Protection device for preventing line protection from malfunction caused by tripping off of bus PT air switch

Abstract

The invention relates to a protection device for preventing line protection from malfunction caused by tripping of a bus PT air switch, and the device comprises a bus voltage sampling unit which is used for collecting a bus voltage signal; the PT air switch state monitoring module is used for detecting the opening and closing state of a bus PT air switch in real time; the logic judgment module is used for carrying out voltage disappearance reason logic judgment by combining the bus voltage signal, the air switch state signal and the line current signal, and generating a latch-up protection action signal when judging that the voltage disappearance is caused by tripping of the bus PT air switch; the protection action output unit is used for outputting a protection action or a locking protection action according to the logic judgment result of the logic judgment module; and the alarm unit is used for giving an alarm prompt when the bus PT air switch is in a tripping state. The protection device can effectively prevent line protection misoperation caused by tripping of the bus PT air switch, and the reliability of a protection system is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of relay protection and control in power systems, and particularly relates to a protection device for preventing line protection from malfunctioning due to the tripping of the bus PT air switch. Background Art

[0002] During the operation of a power system, the bus voltage transformer (PT) usually provides key voltage signals for relay protection devices. If the secondary circuit switch of the bus voltage transformer (i.e., the "air switch") trips or is accidentally disconnected due to reasons, the protection device may misjudge that a line fault has occurred due to the loss of the correct voltage signal, resulting in a malfunction of the protection. Such faults may cause unnecessary power outages and affect the stability and power supply reliability of the power system.

[0003] Existing technologies usually adopt a low-voltage blocking function to prevent malfunctions, but when the bus PT air switch trips, the line protection may still malfunction because it cannot distinguish between the interruption of the voltage source and an actual line fault. Therefore, a more reliable anti-malfunction design is needed. Summary of the Invention

[0004] The purpose of the present invention is to provide a protection device for preventing line protection from malfunctioning due to the tripping of the bus PT air switch. This protection device can effectively prevent the malfunction of line protection caused by the tripping of the bus PT air switch and improve the reliability of the protection system.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is: a protection device for preventing line protection from malfunctioning due to the tripping of the bus PT air switch, comprising: A bus voltage sampling unit for collecting bus voltage signals; A PT air switch status monitoring module for real-time detecting the opening and closing status of the bus PT air switch; A logic judgment module for combining the bus voltage signal, the air switch status signal, and the line current signal to perform a logical judgment on the cause of voltage disappearance, and generating a blocking protection action signal when it is judged that the voltage disappearance is caused by the tripping of the bus PT air switch; A protection action output unit for outputting a protection action or blocking a protection action according to the logical judgment result of the logic judgment module; An alarm unit for giving an alarm prompt when the bus PT air switch is in the tripped state.

[0006] Further, the logic judgment module combines the bus voltage signal, the air switch status signal, and the line current signal to perform a logical judgment on the cause of voltage disappearance, and judges whether the disappearance of the bus voltage is caused by a line fault or the tripping of the bus PT air switch: When the protection device detects the disappearance of the bus voltage, if the bus PT air switch is in the closed state and the line current fluctuates, it is determined that there is an actual line fault. At this time, an output protection action signal is generated, and a blocking protection action signal is not generated; When the protection device detects the disappearance of the bus voltage, if the bus PT air switch is in the tripped state and there is no current fluctuation in the line, it is determined that the disappearance of the voltage is caused by the tripping of the bus PT air switch. At this time, a blocking protection action signal is generated; When the protection device detects the disappearance of the bus voltage, if the bus PT air switch is in the tripped state and the line current fluctuates, it is determined that there is an actual line fault. At this time, an output protection action signal is generated, and a blocking protection action signal is not generated.

[0007] Further, the PT air switch status monitoring module includes a normally closed auxiliary node module and a normally open auxiliary node module. The operating handles of the normally closed auxiliary node module and the normally open auxiliary node module are connected and linked to the operating handle of the bus PT air switch through a connecting rod; when the PT air switch is in the conducting state, the normally closed auxiliary node module is disconnected, and the normally open auxiliary node module is closed. When the PT air switch is in the tripped state, the normally closed auxiliary node module is closed, and the normally open auxiliary node module is disconnected; the normally closed auxiliary node module is connected to the line measurement and control device, and the normally open auxiliary node module is connected to the backup protection circuit.

