Device and method for online monitoring of distribution network cable faults based on transient residual current

Abstract

The present invention relates to an online monitoring device and method for distribution network cable faults based on transient residual current. The device is arranged on a three-phase cable outside a ring network cabinet, and includes a Rogowski coil inductor, a collector, a memory, an embedded computing module, a fault arc identification module and a communication module. The collector is connected to the Rogowski coil inductor and the embedded computing module, the embedded computing module is also connected to the memory and the fault arc identification module, the fault arc identification module is connected to the communication module, and the communication module is wirelessly connected to a master station. Compared with the prior art, the distribution network cable fault online monitoring device of the present invention only collects the unique parameter of the residual current of the three-phase cable, and the ring network cabinet does not need to be powered off for installation, and the power supply reliability of the power grid is not affected. The online monitoring and identification of the fault of the three-phase cable of the distribution network is completed, and the fault arc identification module is provided to re-identify the fault waveform data, thereby improving the accuracy of fault identification.

Description

Technical Field

[0001] The present invention relates to the field of distribution network fault detection, and in particular to a distribution network cable fault online monitoring device and method based on transient residual current. Background Art

[0002] The multi-branch distribution network composed of power supply, ring network cabinet and cable is the basic infrastructure for power supply guarantee. However, due to external environment and internal quality, the short circuit fault between phases of three-phase cables in the distribution network will affect the reliability of power supply. Once the cable fails, it is necessary to quickly know the fault location and eliminate the fault as soon as possible.

[0003] However, due to the crisscrossing of cables in the three-phase distribution network with multi-level distribution, the fault location was previously found manually, which was inefficient. Therefore, it is necessary to install online monitoring devices on the cables to understand the fault information and improve work efficiency. Among them, the primary task of the online monitoring device is to quickly and accurately identify the interphase short circuit fault of the distribution network cable.

[0004] Therefore, the current online monitoring device for cable phase-to-phase short-circuit fault basically adopts the installation of current and voltage sensors at the phase and ground ends of the cable to collect the current, voltage and phase of the phase and ground lines of the cable, and detect the phase-to-phase short-circuit fault of the cable based on this data. At the same time, the influence of interference such as load changes and lightning on the accuracy of cable fault identification is eliminated through identification methods such as the sudden change amount, cycle or frequency band filtering of the waveform.

[0005] However, the three-phase cables used in the current distribution network are connected to the ring main unit in sections or branches. In many cases, the cable phase connection is implemented in the ring main unit. Therefore, according to the above conventional online monitoring method, it is necessary to install current and voltage sensors for the cable phase line and ground line in the ring main unit after the power outage of the distribution network. This will greatly affect the power supply reliability of the distribution network. Therefore, it is necessary to provide an online monitoring device for phase-to-phase short-circuit cable faults in the distribution network that can be installed without power outage. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide an online monitoring device and method for distribution network cable faults based only on transient residual current.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A distribution network cable fault online monitoring device based on transient residual current includes a power supply for powering the device. The cable fault online monitoring device is arranged on a three-phase cable outside a ring network cabinet. The cable fault online monitoring device includes a Rogowski coil sensor, a collector, a memory, an embedded computing module, a fault arc identification module and a communication module. The collector is connected to the Rogowski coil sensor and the embedded computing module. The embedded computing module is also connected to the memory and the fault arc identification module. The fault arc identification module is connected to the communication module. The communication module is wirelessly connected to a master station. The Rogowski coil sensor includes an open Rogowski coil.

[0009] Furthermore, the Rogowski coil inductor also includes an integrator, which connects the open Rogowski coil and the collector. The open Rogowski coil responds to the electromagnetic field changes caused by the residual current of the three-phase cable in real time, and these changes are converted into digital signals through the sensing of the high-frequency integrator and sent to the collector.

[0010] Furthermore, the arc fault identification module is an FPGA chip or a CPU integrated with arc fault identification software.

[0011] Furthermore, the collector is a collector that is timed by GPS / Beidou navigation satellites.

[0012] Furthermore, the embedded computing module is an FPGA chip or a CPU.

[0013] Furthermore, the memory is a stack memory.

