CN201051663Y - Single phase ground failure location device for neutral point indirect ground power grid - Google Patents

Abstract

The utility model discloses a single-phase grounding fault location device for a neutral point non-directly grounded power grid, which is composed of a host, host analysis software, switch monitoring control terminal, transformer detection terminal, etc. In the event of a short-circuit fault, the switch monitoring control terminal installed at the switch on the column or at the ring network cabinet collects the zero-sequence current information of the line where the switch monitoring control terminal is installed before and after the moment of the fault, and then sends the zero-sequence current information to the host computer for further processing. Analyze and compare to obtain the information of the faulty section of the line, and isolate the faulty section to ensure the power supply to the non-faulty section.

Description

Single-phase ground fault location device for neutral point non-directly grounded power grid

technical field

The utility model relates to a rapid location and restoration of power supply for single-phase grounding or short-circuit faults of a power grid, in particular to a single-phase grounding or inter-phase short-circuit fault location device for an indirect neutral point grounding power grid, which belongs to the technical field of power supply.

Background technique

The neutral point operation mode of my country's 66 kV and below power grid (also known as power distribution system) generally adopts the neutral point non-directly grounded operation mode (that is, the neutral point is not grounded or the neutral point is grounded through the arc suppression coil) . In the neutral point non-directly grounded operating system, when a single-phase ground fault occurs, it is difficult to completely solve the single-phase ground fault due to the characteristics of small short-circuit current and ground instability caused by arc light. How to quickly determine the line fault location, quickly isolate the fault and restore the power supply to users as soon as possible is a problem that people generally care about. But so far, people have only studied and solved the problem of how to select which line is the faulty line in the case of multiple outgoing lines in the substation, and how to find the ground fault point as soon as possible after the faulty line is selected, and then quickly restore the non-faulty line. The power supply of the section has been using the relatively primitive method of manual line inspection. Not only will it take a lot of manpower, but it will also cause power outages to the electricity users of the entire line, ranging from a few hours to dozens of hours, or even longer, affecting the normal supply of electricity.

At present, Chinese scientific researchers have also carried out some research on the fault judgment method of distribution lines, such as: the invention patent application with the application number 0114452.9 published on September 6, 2000 provides a "grounding protection method for small current grounding system" , which includes the following steps: ①Monitor the zero-sequence voltage and negative-sequence current of the system; ②When the zero-sequence voltage is greater than the set voltage, determine that the system has a grounding or disconnection fault; ③Calculate the negative-sequence current change ΔI2; ④When a line |ΔI2|＞|Is|, and |ΔI2|＞setting value, it is determined that the line is faulty. The above-mentioned patent applications and existing single-phase ground fault protections that have been put into practical use can only realize the line selection function of ground faults. Generally, it is necessary to collect and compare the power information of each outgoing line to determine the single-phase ground fault line, which cannot be adapted to automatic fault areas for feeders. Segments are automatically identified to isolate development requirements.

Contents of the invention

The purpose of this utility model is to propose a device for locating single-phase grounding or phase-to-phase short-circuit faults in neutral point non-directly grounded power grids in view of the shortcomings of the prior art. The utility model can quickly determine the fault section of the line, And quickly isolate the fault point to ensure the power supply to the non-faulty section.

The purpose of this utility model is achieved by the following technical solutions:

The single-phase ground fault location device of neutral point non-directly grounded power grid is composed of host, host analysis software, monitoring control terminal, transformer monitoring terminal and so on. Each monitoring and control terminal is installed at the switch on the distribution line column or at the ring network cabinet, and the synchronization of the signal acquisition time is maintained by the GPS satellite timing synchronization clock between the monitoring and control terminals; the host computer, the monitoring and control terminal, and the transformer monitoring terminal are Use GPRS/GSM wireless communication or wired communication to transmit data or issue control commands.

