribution terminals.
The hardware system architecture adopts a plug board bus type structure, mainly comprises a CPU module, an AC module, a TRIP module, a power supply module and a communication module, can realize the single-phase earth fault detection function of 1 outlet wire interval, and supports Ethernet communication and RS232/485 communication. The core CPU module adopts a low-power consumption digital signal processor ARM as a main processor, interacts with the AC module to complete current alternating current sampling processing calculation and fault study and judgment, interacts with the TRIP module and the communication module respectively to realize the communication between the power distribution terminal and the power distribution automation main station, and completes the realization of functions such as related remote signaling, remote measurement and the like. The AC module finishes alternating current signal acquisition, a high-speed 16bit and 4-channel synchronous sampling A/D converter is adopted, and the chip integrates an analog power supply, so that the system design can be simplified on one hand, and the hardware cost of an analog channel can be greatly reduced on the other hand. After the AD module finishes synchronous sampling, the sampling value is transmitted to the CPU for processing through the high-speed bus AHB after filtering. The TRIP module is provided with 2 switching value output interfaces and can remotely control 1 protection switching-off outlet and 1 device running state outlet. The power module provides 24V direct current working power. The communication module provides 1 serial port and 1 network port and is responsible for providing a communication function for the terminal.
Referring to fig. 4, a guide rail matched with a card slot of the single-phase earth fault discrimination terminal of the stock distribution network is arranged 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 installed on the stock distribution network terminal through the card slot and the guide rail.
As shown in fig. 5 to 7, the current collection unit collects a three-phase current signal of the storage distribution network terminal through an open-close type current transformer (ct), 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 a secondary current collection terminal of the storage distribution network terminal through a buckle structure.
As shown in fig. 8, for the modification project of the stock power distribution terminal, the installation manner of the device is flexible, the device is suitable for the stock FTU/DTU guide rail, and the device can be fastened in the cabinet body in a distributed manner according to the space of the cabinet body, as shown in fig. 3. Engineering debugging can be remotely realized through a power distribution automation master station, the device supports multiple communication protocols such as IEC60870-5-101, IEC60870-5-104 and the like, multiple media configuration basic information such as Ethernet ports, serial ports, 4G/5G private network communication and the like can be realized through a matched communication server, 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 present embodiment uses the stock distribution network single-phase ground fault determination terminal to perform single-phase ground fault detection on the stock DTU, and provides a stock distribution network single-phase ground fault determination method, which includes the following steps:
s1: collecting three-phase current signals of a stock DTU:
the current acquisition units of the buckling type CT and distribution network single-phase earth fault judgment device realize synchronous acquisition of three-phase current together;
s2: extracting fault characteristics of the three-phase transient and steady-state current signals:
the method comprises the steps of utilizing three-phase current signals to self-synthesize zero-sequence current signals, monitoring the mutation value of the zero-sequence current variation to be larger than K, wherein the K is a fixed value and is selected to be 0.02A in the embodiment, further carrying out wavelet packet transformation on the three-phase current and the self-synthesized zero-sequence current, and extracting the asymmetry of the phase of the three-phase current acquisition signals and the amplitude of the phase interval in a short time window before and after a fault.
In this embodiment, the short time window has a value range (-T, T), and T =0.02s.
The method for calculating the mutation value of the zero-sequence current variable quantity comprises the following steps:
k0＝i0(t)-i0(t-T)
wherein ia、ib、icRespectively collecting the current of phase A, phase B and phase C; i.e. i0Is a self-synthesized zero-sequence current value; k is a radical of0The mutation value is the change value of the zero sequence current; and T is a power frequency period.
S3: judging whether the transient phase directions of the three-phase current are consistent or not according to the extracted fault characteristics, and calculating the asymmetry of the steady-state interphase amplitude of the three-phase current:
the method for judging whether the three-phase current transient phase directions are consistent in the embodiment comprises the following steps:
and judging the transient phase direction of the three-phase current according to whether the three-phase current mutation is greater than 0, if the three-phase current mutation values are both greater than 0 or both less than 0, judging that the directions are consistent, otherwise, judging that the directions are inconsistent.