[0008] Further, one end of the normally closed auxiliary node module is connected to the signal common terminal of the line measurement and control device, and the other end is connected to the negative pole of the signal power supply of the line measurement and control device, thereby forming an alarm circuit for the tripping of the bus PT air switch; When the line is operating normally, the bus PT air switch is closed, the normally closed auxiliary node module is disconnected, and the line measurement and control device will not send out the signal of "the bus PT air switch trips"; when the line has an abnormality and the bus PT air switch trips, the normally closed auxiliary node module is closed, the alarm circuit for the tripping of the bus PT air switch is turned on, and the line measurement and control device sends out the signal of "the bus PT air switch trips" to the background.

[0009] Further, in the backup protection circuit, after the normally open auxiliary node module is connected in parallel with the normally open auxiliary node for starting the line protection, it is connected in series in the outlet circuit of the distance and zero-sequence backup protection to form a backup protection circuit for preventing the misoperation of the line protection; Under normal operating conditions of the line, the bus PT air switch is closed, the normally open auxiliary node module is closed, and the normally open auxiliary node for starting the line protection is disconnected. Since the normally open auxiliary node module and the normally open auxiliary node for starting the line protection are in an OR relationship, the backup protection circuit is turned on; If a line fault occurs and the line current fluctuates, both the normally open auxiliary node module and the normally open auxiliary node for starting the line protection are closed, and the line protection device can operate normally; If the bus PT air switch trips, causing the bus voltage of the line protection device to disappear, the normally open auxiliary node module disconnects, and there is no current fluctuation at the same time. The normally open auxiliary node for line protection startup disconnects. Since both the normally open auxiliary node module and the normally open auxiliary node for line protection startup are disconnected, the backup protection circuit is not conducting. The logic judgment module determines that the voltage disappearance is caused by the tripping of the bus PT air switch rather than a line fault, so the backup protection is blocked. If the normally open auxiliary node module fails and cannot correctly judge the air switch situation, and the normally open auxiliary node module is in a disconnected state for a long time, at this time, the normally open auxiliary node for line protection startup controls the on-off of the backup protection circuit, thereby preventing misoperation and refusal to operate of the line protection device.

[0010] Further, in the backup protection circuit, after the normally open auxiliary node module and the normally open auxiliary node for line protection startup are connected in parallel, one end of the parallel circuit is connected to the input common terminal of the line protection device, and the other end is simultaneously connected to the distance protection connection terminal and the zero-sequence protection connection terminal.

[0011] Further, the protection device has a self-checking function, regularly self-checks the operating state of the PT air switch status monitoring module, and gives an alarm prompt for abnormality when it is abnormal.

[0012] Further, the protection action output unit does not output a trip signal in the blocked state and preferentially sends an alarm message.

[0013] Further, if the line current signal is continuously abnormal or other relay protection startup signals are triggered, the blocking is released, and the line protection device resumes its normal function.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a protection device for preventing the misoperation of line protection due to the tripping of the bus PT air switch. Through the design of the PT air switch status monitoring module and the logic judgment module, this protection device can determine whether the disappearance of the bus voltage is caused by a line fault or the tripping of the bus PT air switch, and then output a protection action or block the protection action, effectively preventing the misoperation of line protection caused by the tripping of the bus PT air switch, ensuring that the line protection will not misoperate when losing the voltage signal, thereby improving the reliability of the protection system, being applicable to the relay protection devices of various power systems, and having significant practical value and popularization prospects. Description of the Drawings

[0015] Figure 1 is the implementation schematic diagram of the protection device for preventing the misoperation of line protection due to the tripping of the bus PT air switch in the embodiment of the present invention; Figure 2 is the structural schematic diagram of the PT air switch status monitoring module in the embodiment of the present invention. Detailed Embodiments

[0016] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0017] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs.

[0018] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0019] This embodiment provides a protection device for preventing the line protection from malfunctioning due to the tripping of the bus PT air switch, including: a bus voltage sampling unit, a PT air switch status monitoring module, a logic judgment module, a protection action output unit, and an alarm unit.

[0020] The bus voltage sampling unit is used to collect bus voltage signals and send them to the line protection device.

[0021] The PT air switch status monitoring module is used to detect the opening and closing status of the bus PT air switch in real time.

[0022] The logic judgment module is used to combine the bus voltage signal, the air switch status signal, and the line current signal to perform logical judgment on the cause of voltage disappearance, and generate a signal to block the protection action when it is judged that the voltage disappearance is caused by the tripping of the bus PT air switch.

[0023] The protection action output unit is used to output a protection action or block the protection action according to the logical judgment result of the logic judgment module.

[0024] The alarm unit is used to send an alarm prompt to the duty personnel when the bus PT air switch is in the tripped state (i.e., the blocked state).

