A double-coil open-phase phase sequence protection relay and double power switching system

Abstract

This invention discloses a dual-coil phase loss and phase sequence protection relay and a dual-power supply switching system. The dual-coil phase loss and phase sequence protection relay outputs two pairs of passive contacts. One pair of passive contacts is the operating contact, used for outputting a three-phase power supply monitoring result signal. The other pair of passive contacts is the fault contact, used for outputting a self-diagnostic alarm signal. Both the operating contact and the fault contact are controlled and switched by independent coils. This solves the problem that in existing phase loss and phase sequence protection relays, the operating contact and fault contact share the same coil. When no phase loss or phase failure occurs in the actual power supply, the relay's own malfunction causes the PLC to detect a power fault and fail to execute the power switching command, thus affecting dual-power supply switching.

Description

Technical Field

[0001] This invention relates to the field of relay technology, and in particular to a dual-coil phase loss sequence protection relay and a dual power supply switching system. Background Technology

[0002] The cooling control system of a forced oil circulation air-cooled transformer plays a crucial role in the safe and stable operation of the transformer. To ensure the normal operation of the cooling system, a dual power supply method is adopted. As a key link in the primary power supply circuit, the reliability of the dual power supply automatic switching unit directly affects the safe operation of the transformer.

[0003] To achieve automatic switching between dual power supplies, it is necessary to automatically measure and judge the power supply status, and then execute the switching operation. Currently, the common practice for power supply monitoring is to use dedicated phase loss and phase sequence protection relays, and to complete the switching between them in the loop control based on the collected judgment results.

[0004] Currently, the operating contacts and fault contacts of the phase loss and phase sequence protection relays are the same coil. When the phase loss and phase sequence protection relays themselves fail, the PLC mistakenly detects a power supply fault, resulting in the inability to execute the power switching command. However, the actual power supply has not experienced a phase loss or phase interruption fault. Therefore, the failure of the phase loss and phase sequence protection relays themselves directly affects the power switching. If both phase loss and phase sequence protection relays fail, both power supplies will be shut down, causing the air cooling system to stop completely, which seriously affects the reliable operation of the transformer. Summary of the Invention

[0005] The purpose of this invention is to provide a dual-coil phase loss and phase sequence protection relay and a dual power supply switching system, which can solve the problem that the power supply switching function is affected when existing phase loss and phase sequence protection relays fail.

[0006] According to an embodiment of the present invention, in a first aspect, a dual-coil phase-sequence loss protection relay is provided, comprising a PLC, an actuating contact relay, a monitoring module, and a fault contact relay. The PLC is electrically connected to an external three-phase power supply and monitors the three-phase power supply status, which includes a normal state or an abnormal state. The actuating contact relay outputs a pair of passive contacts as the actuating contacts. The actuating contact relay is electrically connected to the PLC. The PLC sends coil commands to the actuating contact relay according to the received three-phase power supply status signals to control the actuating contacts of the actuating contact relay to open or close. The monitoring module is electrically connected to the PLC and is used to monitor the operating status of the PLC, which includes a normal state or a fault state. The fault contact relay outputs a pair of passive contacts as the fault contacts. The fault contact relay is electrically connected to the monitoring module. When the monitoring module detects that the PLC is in a fault state, the monitoring module controls the fault contacts of the fault contact relay to open or close.

[0007] In some embodiments, when the PLC detects that the three-phase power supply is in a normal state, the PLC controls the action contact relay to open; when the PLC detects that the three-phase power supply is in an abnormal state, the PLC controls the action contact relay to close; when the monitoring module detects that the PLC is in a normal operating state, the monitoring module controls the fault contact relay to open; when the monitoring module detects that the PLC is in a fault operating state, the monitoring module controls the fault contact relay to close.

[0008] In some embodiments, the phase loss sequence protection relay further includes a voltage module, the voltage module having a 3000kV isolation level, the voltage module being electrically connected to the microprocessor, and the voltage module supplying power to the microprocessor.