The three-phase current transient phase direction judgment formula is as follows:
wherein the content of the first and second substances,
the sudden change value of each phase current of A, B, C after load current is filtered through wavelet packet conversion; t is tfaultThe time when the fault occurs; and T is a power frequency period.
The calculation formula of the three-phase current steady-state interphase amplitude asymmetry degree is as follows:
wherein iab、ibc、icaThe difference of AB, BC and CA phase current after filtering load current through wavelet packet transformation; t is tfaultThe time when the fault occurs; and T is a power frequency period.
S4: based on the data of the step S3, the local judgment of the single-phase earth fault of the distribution network is realized:
if the transient phase directions of the three-phase currents are inconsistent and the amplitude asymmetry of the steady-state interphase of the three-phase currents is greater than X1, judging that a single-phase earth fault occurs at the downstream of the monitoring point, wherein the phases opposite to each other are fault phases;
if the transient phase directions of the three-phase currents are inconsistent and the amplitude asymmetry of the stable phases of the three-phase currents is smaller than X1, further expanding the calculation time window of the amplitude asymmetry of the stable phases of the three-phase currents, and if the asymmetry is larger than X2, judging that a single-phase ground fault occurs at the downstream of a monitoring point, wherein the phases opposite to each other are fault phases;
if the transient phase directions of the three-phase currents are consistent, but the asymmetry of the steady-state inter-phase amplitude values of the three-phase currents is larger than X1, further judging that the asymmetry is larger than X3, and if the conditions are met, judging that a single-phase earth fault occurs at the downstream of a monitoring point, wherein
The phase not included in (1) is a fault phase;
and if the transient phase directions of the three-phase currents are consistent, but the asymmetry of the steady-state inter-phase amplitude values of the three-phase currents is smaller than X1, judging that no single-phase earth fault occurs 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, to verify the effectiveness of the method of the present invention, the following example was performed:
taking the occurrence of A-phase grounding fault of the system as an example, filtering calculation is carried out on the mutation value of the zero sequence current variation in S2, and k is0The change of (2) is shown in fig. 9, where point Y is the time when the amount of the abrupt change is greater than the setting value of 0.02A, and the failure determination logic is started.
And calculating the transient phase direction and the steady-state asymmetry of the three-phase current according to the formula in the S3, wherein the results are shown in the following table, the transient phase directions of the three-phase current are inconsistent, and the amplitude asymmetry of the three-phase current at steady-state interphase is greater than X1, so that the single-phase earth fault at the downstream of the monitoring point is judged.
The embodiment also provides a single-phase earth fault judgment system of the stock distribution network, which comprises a network interface, a memory and a processor; the network interface is used for receiving and sending signals in the process of receiving and sending information with other external network elements; a memory for storing computer program instructions executable on the processor; a processor for, when executing the computer program instructions, performing the steps of the consensus method described above.
The present embodiment also provides a computer storage medium storing a computer program that, when executed by a processor, can implement the method described above. The computer-readable medium may be considered tangible and non-transitory. Non-limiting examples of a non-transitory tangible computer-readable medium 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 tapes or hard drives), and optical storage media (e.g., CD, DVD, or blu-ray disc), 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 comprise or rely on stored data. The computer programs may include a basic input/output system (BIOS) that interacts with the hardware of the special purpose computer, a device driver that interacts with specific devices of the special purpose computer, one or more operating systems, user applications, background services, background applications, and the like.
As will be appreciated by one skilled in the art, 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 flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams 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 (10)
1. A single-phase earth fault judgment method for an inventory distribution network is characterized by comprising the following steps:
s1: collecting three-phase current signals of a stock distribution network terminal;
s2: extracting fault characteristics of the three-phase transient and steady-state current signals:
s3: judging whether the transient phase directions of the three-phase current are consistent or not according to the extracted fault characteristics, and calculating the asymmetry of the steady-state interphase amplitude of the three-phase current;
s4: and based on the data in the step S3, realizing the local judgment of the single-phase earth fault of the distribution network.