[0014] Furthermore, the integrator is a high-frequency integrator, the collector is a high-speed clock-synchronized collector, and the memory is a high-speed memory.

[0015] A method for online monitoring of distribution network cable faults using the above device, the method comprising the following steps:

[0016] Device installation steps: non-invasively install the Rogowski coil inductor on the three-phase cable outside the ring main cabinet;

[0017] Data collection steps: The collector collects the digital signal obtained by the open Rogowski coil and converted by the integrator in real time, synthesizes the three-phase cable residual current data with time stamp through the embedded computing module and stores it in the memory;

[0018] Data acquisition step: the embedded computing module acquires the three-phase cable residual current data in the memory;

[0019] Initial fault identification step: The embedded computing module identifies suspected fault waveform data with mutation and transient characteristics from the three-phase cable residual current data;

[0020] Fault re-identification step: The fault arc identification module identifies the fault waveform data with fault arc characteristics from the suspected fault waveform data with mutation and transient characteristics; the fault re-identification step is based on the fact that cable short circuit and grounding fault must have fault arc, and the arc will inevitably generate a harmonic spectrum with fault arc characteristics on the line. By re-identifying the suspected fault waveform data with mutation and transient characteristics, the waveform with fault arc characteristics is extracted, and the waveform belonging to the normal disturbance range is filtered out, thereby improving the accuracy of distinguishing three-phase cable faults in the distribution network.

[0021] Fault reporting steps: The fault arc identification module reports the fault waveform data with fault arc characteristics to the main station through the communication module.

[0022] Furthermore, in the preliminary fault identification step, the method by which the embedded computing module identifies fault waveform data having mutation and transient characteristics includes second-level delay avoidance and / or specific frequency band bandpass filtering.

[0023] Furthermore, the fault waveform data includes residual current waveform data and time information data.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] (1) The present invention obtains the transient residual current of the three-phase cable through the Rogowski coil sensor, and realizes the online monitoring of the phase-to-phase short-circuit fault of the three-phase cable of the distribution network only through the transient residual current parameter. The Rogowski coil sensor is installed on the three-phase cable outside the ring network cabinet. During installation, there is no need to cut off the power supply of the ring network cabinet, and the power supply reliability of the power grid is not affected.

[0026] (2) The distribution network cable fault online monitoring device of the present invention is provided with a fault arc identification module, which improves the recognition accuracy of the distribution network cable fault online monitoring device of the present invention for three-phase cable short-circuit faults by re-identifying the fault waveform data with fault arc characteristics from the suspected fault waveform data with mutation and transient characteristics.

[0027] (3) The collector of the online monitoring device for distribution network cable faults of the present invention is timed by GPS / Beidou navigation satellites, so that the acquired fault waveform data carries time information data, further providing an accurate analysis and judgment basis for finally determining the location of the faulty cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of the online monitoring device for cable faults in the power distribution network of the present invention;

[0029] Figure 2 It is a flow chart of an online monitoring method for distribution network cable faults;

[0030] Figure 3 This is a schematic diagram of the distribution network architecture;

[0031] Figure 4 It is a schematic diagram of the structure of a three-phase cable. DETAILED DESCRIPTION

[0032] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0033] Example 1

[0034] like Figure 1 As shown, this embodiment is an online monitoring device for cable faults in a distribution network based on transient residual current, including a power supply 1 for supplying power to the online monitoring device for cable faults. The online monitoring device for cable faults is arranged on a three-phase cable outside the ring network cabinet. The online monitoring device for cable faults includes a Rogowski coil sensor 2, a collector 3, a memory 4, an embedded computing module 5, a fault arc identification module 6 and a communication module 7. The collector 3 is connected to the Rogowski coil sensor 2 and the embedded computing module 5. The embedded computing module 5 is also connected to the memory 4 and the fault arc identification module 6. The fault arc identification module 6 is connected to the communication module 7. The communication module 7 is wirelessly connected to a master station 8. The Rogowski coil sensor 2 includes an open Rogowski coil 201.