[0025] Specifically, the logic judgment module combines the bus voltage signal, the air switch status signal, and the line current signal to perform logical judgment on the cause of voltage disappearance, and determines whether the bus voltage disappearance is caused by a line fault or by the tripping of the bus PT air switch: 1) When the protection device detects the disappearance of the bus voltage, if the bus PT air switch is in the closed state and the line current fluctuates, it is determined that there is an actual line fault. At this time, a signal to output a protection action is generated, and a signal to block the protection action is not generated; 2) When the protection device detects the disappearance of the bus voltage, if the bus PT air switch is in the tripped state and there is no current fluctuation in the line, it is determined that the voltage disappearance is caused by the tripping of the bus PT air switch. At this time, a signal to block the protection action is generated. 3) When the protection device detects the disappearance of the bus voltage, if the bus PT air switch is in the tripped state and there is current fluctuation in the line, it is determined that there is an actual line fault. At this time, a signal to output the protection action is generated, and a signal to block the protection action is not generated.

[0026] In this device, a PT air switch status monitoring module is added to the secondary air switch of the bus voltage transformer (PT) to detect the opening and closing status of the PT secondary air switch in real time. As Figure 1 、 2 shown, the PT air switch status monitoring module includes a normally closed auxiliary node module (7-8) and a normally open auxiliary node module (9-10). The operating handles of the normally closed auxiliary node module (7-8) and the normally open auxiliary node module (9-10) are connected and linked to the operating handle of the three-phase air switch of the bus PT (1-2, 3-4, 5-6) through link A and link B. Under normal circumstances, the operating handle is pushed up to the top, the PT air switch is in the conducting state, the normally closed auxiliary node module (7-8) is disconnected, and the normally open auxiliary node module (9-10) is closed. If an abnormality occurs in the bus, causing the air switch to trip, the operating handle is automatically pushed to the bottom, driving the operating handle of the PT air switch status monitoring module to be pushed down through link A and link B. At this time, the PT air switch is in the tripped state, the normally closed auxiliary node module (7-8) is closed, and the normally open auxiliary node module (9-10) is disconnected.

[0027] The normally closed auxiliary node module (7-8) is connected to the line measurement and control device, and the normally open auxiliary node module (9-10) is connected to the backup protection circuit. Specifically, one end of the normally closed auxiliary node module (7-8) is connected to the signal common terminal of the line measurement and control device, and the other end is connected to the negative pole of the signal power supply of the line measurement and control device, thus forming an alarm circuit for the tripping of the bus PT air switch (i.e., the alarm circuit for blocking the backup protection).

[0028] When the line is operating normally, the bus PT air switch is closed, the normally closed auxiliary node module (7-8) is disconnected, and the line measurement and control device will not send out the signal of "tripping of the bus PT air switch" (i.e., the signal of "blocking the backup protection"). When an abnormality occurs in the line and the bus PT air switch trips, the normally closed auxiliary node module (7-8) is closed, the alarm circuit for the tripping of the bus PT air switch is conducted, and the line measurement and control device sends out the signal of "tripping of the bus PT air switch" (i.e., the signal of "blocking the backup protection") to the background.

[0029] In the backup protection circuit, after the normally open auxiliary node module (9-10) is connected in parallel with the normally open auxiliary node for line protection startup, it is connected in series in the outlet circuit of the distance and zero-sequence backup protection to form a backup protection circuit to prevent misoperation of the line protection. Specifically, after the normally open auxiliary node module (9-10) is connected in parallel with the normally open auxiliary node for line protection startup, one end of the parallel circuit is connected to the common input terminal of the line protection device, and the other end is simultaneously connected to the connection terminal of the distance protection and the connection terminal of the zero-sequence protection. The control method of the protection device is as follows.

[0030] Under normal operation of the line, the bus PT air switch is closed, the normally open auxiliary node module (9-10) is closed, and the normally open auxiliary node for line protection startup is open. Since the normally open auxiliary node module (9-10) and the normally open auxiliary node for line protection startup are in an "OR" relationship, the backup protection circuit is conducting.

[0031] If a line fault occurs and the line current fluctuates, both the normally open auxiliary node module (9-10) and the normally open auxiliary node for line protection startup are closed, and the line protection device can operate normally.

[0032] If the bus PT air switch trips, causing the bus voltage of the line protection device to disappear, the normally open auxiliary node module (9-10) opens, and there is no current fluctuation at the same time. The normally open auxiliary node for line protection startup opens. Since both the normally open auxiliary node module (9-10) and the normally open auxiliary node for line protection startup are open, the backup protection circuit is not conducting. The logic judgment module determines that the voltage disappearance is caused by the tripping of the bus PT air switch, rather than a line fault, so the backup protection (distance protection or zero-sequence protection) is blocked.