2. The method for judging the single-phase earth fault of the inventory distribution network according to claim 1, wherein the method for extracting the fault characteristics of the three-phase transient and steady-state current signal in the step S2 comprises the following steps:
the method comprises the steps of utilizing three-phase current signals to self-synthesize zero-sequence current signals, further carrying out wavelet packet transformation on the three-phase currents and the self-synthesized zero-sequence current by monitoring that the mutation value of the zero-sequence current variation is larger than K, and extracting the asymmetry degree of the phase position and the amplitude value between the phase positions of the three-phase current acquisition signals in a short time window before and after a fault.
3. The method for judging the single-phase earth fault of the inventory distribution network according to claim 2, wherein the method for calculating the mutation value of the zero-sequence current variation in the step S2 comprises the following steps:
k0＝i0(t)-i0(t-T)
wherein ia、ib、icRespectively collecting the current of phase A, phase B and phase C; i all right angle0Is a self-synthesized zero-sequence current value; k is a radical of0The mutation value is the change value of the zero sequence current; and T is a power frequency period.
4. The method for judging the single-phase earth fault of the stock distribution network according to claim 1, wherein the method for judging whether the transient phase directions of the three-phase currents are consistent in the step S3 is as follows:
and judging the transient phase direction of the three-phase current according to whether the three-phase current mutation is greater than 0, if the three-phase current mutation values are both greater than 0 or both less than 0, judging that the directions are consistent, otherwise, judging that the directions are inconsistent.
5. The method for judging the single-phase earth fault of the inventory distribution network according to claim 4, wherein the three-phase current transient phase direction judgment formula in the step S3 is as follows:
wherein the content of the first and second substances,
the sudden change value of each phase current of A, B, C after load current is filtered through wavelet packet conversion; t is tfaultThe time when the fault occurs; and T is a power frequency period.
6. The method for judging the single-phase earth fault of the inventory distribution network according to claim 1, wherein the calculation formula of the three-phase current steady-state interphase amplitude asymmetry in the step S3 is as follows:
wherein iab、ibc、icaThe difference of AB, BC and CA phase current after load current is filtered out through wavelet packet transformation; t is tfaultThe time when the fault occurs; and T is a power frequency period.
7. The method for judging the single-phase earth fault of the distribution network on the basis of the claim 1, wherein the method for locally judging the single-phase earth fault of the distribution network in the step S4 comprises the following steps:
a single-phase earth fault occurs downstream of the monitoring point, wherein the phase opposite to the fault phase is the fault phase;
if the transient phase directions of the three-phase currents are inconsistent and the amplitude asymmetry of the stable phases of the three-phase currents is smaller than X1, further expanding the calculation time window of the amplitude asymmetry of the stable phases of the three-phase currents, and if the asymmetry is larger than X2, judging that a single-phase ground fault occurs at the downstream of a monitoring point, wherein the phases opposite to each other are fault phases;
if the transient phase directions of the three-phase currents are consistent, but the asymmetry of the steady-state inter-phase amplitude values of the three-phase currents is larger than X1, further judging that the asymmetry is larger than X3, and if the conditions are met, judging that a single-phase earth fault occurs at the downstream of a monitoring point, wherein
The phase not included in (1) is a fault phase;
and if the transient phase directions of the three-phase currents are consistent, but the asymmetry of the steady-state inter-phase amplitude values of the three-phase currents is smaller than X1, judging that no single-phase earth fault occurs at the downstream of the monitoring point.
8. A single-phase earth fault discrimination terminal of a stock distribution network is characterized by comprising 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 the single-phase earth fault according to the collected three-phase current signals of the stock distribution network terminal.
9. The single-phase earth fault distinguishing terminal of the stock distribution network according to claim 8, wherein the current collecting unit collects three-phase current signals of the stock distribution network terminal through an 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 collecting unit, and the other end of the open-close type current transformer is connected with a secondary current collecting terminal of the stock distribution network terminal through a buckle structure.
10. The single-phase earth fault discrimination terminal for the inventory distribution network according to claim 8, characterized in that the fault detection indication unit comprises an adaptive power 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 indicating unit;
the data processing and algorithm processing module is used for realizing the detection of the single-phase earth fault;
the communication indication module is used for communication between the distribution network single-phase earth fault judgment terminal and the stock distribution network terminal and the distribution automation main station, and detection and positioning of the distribution network single-phase earth fault are achieved.
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