The principle of the utility model for judging the single-phase grounding fault section of the neutral point indirect grounding power distribution system is:

1. When a single-phase ground fault occurs in the power distribution system whose neutral point is not grounded, all substations shall

Both the main line and the branch line of the distribution line have zero-sequence current passing through. The steady-state and transient zero-sequence currents of the main line and branch lines of distribution lines meet the following conditions:

① The steady-state and transient zero-sequence currents passed by the faulty line are the sum of the capacitive currents of all non-faulty lines, and the direction is from the line to the bus;

②The steady-state and transient zero-sequence current of non-fault lines (including non-fault branch lines of fault lines) is the capacitive current of the line itself, and the direction is from the bus to the line;

③The steady-state and transient zero-sequence current passed by the faulty branch line of the faulty line is the sum of the capacitive current of all non-faulty lines and the non-faulty branch line of the faulty line, and the direction is from the line to the bus;

④ If the zero-sequence current direction of all lines flows from the bus to the line, the single-phase ground fault occurs in the substation bus.

2. In the overcompensated operation state of the power distribution system whose neutral point is grounded through the arc suppression coil, when a single-phase ground fault occurs, the steady-state and transient zero-sequence currents no longer meet the above conditions, but the fifth harmonic current still meets the above conditions;

3. In the overcompensated operation state of the power distribution system whose neutral point is grounded through the arc suppression coil, during a single-phase ground fault in the system, if the reactance or impedance parameters of the arc suppression coil are changed for a short time, then: the fault line and the non-fault line The zero-sequence current of the line will change accordingly. Among them, the variation of zero-sequence current of the fault line is the largest.

When a single-phase ground fault occurs in a power distribution system whose neutral point is not grounded, the single-phase ground fault location device of the neutral point non-directly grounded power distribution system is realized as follows:

First of all, the substation bus voltage transformer monitoring terminal detects that the output voltage of the substation bus voltage transformer opening delta reaches the preset value, and the bus voltage transformer monitoring terminal notifies the host computer that a single-phase ground fault has occurred in the power distribution system through GPRS/GSM communication. Then the host computer notifies all the monitoring and control terminals to intercept and store the fault zero-sequence current waveform data before and after the moment of the fault, and transmit the waveform data to the host computer through GPRS/GSM wireless communication. From the amplitude and phase of the transient and steady-state zero-sequence currents measured by the terminal, four zero-sequence current lines with the largest amplitudes are selected (not considered if the zero-sequence current amplitude is too small), and the zero-sequence current amplitude Value and phase comparison (horizontal comparison), according to the above single-phase ground fault criterion, to determine which line has a single-phase ground fault. When it is determined that a single-phase ground fault has occurred on a certain line, analyze and compare the waveform data sent back by all monitoring and control terminals installed on the line (vertical comparison, but this time does not include other non-faulty line switches ), analyze and judge the magnitude and phase of the transient and steady-state zero-sequence currents measured by all monitoring and control terminals of the line with the fault criterion of single-phase grounding, and finally according to the fault criterion of single-phase grounding, the zero A group of switches through which the sequence current flows from the line to the bus is the path through which the fault zero-sequence current of the ground point flows. Therefore, the location of the line fault section can be determined by the host computer software. At this time, the host automatically notifies the relevant staff of the faulty section information through computer screen display, sound and light alarm, and mobile phone text messages. Based on this, the on-duty personnel can remotely control and disconnect a switch in front of the faulty section through the computer (it can also be set to computer-controlled automatic disconnection). Thus, the fault of the grounding point is cut off and isolated, and the output voltage of the open triangle of the busbar transformer returns to normal.

When a single-phase ground fault occurs in the power distribution system whose neutral point is grounded through the arc suppression coil, the single-phase ground fault location device of the neutral point non-directly grounded power grid is implemented as follows:

First of all, the substation bus voltage transformer monitoring terminal detects that the output voltage of the substation bus voltage transformer opening delta reaches the pre-set value, and the bus voltage transformer monitoring terminal notifies the host through GPRS/GSM wireless communication that a single-phase grounding has occurred in the power distribution system At the same time, the gear of the neutral point arc suppressing coil is automatically lowered or raised by one gear from a certain gear before grounding in about 3 seconds, and then returns to the original grounding position Gear position, at this time, the host will notify all monitoring and control terminals to intercept and store the zero-sequence current waveform data before and after the moment of failure and before and after the gear change of the arc suppression coil, and transmit the waveform data to The main engine, the main engine first analyzes and compares the changes of the zero-sequence current measured by the monitoring and control terminals of the outlet switches in the substation. Then, in the process of returning to the original gear before grounding, the zero-sequence current of all outgoing lines in the substation will change to a certain extent. Indicates that a single-phase-to-earth fault has occurred on the line. This line is the single-phase-to-ground fault line. Next, analyze and compare the change of the zero-sequence current measured by all monitoring and control terminals on the line. If the zero-sequence current measured by a certain number of monitoring and control terminals in the line occurs If the zero-sequence current measured by the switch monitoring control terminal in the line substation has the same magnitude of change, it means that the single-phase ground fault current flows through the group of switches. Therefore, the position of the line fault section can be obtained by judging by the host computer analysis software. At this time, the host automatically notifies the relevant staff of the faulty section information through computer screen display, sound and light alarm, and mobile phone text messages. Based on this, the on-duty personnel can remotely control and disconnect a switch in front of the faulty section through the computer (it can also be set to automatically disconnect the switch under computer control). Thus, the fault of the grounding point is cut off and isolated, and the output voltage of the open triangle of the busbar transformer returns to normal.

When a phase-to-phase short-circuit fault occurs in a power distribution system whose neutral point is ungrounded and grounded through an arc-suppression coil, the single-phase ground fault location device of the neutral point non-directly grounded power grid is implemented as follows:

When a phase-to-phase short-circuit fault occurs in a power distribution system whose neutral point is ungrounded and grounded through an arc-suppression coil, the switch in the substation of the faulty line and the current transformer attached to the switch on the column all feel a shock that exceeds the normal operating current of the line by more than several times. For short-circuit fault current, the monitoring and control terminal connected to the current transformer (CT) inside the switch collects and stores the relevant data of this fault current, and compares it with the preset given value (setting value). If the current exceeds the given data of the set value, the group of monitoring and control terminals will send the current data together with the judgment conclusion to the host by GPRS/GSM wireless communication. At this time, if the fault point is an instantaneous phase-to-phase short-circuit fault, the outlet switch in the substation will reclose successfully after the first disconnection. The line monitoring and control terminal will sense the normal working current after the first instant fault current is detected and after a reclosing interval of 0.5 seconds (the line has no current at this moment), at this time the monitoring and control terminal of the fault line will report to the host Report a momentary short circuit fault on the line. The host computer notifies the relevant staff of the momentary fault section information through computer screen display, sound and light alarm and mobile phone text message. If a permanent phase-to-phase short-circuit fault occurs at the fault point, the outlet switch of the faulty line in the substation will fail to reclose after the first disconnection, and after a reclosing time of 0.5 seconds (there is no current in the line at this moment), it will be monitored for the second time When the fault current is detected, the switch of the faulty line in the substation will be disconnected for the first time. At this time, all monitoring and control terminals of the faulty line will report to the host computer that a permanent short-circuit fault has occurred on the line, and the display screen of the host computer will display the distance passed by the short-circuit current. Path, the computer automatically marks the switches that the short-circuit current passes through and changes them to other colors. At this time, the host computer notifies the relevant staff of the fault section information through computer screen display, sound and light alarm and mobile phone short message. Based on this, the personnel on duty will control and disconnect the first switch before the fault point through the computer (at this time, the system can also be set to automatically execute the first switch before disconnecting the fault point), thereby cutting off the faulty part of the line. After the switch is disconnected, the staff will notify the substation operator to close the outlet switch of the faulty line in the substation according to the fault isolation prompt on the computer screen, so that the fault-free section of the line can resume power transmission in the shortest possible time .

The beneficial effect of the utility model is: it is applied to the non-directly grounded power distribution system of 66 kV and below, when the system has a single-phase grounding and phase-to-phase short-circuit fault, it can quickly determine and cut off the faulty section of the line, Therefore, it is realized that the fault-free section of the line can restore power supply in the shortest possible time. The automation level of the power grid has been improved.

Description of drawings

Fig. 1 is a schematic diagram of the relationship between each component of the utility model;

Fig. 2 is a working block diagram of the monitoring control terminal and the host computer of the utility model.