[0033] If the normally open auxiliary node module (9-10) fails and cannot correctly judge the air switch situation, the normally open auxiliary node module (9-10) is in an open state for a long time. At this time, the normally open auxiliary node for line protection startup controls the on-off of the backup protection circuit, thus preventing misoperation and refusal to operate of the line protection device.

[0034] The protection action output unit does not output a tripping signal in the blocked state and preferentially sends an alarm message.

[0035] Fault state release: If the line current signal remains abnormal or other relay protection startup signals are triggered, the block is released, and the line protection device resumes normal function.

[0036] Self-check function: The protection device has a self-check function, regularly self-checks the operating state of the PT air switch status monitoring module, and gives an alarm prompt for abnormality when it is abnormal.

[0037] Embodiment 1: Handling of the disappearance of the bus voltage caused by the tripping of the PT air switch During the operation of a certain substation, due to an operation error, the bus PT air switch 1ZKK tripped. The line protection device detected the disappearance of the bus voltage signal. At the same time, the normally closed auxiliary node module (7-8) of the PT air switch closed, and the background reported the signal of "bus PT air switch tripped". At this time, there was no fluctuation in the secondary current of the line, the normally open auxiliary node for starting the line protection did not close, the normally open auxiliary node module (9-10) of the air switch was disconnected, and the backup protection circuit after two "OR" logics was in a disconnected state. At this time, the input circuit of the backup protection function pressure plate (distance protection CLP1, zero-sequence protection CLP2) was cut off, and the differential protection CLP3 did not need to judge the voltage and was not affected by this. Through comprehensive analysis, it was confirmed that the voltage disappearance was caused by the PT air switch. The input of the backup function pressure plate of the line protection was blocked and an alarm was issued, avoiding the misoperation of the line protection.

[0038] Embodiment 2: Handling of actual line faults A single-phase grounding fault occurred on the line, the bus voltage dropped significantly, and the PT air switch status monitoring module did not issue the signal of "bus PT air switch tripped". The logic judgment module determined it as an actual line fault and immediately output a protection action to cut off the faulty line.

[0039] Embodiment 3: The PT air switch tripped while a line fault occurred During the operation of a certain substation, due to human operation, the bus PT air switch 1ZKK tripped. The line protection device detected the disappearance of the bus voltage signal. At the same time, the normally closed auxiliary node module (7-8) of the PT air switch closed, and the background reported the signal of "bus PT air switch tripped". At this time, due to the line fault, the secondary current fluctuated, the normally open auxiliary node for starting the line protection closed, the normally open auxiliary node module (9-10) of the air switch was disconnected, and the backup protection circuit after two "OR" logics was in a conducting state. At this time, the backup protection function pressure plate (distance protection CLP1, zero-sequence protection CLP2) was normally put into operation, determined as an actual line fault, and immediately output a protection action to cut off the faulty line.

[0040] The above are only the preferred embodiments of the present invention, and are not limitations to the present invention in other forms. Any person skilled in the art may use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still belong to the protection scope of the technical solution of the present invention.

Claims

1. A protection device for preventing line protection from malfunctioning due to busbar PT circuit breaker tripping, characterized in that: include: A bus voltage sampling unit, used for collecting bus voltage signals; PT circuit breaker status monitoring module, used to detect the opening and closing status of the busbar PT circuit breaker in real time; The logic judgment module is used to combine the bus voltage signal, the circuit breaker status signal and the line current signal to perform a logic judgment on the cause of voltage disappearance, and generate a locking protection action signal when it is judged that the voltage disappearance is caused by the bus PT circuit breaker tripping; A protection action output unit is used to output a protection action or a blocking protection action according to the logic judgment result of the logic judgment module; The alarm unit is used to issue an alarm when the busbar PT circuit breaker is tripped.

2. The protection device for preventing line protection from malfunctioning due to busbar PT circuit breaker tripping according to claim 1 is characterized in that: The logic judgment module combines the bus voltage signal, the circuit breaker status signal and the line current signal to perform a logic judgment on the cause of the voltage disappearance, and determines whether the bus voltage disappearance is caused by a line fault or a bus PT circuit breaker tripping: When the protection device detects that the bus voltage disappears, if the bus PT circuit breaker is in the closed state and the line current fluctuates, it is determined to be an actual line fault. At this time, an output protection action signal is generated instead of a blocking protection action signal; When the protection device detects that the bus voltage disappears, if the bus PT circuit breaker is in the tripped state and there is no current fluctuation in the line, it is determined that the voltage disappearance is caused by the bus PT circuit breaker tripping, and a blocking protection action signal is generated at this time; When the protection device detects that the bus voltage disappears, if the bus PT circuit breaker is in the tripped state and there is fluctuation in the line current, it is determined to be an actual line fault. At this time, an output protection action signal is generated instead of a lockout protection action signal.