[0035] The components of the online monitoring device for cable faults in the distribution network of this embodiment are described in detail below:

[0036] 1. Rogowski coil sensor 2

[0037] The Rogowski coil inductor 2 is composed of an open Rogowski coil 201 and an integrator 202. The Rogowski coil 201 is a non-invasive open Rogowski coil, and the integrator 202 is a high-frequency integrator 202. The non-invasive open Rogowski coil is installed on the three-phase cable outside the ring main unit without powering off the ring main unit. The open Rogowski coil 201 responds to the electromagnetic field changes caused by the residual current of the three-phase cable in real time. These changes are converted into digital signals through the sensing of the high-frequency integrator 202 and sent to the collector 3.

[0038] 2. Collector 3

[0039] The collector 3 is a high-speed clock-synchronized collector 3, which can be a high-speed collector 3 timed by GPS / Beidou navigation satellite. The collector 3 collects the digital signal converted by the Rogowski coil inductor 2 online, and generates time-stamped three-phase cable residual current data in the control system of the embedded computing module 5, and stores the data in the memory 4.

[0040] 3. Memory 4

[0041] The memory 4 of this embodiment adopts a high-speed memory. The memory 4 stores and updates a plurality of three-phase cable residual current data with time stamps in a stacked manner, and synthesizes them into three-phase cable residual current waveform data with time stamps, and pushes them to the embedded computing module 5 according to their timing.

[0042] 4. Embedded computing module 5

[0043] The embedded computing module 5 is a CPU and contains control software stored in the control memory 4 and related computing software for identifying the waveform data of residual current of three-phase cables, and identifies suspected fault waveform data with mutation and transient characteristics.

[0044] The identification measures implemented by the relevant calculation software for identifying the residual current waveform data of three-phase cables include second-level delay avoidance and specific frequency band bandpass filtering.

[0045] 5. Arc fault identification module 6

[0046] In order to improve the recognition accuracy of the phase-to-phase short-circuit fault waveform of the residual current of the three-phase cable by the device of the present invention, in addition to adopting conventional anti-interference waveform data identification measures such as second-level delay avoidance and specific frequency band bandpass filtering, based on the arc characteristics when a short-circuit fault occurs in the cable, a fault arc identification module 6 with an automatic identification function of fault arc characteristics is also embedded in the device of the present invention.

[0047] The arc fault identification module 6 in this embodiment is an FPGA chip integrated with arc fault identification software.

[0048] The arc fault identification module 6 re-identifies the suspected fault waveform data with mutation and transient characteristics identified by the embedded computing module 5, so as to improve the recognition accuracy of the distribution network phase-to-phase short-circuit cable fault of the device of the present invention.

[0049] The arc fault identification module 6 identifies the fault waveform data with arc fault characteristics from the suspected fault waveform data with mutation and transient characteristics. The fault waveform data with arc fault characteristics is data information consisting of a transient residual current waveform and time information data caused by a three-phase cable phase-to-phase short circuit fault.

[0050] This embodiment determines the fault waveform data having the fault arc characteristics by identifying the duration, transient state, and phase characteristics of the waveform.

[0051] like Figure 3 and Figure 4As shown, the distribution network includes a power supply, a ring main unit and a cable, and the ring main unit is connected to the power consumption side through a cable. The three-phase cable includes phase A, phase B and phase C, which are respectively used to access phase A, phase B and phase C of three-phase switch cabinet power equipment such as the distribution network ring main unit. By installing the device of the present invention on each section of the three-phase cable of the distribution network, the transient residual current waveform and time information data uploaded by it caused by the interphase short circuit fault of the three-phase cable will provide accurate analysis and judgment basis for the background master station 8 to finally determine the location of the faulty cable on the distribution network architecture.

[0052] The arc fault identification module 6 and the arc fault identification method of the device of the present invention can be used not only for online identification of interphase short circuit faults of three-phase cables, but also for online identification of other types of cable faults.