[0009] In some embodiments, the phase loss and phase sequence protection relay further includes a display module, which is electrically connected to the PLC. The display module is used to display the three-phase power supply status monitored by the PLC. The display module is also electrically connected to the monitoring module, which is used to display the PLC operating status monitored by the monitoring module. The display module includes a phase reversal indicator, a phase loss indicator, a fault indicator, and a running indicator. The phase reversal indicator, phase loss indicator, fault indicator, and running indicator are all electrically connected to the PLC. The phase reversal indicator and phase loss indicator are used to display the three-phase power supply status, and the fault indicator and running indicator are used to display the PLC operating status.

[0010] In some embodiments, the phase loss sequence protection relay further includes a measurement and control module, which is electrically connected to the PLC and the monitoring module respectively. The measurement and control module acquires the three-phase power supply status and the PLC operating status, and sends signals and alarms to the background terminal.

[0011] Secondly, a dual power supply switching system is provided. The dual power supply switching system is used to switch between two three-phase power supplies that supply power to the same load. The two three-phase power supplies are a first power supply and a second power supply. The dual power supply switching system includes a dual-coil phase loss sequence protection relay and contactors. There are two dual-coil phase loss sequence protection relays, namely QX1 and QX2. QX1 and QX2 monitor the power status of the first power supply and the second power supply, respectively. There are two contactors, namely KM1 and KM2. The first power supply, KM1 and the load constitute a first circuit, and the second power supply, KM2 and the load constitute a second circuit.

[0012] Both the action contact and fault contact of QX1 are electrically connected to KM1. When the PLC of QX1 is in normal operating state, the fault contact of QX1 is open, and the PLC controls the action contact relay to operate, thereby controlling KM1 to close or open. When the PLC of QX1 is in fault operating state, the monitoring module controls the fault contact relay to operate, thereby controlling KM1 to close or open. Both the action contact and fault contact of QX2 are electrically connected to KM2, and QX2 controls KM2 to close or open.

[0013] As can be seen from the above technical solution, the present invention provides a dual-coil phase-loss sequence protection relay and a dual-power supply switching system. The dual-coil phase-loss sequence protection relay outputs two pairs of passive contacts. One pair of passive contacts is the operating contact, used for outputting the three-phase power supply monitoring result signal. The other pair of passive contacts is the fault contact, used for outputting the self-diagnostic alarm signal. Both the operating contact and the fault contact are controlled and switched by independent coils. When the dual-coil phase-loss sequence protection relay is normal, the PLC sends a coil command to the operating contact relay according to the monitored three-phase power supply status signal to control the operating contact. When the relay's operating contacts activate, it executes the power switching command. When the dual-coil phase loss and phase sequence protection relay malfunctions, the monitoring module detects the PLC malfunction and sends a coil command to the faulty contact relay, controlling the faulty contact relay to activate and execute the power switching command. This solves the problem that in existing phase loss and phase sequence protection relays, the operating contacts and faulty contacts are the same coil. When there is no actual phase loss or phase failure in the power supply, the PLC detects a power failure due to the fault of the phase loss and phase sequence protection relay itself, and is unable to execute the power switching command, thus affecting the dual power supply switching. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a structural block diagram of a dual-coil phase-sequence loss protection relay provided in an embodiment of the present invention;

[0016] Figure 2 A structural block diagram of the display module of the dual-coil phase-sequence loss protection relay provided in an embodiment of the present invention;

[0017] Figure 3 This is a wiring diagram of a dual-coil phase-sequence loss protection relay provided in an embodiment of the present invention;

[0018] Figure 4 A circuit diagram of a dual-coil phase-sequence loss protection relay provided in an embodiment of the present invention;

[0019] Figure 5 This is a hardware connection diagram of a dual power supply switching system provided in an embodiment of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Please see Figure 3 As shown, this embodiment of the invention provides a dual-coil phase loss sequence protection relay. The dual-coil phase loss sequence protection relay is used to monitor three-phase power supply and protect the load. The dual-coil phase loss sequence protection relay outputs two pairs of passive contacts. One pair of passive contacts is the operating contact, which is used for outputting the three-phase power supply monitoring result signal. The other pair of passive contacts is the fault contact, which is used for outputting the self-diagnostic alarm signal. That is, the output of the three-phase power supply monitoring result signal and the output of the self-diagnostic alarm signal do not affect each other. The contact capacity of both the operating contact relay and the fault contact relay can be AC250V.