3. The protection device for preventing line protection from malfunctioning due to busbar PT circuit breaker tripping according to claim 1 is characterized in that: The PT circuit breaker status monitoring module includes a normally closed auxiliary node module and a normally open auxiliary node module. The operating handles of the normally closed auxiliary node module and the normally open auxiliary node module are connected and linked to the operating handle of the bus PT circuit breaker through a connecting rod; when the PT circuit breaker is in the on state, the normally closed auxiliary node module is disconnected and the normally open auxiliary node module is closed, and when the PT circuit breaker is in the tripped state, the normally closed auxiliary node module is closed and the normally open auxiliary node module is disconnected; the normally closed auxiliary node module is connected to the line measurement and control device, and the normally open auxiliary node module is connected to the backup protection circuit.

4. The protection device for preventing line protection from malfunctioning due to busbar PT circuit breaker tripping according to claim 3 is characterized in that: One end of the normally closed auxiliary node module is connected to the signal common end of the line measurement and control device, and the other end is connected to the negative electrode of the signal power supply of the line measurement and control device, thereby forming a bus PT circuit breaker trip alarm circuit; When the line operates normally, the bus PT circuit breaker is closed, the normally closed auxiliary node module is disconnected, and the line measurement and control device will not send out a "bus PT circuit breaker tripped" signal; when an abnormality occurs in the line and the bus PT circuit breaker trips, the normally closed auxiliary node module is closed, the bus PT circuit breaker tripping alarm circuit is connected, and the line measurement and control device sends out a "bus PT circuit breaker tripped" signal to the background.

5. The protection device for preventing line protection from malfunctioning due to busbar PT circuit breaker tripping according to claim 3 is characterized in that: In the backup protection circuit, the normally open auxiliary node module is connected in parallel with the normally open auxiliary node of the line protection start-up, and then connected in series in the outlet circuit of the distance and zero-sequence backup protection to form a backup protection circuit to prevent the line protection from malfunctioning; When the line is operating normally, the busbar PT circuit breaker is closed, the normally open auxiliary node module is closed, and the line protection start normally open auxiliary node is disconnected. Since the normally open auxiliary node module and the line protection start normally open auxiliary node are in an OR relationship, the backup protection circuit is turned on. If a line fault occurs and the line current fluctuates, the normally open auxiliary node module and the line protection start normally open auxiliary node are both closed, and the line protection device can operate normally; If the bus PT circuit breaker trips, causing the bus voltage of the line protection device to disappear, the normally open auxiliary node module is disconnected, and there is no current fluctuation, the line protection start normally open auxiliary node is disconnected, and since both the normally open auxiliary node module and the line protection start normally open auxiliary node are disconnected, the backup protection circuit is not conductive, and the logic judgment module determines that the voltage disappearance is caused by the bus PT circuit breaker tripping, rather than the line fault, and thus the backup protection is locked; If the normally open auxiliary node module fails and cannot correctly judge the circuit breaker situation, the normally open auxiliary node module will be in the disconnected state for a long time. At this time, the line protection will start the normally open auxiliary node to control the on and off of the backup protection circuit, thereby preventing the line protection device from malfunctioning or refusing to operate.

6. The protection device for preventing line protection from malfunctioning due to busbar PT circuit breaker tripping according to claim 5, characterized in that: In the backup protection circuit, after the normally open auxiliary node module is connected in parallel with the line protection start normally open auxiliary node, one end of the parallel circuit is connected to the open common terminal of the line protection device, and the other end is simultaneously connected to the distance protection connection terminal and the zero-sequence protection connection terminal.

7. The protection device for preventing line protection from malfunctioning due to busbar PT circuit breaker tripping according to claim 1, characterized in that: The protection device has a self-checking function, regularly performs self-checking on the operating status of the PT circuit breaker status monitoring module, and alarms when it is abnormal.

8. The protection device for preventing line protection from malfunctioning due to busbar PT circuit breaker tripping according to claim 1, characterized in that: The protection action output unit does not output a trip signal in a locked state, and gives priority to sending an alarm message.

9. The protection device for preventing line protection from malfunctioning due to busbar PT circuit breaker tripping according to claim 1, characterized in that: If the line current signal continues to be abnormal or other relay protection start signals are triggered, the lockout is released and the line protection device resumes normal function.

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