In the picture:

  主机

the host

    为变电站开关监测控制终端

Control terminal for substation switch monitoring

    为线路开关监测控制终端

Control terminal for line switch monitoring

     TV为线路电压互感器

TV is the line voltage transformer

   互感器监测终端

Transformer monitoring terminal

     为变电站出线开关

Outlet switch for substation

      为线路柱上开关(或环网柜开关)

It is the switch on the line column (or the switch of the ring network cabinet)

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment the utility model is further described:

As shown in Figure 1, when a single-phase ground fault occurs at point d1, the implementation of the single-phase ground fault location device in the neutral point indirect ground distribution system is as follows:

(1) When a single-phase ground fault occurs in the power distribution system with an ungrounded neutral point as shown in Figure 1: first, the monitoring terminal RV of the bus voltage transformer in the substation detects that the open delta output voltage of the bus voltage transformer in the substation reaches the pre-set value The busbar transformer monitoring terminal RV notifies the host MA system of a single-phase ground fault through GPRS/GSM wireless communication, and then the host MA notifies all substation switch monitoring control terminals ZD1, ZD2, ... ZDn to intercept and store the moment when the fault occurs The zero-sequence current waveform data before and after the fault, and transmit the data to the host MA through GPRS/GSM wireless communication, and the host MA selects 4 zero-sequence current lines with the largest amplitude (the zero-sequence current amplitude is too small and will not be Consider), compare the zero-sequence current amplitude and phase (horizontal comparison), and determine which line has a single-phase ground fault according to the above-mentioned single-phase ground fault criterion. When it is determined that a single-phase ground fault has occurred on line 3, compare the waveform data returned by all monitoring and control terminals ZD and ZS on line 3 (vertical comparison), and analyze all monitoring and control terminals of this line with the same judgment method as above. The amplitude and phase of the zero-sequence current measured by the terminals ZS and ZD, and finally according to the above single-phase ground fault criterion, the zero-sequence current measured by the monitoring and control terminals ZD3, ZS1, ZS4 and ZS5, and its phase It is opposite to the phase of the zero-sequence current measured by other monitoring and control terminals, so it is determined that the fault point is located on the branch line 5. At this time, the host MA automatically notifies the relevant staff of the fault section information by means of computer screen display, sound and light alarm and mobile phone short message. The staff on duty can click the disconnect switch S5 through the computer mouse accordingly. Thereby eliminating the fault of the grounding point of the branch line 5, and the output voltage of the open triangle returns to normal. Therefore, the power supply of the non-faulty section of the line 3 is guaranteed.

(2) When a single-phase ground short-circuit fault occurs at point d1 of the power distribution system whose neutral point is grounded through the arc-suppression coil as shown in Figure 1: the gear of the neutral-point arc-suppression coil is within about 3 seconds after the fault occurs , from a certain gear before grounding, down one gear or up one gear, and then return to the original gear before grounding. At this time, first analyze the monitoring and control terminals ZD1, ZD2, ... ZDn of each outlet switch in the substation The change of the measured zero-sequence current. At this time, it can be measured that the zero-sequence current measured by the substation outgoing line 3 monitoring control terminal ZD3 has the largest change before and after the moment of the fault and before and after the gear of the arc suppression coil, while other The variation of the zero-sequence current of the outgoing line of the substation is obviously smaller than the variation of the zero-sequence current measured by the monitoring control terminal ZD3 of the substation outgoing line 3. Explain that single-phase ground occurs on line 3. Next, analyze and compare the changes of the zero-sequence currents of all monitoring and control terminals ZD and ZS on line 3. It can be seen that the changes of the zero-sequence currents measured by the monitoring and control terminals ZD3, ZS1, ZS4 and ZS5 are basically the same, and are obviously larger than this The variation of zero-sequence current measured by other monitoring and control terminals of the line. Therefore, it is determined that the fault point is located on the branch line 5.