[0022] Please see Figure 1 As shown, in some embodiments, the dual-coil phase loss sequence protection relay includes a PLC, an operating contact relay, a monitoring module, and a fault contact relay.

[0023] The PLC includes a microprocessor, which uses an STM32F103CBT6 32-bit ARM microprocessor. The microprocessor is electrically connected to an external three-phase power supply through three contacts to monitor the status of the three-phase power supply. The three-phase power supply status is measured as either normal or abnormal. When overvoltage, undervoltage, phase loss, or phase sequence reversal is detected in the three-phase power supply, it is determined to be in an abnormal state; otherwise, it is determined to be in a normal state.

[0024] The pair of passive contacts output by the action contact relay are the action contacts. The action contact relay is electrically connected to the PLC. The PLC sends coil commands to the action contact relay according to the monitored three-phase power status signals, controls the action contacts of the action contact relay to act, and then executes the power switching command.

[0025] The monitoring module is electrically connected to the PLC and monitors the operating status of the PLC, including normal or fault status.

[0026] The pair of passive contacts output by the fault contact relay are the fault contacts. The fault contact relay is electrically connected to the monitoring module. When the monitoring module detects that the PLC is in a fault state, the monitoring module sends a coil command to the fault contact relay according to the received three-phase power status signal, controls the fault contact action of the fault contact relay, and then executes the power switching command.

[0027] When the PLC detects that the three-phase power supply is in a normal state, the PLC controls the action contact relay to open. When the PLC detects that the three-phase power supply is in an abnormal state, the PLC controls the action contact relay to close. When the monitoring module detects that the PLC is in a normal operating state, the monitoring module controls the fault contact relay to open. When the monitoring module detects that the PLC is in a fault operating state, the monitoring module controls the fault contact relay to close.

[0028] The dual-coil phase-loss sequence protection relay disclosed in this application is applicable to the following three situations:

[0029] 1. When the three-phase power supply is in normal condition, the PLC is also in normal condition:

[0030] The PLC monitors the three-phase power supply status. If there is no overvoltage, undervoltage, phase loss, or phase sequence reversal in the three-phase power supply, it is determined that the three-phase power supply is in a normal state. If the monitoring module detects that the PLC is in a normal state, the monitoring module controls the fault contact relay to open the fault contact relay, that is, the fault contact relay does not work. The PLC sends a coil command to the action contact relay to control the action contact relay to close the action contact relay, thereby controlling the power supply of the three-phase power main circuit.

[0031] 2. When the three-phase power supply is in an abnormal state, the PLC is in a normal state:

[0032] The PLC monitors the three-phase power supply status. If the three-phase power supply has overvoltage, undervoltage, phase loss, or phase sequence reversal, it is determined that the three-phase power supply is in an abnormal state. If the monitoring module detects that the PLC is in a normal state, the monitoring module controls the fault contact relay to open the fault contact, that is, the fault contact relay does not work. The PLC receives the three-phase power supply abnormal state signal sent by the microprocessor and sends a coil command to the action contact relay to control the action contact relay to open the action contact, thereby controlling the power outage of the three-phase power supply main circuit.

[0033] 3. When the PLC is in a fault state:

[0034] When the PLC is in a fault state, the action contact relay cannot execute the power switching command. If the monitoring module detects that the PLC is in a fault state, it will send a coil command to the fault contact relay to control the fault contact relay to close, thereby controlling the power supply of the three-phase power main circuit.

[0035] Please see Figure 1 As shown, in some embodiments, the dual-coil phase loss sequence protection relay further includes a voltage module with a 3000kV isolation level. The voltage module is electrically connected to the microprocessor and supplies power to the microprocessor.