[0053] Example 2

[0054] like Figure 2 As shown, this embodiment is a method for online monitoring of distribution network cable faults using the device of embodiment 1, and the method includes the following steps:

[0055] Device installation steps: non-invasively install the Rogowski coil inductor 2 on the three-phase cable outside the ring main unit;

[0056] Data collection step: the collector 3 collects the digital signal obtained by the open Rogowski coil 201 and converted by the integrator 202 in real time, synthesizes the three-phase cable residual current data through the embedded computing module 5 and stores it in the memory 4;

[0057] Data acquisition step: the embedded computing module 5 acquires the three-phase cable residual current data in the memory 4;

[0058] Preliminary fault identification step: the embedded computing module 5 identifies suspected fault waveform data with mutation and transient characteristics from the three-phase cable residual current data; wherein the method by which the embedded computing module 5 identifies the fault waveform data with mutation and transient characteristics includes second-level delay avoidance and specific frequency band bandpass filtering;

[0059] Fault re-identification step: the fault arc identification module 6 identifies the fault waveform data with fault arc characteristics from the suspected fault waveform data with mutation and transient characteristics; the fault waveform data includes residual current waveform data and time information data;

[0060] Fault reporting step: the arc fault identification module 6 reports the fault waveform data with arc fault characteristics to the main station 8 through the communication module 7.

[0061] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A distribution network cable fault online monitoring device based on transient residual current, comprising a power supply (1) for supplying power to the device, characterized in that: The cable fault online monitoring device is arranged on a three-phase cable outside the ring network cabinet, and comprises a Rogowski coil inductor (2), a collector (3), a memory (4), an embedded computing module (5), a fault arc identification module (6) and a communication module (7); the collector (3) is connected to the Rogowski coil inductor (2) and the embedded computing module (5); the embedded computing module (5) is also connected to the memory (4) and the fault arc identification module (6); the fault arc identification module (6) is connected to the communication module (7); the communication module (7) is wirelessly connected to a master station (8); the Rogowski coil inductor (2) comprises an open Rogowski coil (201); the Rogowski coil inductor (2) further comprises an integrator (202); the integrator (202) is connected to the open Rogowski coil (201) and the collector (3); The steps for online monitoring of distribution network cable faults include: Device installation steps: non-invasively install the Rogowski coil inductor (2) on the three-phase cable outside the ring main cabinet; Data collection step: the collector (3) collects in real time the digital signal obtained by the open Rogowski coil (201) and converted by the integrator (202), synthesizes the three-phase cable residual current data through the embedded computing module (5) and stores it in the memory (4); Data acquisition step: the embedded computing module (5) acquires the three-phase cable residual current data in the memory (4); A preliminary fault identification step: the embedded computing module (5) identifies suspected fault waveform data with mutation and transient characteristics from the three-phase cable residual current data, wherein the method for the embedded computing module (5) to identify the fault waveform data with mutation and transient characteristics includes second-level delay avoidance and / or specific frequency band bandpass filtering; Fault re-identification step: the fault arc identification module (6) identifies the fault waveform data with fault arc characteristics from the suspected fault waveform data with mutation and transient characteristics, wherein the fault waveform data with fault arc characteristics includes data information consisting of a transient residual current waveform and time information data caused by a three-phase cable interphase short circuit fault; Fault reporting step: the fault arc identification module (6) reports the fault waveform data having the fault arc characteristics to the main station (8) through the communication module (7); The above device realizes online monitoring of the interphase short-circuit fault of the three-phase cable in the distribution network by only using one parameter, the transient residual current.

2. The online monitoring device for distribution network cable fault based on transient residual current according to claim 1 is characterized in that: The arc fault identification module (6) is an FPGA chip or a CPU integrated with arc fault identification software.

3. The online monitoring device for distribution network cable fault based on transient residual current according to claim 1 is characterized in that: The collector (3) is a collector that is timed by GPS / Beidou navigation satellites.

4. The online monitoring device for distribution network cable fault based on transient residual current according to claim 1 is characterized in that: The embedded computing module (5) is an FPGA chip or a CPU.

5. The online monitoring device for distribution network cable fault based on transient residual current according to claim 1 is characterized in that: The memory (4) is a stack memory.

6. The online monitoring device for distribution network cable fault based on transient residual current according to claim 1 is characterized in that: The integrator (202) is a high-frequency integrator, the collector (3) is a high-speed clock-synchronized collector, and the memory (4) is a high-speed memory.

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