(3) When the neutral point shown in Figure 1 is not grounded or the distribution system d1 point is grounded through the arc suppression coil, when a phase-to-phase short circuit fault occurs, the specific implementation of the present invention is as follows:

At this time, the built-in current transformers of switches D3, S1, S4, and S5 all feel the short-circuit fault current that exceeds the normal operating current of the line in a relatively short period of time, while other switches in the power distribution system do not feel it. When the short-circuit fault current is reached, the monitoring and control terminals ZD3, ZS1, ZS4, and ZS5 connected to the current transformer (CT) attached to the switch record and store the relevant data of the fault current, and compare it with the preset given value (setting value) for comparison, if the current exceeds the given data of the setting value, the monitoring control terminals ZD3, ZS1, ZS4, ZS5 will send the current data together with the judgment conclusion to the host MA through GPRS/GSM wireless communication. At this time, if the d1 fault point is an instantaneous phase-to-phase short-circuit fault, the switch D3 in the substation will successfully reclose after being disconnected for the first time. The monitoring and control terminals ZD3, ZS1, ZS4, and ZS5 will sense the normal working current after a 0.5-second reclosing interval (the line has no current at this moment) after monitoring an instantaneous fault current. At this time, the monitoring and control terminals ZD3, ZS1, ZS4, and ZS5 report to the host MA that a momentary fault has occurred on the line. If a permanent phase-to-phase short-circuit fault occurs at the d1 fault point, the switch D3 in the substation will fail to close after the first disconnection. After the monitoring and control terminals ZD3, ZS1, ZS4, ZS5 detect an instantaneous fault current, after a reclosing time of 0.5 seconds, the monitoring and control terminals ZD3, ZS1, ZS4, and ZS5 will monitor an instantaneous fault current again, and then , the switch D3 in the substation will be disconnected again. At this time, the monitoring control terminals ZD3, ZS1, ZS4, and ZS5 report to the host MA that a permanent fault has occurred on the line, and the fault current has passed through the switches D3, S1, S4, and S5. . The display screen of the host MA shows the path of the short-circuit current, and on the computer screen, the computer automatically marks the switches D3, S1, S4, and S5 that the short-circuit current passes through. At this time, the host MA notifies the relevant staff of the faulty section information through computer screen display, sound and light alarm and mobile phone short message. Accordingly, the personnel on duty will click and control the disconnection switch S5 by the computer mouse, and cut off the faulty branch line 5 . At this time, the computer system can also be set to automatically perform disconnection of the switch S5. After S5 is disconnected, the staff will notify the substation operator to close the switch D3 in the substation according to the fault isolation prompt on the computer screen, so that the fault-free section of the line can resume power transmission in the shortest possible time.

The internal interconnection and working process between the monitoring control terminal and the host computer are shown in Figure 2. In the working block diagram of the monitoring control terminal and the host computer shown in Figure 2, a single-phase grounding or phase-to-phase short circuit occurs in the distribution system where the neutral point is not directly grounded In case of failure, the monitoring and control part of the monitoring and control terminal collects zero-sequence current or phase-to-phase short-circuit current data from the built-in current transformer of the substation outlet switch or the switch on the line column (or ring network cabinet switch), and then passes the data through GPRS/ GSM wireless communication (or other wired communication) is sent to the host, and the host analyzes and judges the specific location of the fault, and then sends the monitoring and control terminal to disconnect the substation outlet switch through GPRS/GSM wireless communication (or other wired communication) Or the command of the switch on the line column (or the switch of the ring network cabinet), so as to realize the purpose of cutting and isolating the fault and restoring the power supply of the fault-free section.

In Figure 2, each monitoring and control terminal uses its own built-in GPS satellite timing synchronous clock to mark the collected transient and steady-state zero-sequence current data with precise time stamps for the host to use as the zero-sequence data collected by each monitoring and control terminal. It is used when sequence current is compared with amplitude and phase.

In order to illustrate the realization of the present utility model, the above-mentioned specific embodiments have been described, but other changes and modifications of the present utility model are obvious to those skilled in the art. Amendments/changes or equivalent transformations all belong to the protection scope of the claims of the present utility model.

Claims (1)

1. neutral nondirect earthing network single-phase earth fault positioning device, comprise main frame (MA), Monitoring and Controlling terminal (ZD), it is characterized in that: each Monitoring and Controlling terminal (ZD) is installed on the distribution line on-pole switch or ring main unit switch (S) is located, and each Monitoring and Controlling terminal (ZD) is synchronous by gps satellite time service synchronised clock inhibit signal acquisition time.

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