[0036] Please see Figure 2 As shown, in some embodiments, the dual-coil phase loss sequence protection relay further includes a display module. The display module is electrically connected to the microprocessor and is used to display the three-phase power supply status monitored by the microprocessor. The display module is also electrically connected to the monitoring module and is used to display the PLC operating status monitored by the monitoring module. The display module includes a phase reversal indicator, a phase loss indicator, a fault indicator, and a running indicator. The phase reversal indicator, phase loss indicator, fault indicator, and running indicator are all electrically connected to the PLC. The phase reversal indicator and phase loss indicator are used to display the three-phase power supply status, and the fault indicator and running indicator are used to display the PLC operating status. The phase reversal indicator, phase loss indicator, and fault indicator are all red lights, and the running indicator is a green light, which facilitates the display of alarms.

[0037] In some embodiments, the dual-coil phase-loss sequence protection relay further includes a measurement and control module, which is electrically connected to the PLC and the monitoring module respectively. The measurement and control module acquires the three-phase power supply status and the PLC operating status, and sends signals and alarms to the background terminal so as to promptly repair or replace the faulty dual-coil phase-loss sequence protection relay, thereby avoiding damage to the load (three-phase motor).

[0038] In some embodiments, the dual-coil phase loss sequence protection relay further includes a rectification, filtering and voltage regulation module. The rectification, filtering and voltage regulation module consists of a transformer, a circular stack, an integrated voltage regulator, a capacitor and a resistor. The external three-phase power supply, the rectification, filtering and voltage regulation module and the microprocessor are electrically connected in sequence.

[0039] Please see Figure 4 The diagram shows the circuit diagram of a dual-coil phase-loss sequence protection relay. The central area is the processor, the upper right corner is the operating contact relay, the lower area contains the monitoring module and fault contact relay, and the upper left corner is the three-phase power monitoring circuit. This circuit connects to an external three-phase power supply via contacts L1, L2, and L3 to monitor the external three-phase power supply. When the PLC for the dual-coil phase-loss sequence protection relay is in normal operation, it receives the three-phase power supply status signal and sends coil commands to the operating contact relay, controlling the relay's operating contacts to open or close. The system closes the circuit, thereby controlling the on / off state of the main circuit of the three-phase power supply. If the PLC of the dual-coil phase loss and phase sequence protection relay malfunctions, the monitoring module sends a coil command to the fault contact relay to control the fault contact relay to close, thereby controlling the connection of the main circuit of the three-phase power supply. This solves the problem that the operating contact and fault contact of the existing phase loss and phase sequence protection relays are the same coil. When there is no phase loss or phase failure in the actual power supply, the PLC detects a power failure due to the fault of the phase loss and phase sequence protection relays themselves, and cannot execute the power switching command, thus affecting the dual power supply switching.

[0040] Please see Figure 5 As shown, this embodiment of the invention provides a dual power supply switching system, which is used to switch between two three-phase power supplies that supply power to the same load. The two three-phase power supplies are a first power supply and a second power supply. The dual power supply switching system includes a dual-coil phase loss sequence protection relay and a contactor.

[0041] The dual-coil phase loss sequence protection relay has two components, namely QX1 and QX2. QX1 and QX2 monitor the power status of the first power supply and the second power supply, respectively. The contactor has two components, namely KM1 and KM2. The first power supply, KM1 and the load constitute the first circuit, and the second power supply, KM2 and the load constitute the second circuit.

[0042] Both the operating and fault contacts of QX1 are electrically connected to KM1. When the PLC of QX1 is in normal operation, the fault contact of QX1 is open, and the PLC controls the operating contact relay to activate, thereby controlling KM1 to close or open. When the PLC of QX1 is in fault operation, the monitoring module controls the fault contact relay to activate, thereby controlling KM1 to close. Both the operating and fault contacts of QX2 are electrically connected to KM2, and QX2 controls KM2 to close or open. Through the cooperation of QX1 and QX2, KM1 and KM2 are controlled to alternately close or open, thereby controlling the switching of dual power supplies.

[0043] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0044] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A two-coil open-phase phase sequence protection relay, characterized by: include: The PLC is electrically connected to an external three-phase power supply and monitors the status of the three-phase power supply, including normal or abnormal status. An actuating contact relay, wherein the pair of passive contacts output by the actuating contact relay are actuating contacts, the actuating contact relay is electrically connected to the PLC, and the PLC sends coil commands to the actuating contact relay according to the monitored three-phase power supply status signal to control the actuating contacts of the actuating contact relay to actuate. A monitoring module is electrically connected to the PLC and is used to monitor the operating status of the PLC, including normal status or fault status. The fault contact relay outputs a pair of passive contacts as fault contacts. The fault contact relay is electrically connected to the monitoring module. When the monitoring module detects that the PLC is in a fault state, the monitoring module sends a coil command to the fault contact relay to control the fault contact relay to operate. When the PLC detects that the three-phase power supply is in a normal state, the PLC controls the action contact relay to open. When the PLC detects that the three-phase power supply is in an abnormal state, the PLC controls the action contact relay to close. When the monitoring module detects that the PLC is in a normal operating state, the monitoring module controls the fault contact of the fault contact relay to be an open contact. When the monitoring module detects that the PLC is in a fault operating state, the monitoring module controls the fault contact of the fault contact relay to be a closed contact.

2. The dual-coil phase-sequence loss protection relay according to claim 1, characterized in that: The contact capacity of both the operating contact relay and the fault contact relay is AC250V.

3. The two-coil open-phase phase sequence relay according to claim 1, characterized in that, The phase loss sequence protection relay also includes: A voltage module, which is electrically connected to the microprocessor, supplies power to the microprocessor.

4. The dual-coil phase-sequence loss protection relay according to claim 3, characterized in that: The voltage module has a 3000kV isolation level.

5. The two-coil open-phase phase sequence relay according to claim 1, characterized in that, The phase loss sequence protection relay also includes a display module: The display module is electrically connected to the PLC, and the display module is used to display the three-phase power supply status monitored by the PLC; The display module is electrically connected to the monitoring module, and the display module is used to display the PLC operating status monitored by the monitoring module.

6. The dual-coil phase-sequence loss protection relay according to claim 5, characterized in that: The display module includes an inverted phase indicator, a phase loss indicator, a fault indicator, and a running indicator, all of which are electrically connected to the PLC. The phase reversal indicator and phase loss indicator are used to display the three-phase power supply status; The fault indicator and the running indicator are used to display the PLC's operating status.

7. The two-coil open-phase phase sequence relay according to claim 1, characterized in that, The phase loss sequence protection relay also includes: The measurement and control module is electrically connected to the PLC and the monitoring module respectively. The measurement and control module acquires the three-phase power supply status and the PLC operating status, and sends signals and alarms to the background terminal.

8. The dual-coil phase-sequence loss protection relay according to claim 1, characterized in that, The PLC includes a microprocessor, which is electrically connected to an external three-phase power supply for monitoring the status of the three-phase power supply.

9. A dual power supply switching system, the dual power supply switching system being used to switch between two three-phase power supplies supplying power to the same load, the two three-phase power supplies being a first power supply and a second power supply, the dual power supply switching system comprising: The dual-coil phase-loss phase sequence protection relay according to any one of claims 1-8, wherein the dual-coil phase-loss phase sequence protection relay is provided in two forms, namely QX1 and QX2, wherein QX1 and QX2 respectively monitor the power status of the first power supply and the second power supply. The contactor is provided in two parts, namely KM1 and KM2. The first power supply, KM1 and the load form a first circuit, and the second power supply, KM2 and the load form a second circuit. Both the action contact and the fault contact of QX1 are electrically connected to KM1. When the PLC of QX1 is in normal operating state, the fault contact of QX1 is an open contact, and the PLC controls the action contact relay to operate, thereby controlling KM1 to close or open. When the PLC of QX1 is in fault operating state, the monitoring module controls the fault contact relay to operate, thereby controlling KM1 to close. The action contact and fault contact of QX2 are both electrically connected to KM2, and QX2 controls KM2 to close or open.

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