Method and device for detecting contact resistance of voltage criterion type relay protection tripping circuit

Abstract

The application relates to a voltage criterion type relay protection tripping loop contact resistance detection method and device. The voltage criterion type relay protection tripping loop contact resistance detection device comprises a voltage generating circuit and a protection circuit, the protection circuit and the voltage generating circuit are connected in series, and the voltage generating circuit and the protection circuit are connected in parallel with a tripping loop. The voltage generating circuit is used for generating a test signal, the protection circuit is used for balancing the interference of the voltage generating circuit on the tripping loop, a voltage detection point is arranged between the voltage generating circuit and the protection circuit, and the working state of the tripping loop is monitored. The working state of the tripping loop and the abnormal situation of the monitoring circuit can be judged through the voltage data of the voltage detection point by adopting the method, so that whether the tripping loop has the risk of tripping failure can be determined.

Description

Method and device for detecting contact resistance in trip circuits of voltage-criteria relay protection Technical Field

[0001] This application relates to the field of monitoring technology for tripping circuits of smart grid relay protection, and in particular to a method and device for detecting the contact resistance of a voltage criterion-based tripping circuit of relay protection. Background Technology

[0002] In power system relay protection, the trip circuit is an important secondary circuit. Its operation is to open the circuit breaker or disconnect the contactor. The trip command of the protection device is transmitted to the trip coil through the trip circuit to realize the circuit breaker opening, so as to isolate the power grid fault in time and ensure the safe operation of the power grid.

[0003] In the tripping circuit, the current coil of the tripping holding relay passes through the tripping output pressure plate, and then through the switch position auxiliary contact to the tripping coil. The entire circuit, from the protection room to the outdoor switch site, involves a long cable. In the intermediate links, it is difficult to avoid problems such as secondary cable breakage, loose terminal block terminals, poor contact of the pressure plate, or equipment aging, which can lead to increased contact resistance in the tripping circuit. Ultimately, this can cause the tripping circuit to fail, resulting in the switch refusing to operate, and may even trigger a power grid accident and cause significant economic losses. Summary of the Invention

[0004] Therefore, it is necessary to provide a voltage-criteria-based method and device for detecting the contact resistance of a trip circuit in a relay protection system, which can predict the potential risks of the contact resistance in the trip circuit and determine whether the detection device itself has a short circuit or open circuit fault.

[0005] In a first aspect, this application provides a voltage criterion-based relay protection trip circuit contact resistance detection device. The device includes: a monitoring circuit, which comprises a voltage generating circuit and a protection circuit, wherein the protection circuit and the voltage generating circuit are connected in series, and the voltage generating circuit, the protection circuit, and the trip circuit are connected in parallel.

[0006] Voltage generating circuit, used to generate test signals;

[0007] Protection circuits are used to balance the interference of the voltage generation circuit on the tripping circuit;

[0008] A voltage detection point is set between the voltage generating circuit and the protection circuit to monitor the working status of the tripping circuit.

[0009] In one embodiment, the voltage generating circuit includes an AC signal source, a switch, and a first capacitor. One end of the first capacitor is connected to a protection circuit, and the other end of the first capacitor is connected to one end of the switch. The first capacitor, the switch, the AC signal source, and the negative voltage terminal of the trip circuit are connected in series.

[0010] In one embodiment, the protection circuit includes a second capacitor, one end of which is connected to a tripping circuit, and the other end of which is connected to a voltage generating circuit.

[0011] The second capacitor is used to balance the interference of the voltage generating circuit on the trip circuit when the voltage generating circuit is connected to the trip circuit, through the resonance effect of the second capacitor and the components in the trip circuit.

[0012] In one embodiment, the monitoring circuit further includes a control circuit, which is connected to the voltage generating circuit;

[0013] The control circuit is used to acquire the voltage phase and voltage amplitude at the voltage detection point; based on the voltage phase and voltage amplitude, it detects whether any abnormalities have occurred in the monitoring circuit and the tripping circuit.

[0014] In one embodiment, the monitoring circuit further includes a fault alarm circuit, which is connected to the control circuit.

[0015] The fault alarm circuit is used to provide early warning in response to abnormal conditions detected by the control circuit.

[0016] In one embodiment, the control circuit, in performing the function of detecting whether an abnormality has occurred in the monitoring circuit and the trip circuit based on the voltage phase and voltage amplitude, is further configured to:

[0017] If the voltage amplitude is greater than or equal to the preset amplitude threshold and less than the amplitude of the test signal, and the voltage phase is greater than or equal to the preset phase threshold and less than zero degrees, then the contact resistance of the trip circuit is determined to be abnormal.

[0018] In one embodiment, the control circuit, in performing the function of detecting whether an abnormality has occurred in the monitoring circuit and the trip circuit based on the voltage phase and voltage amplitude, is further configured to:

[0019] If the voltage amplitude is greater than zero and less than the preset amplitude threshold, and the voltage phase is less than the preset phase threshold and greater than -90 degrees, then it is determined that no abnormal situation has occurred.

[0020] In one embodiment, the control circuit, in performing the function of detecting whether an abnormality has occurred in the monitoring circuit and the trip circuit based on the voltage phase and voltage amplitude, is further configured to:

[0021] If the voltage amplitude is zero and the voltage phase is zero degrees, then the voltage generating circuit is considered to have an open circuit fault.

[0022] In one embodiment, the control circuit, in performing the function of detecting whether an abnormality has occurred in the monitoring circuit and the trip circuit based on the voltage phase and voltage amplitude, is further configured to:

[0023] If the voltage amplitude is equal to the amplitude of the test signal and the voltage phase is zero degrees, then the voltage generating circuit is determined to have a short circuit fault.

[0024] Secondly, this application also provides a method for detecting the contact resistance of a voltage-criteria-based relay protection trip circuit. This method includes:

[0025] A test signal is generated by a voltage generating circuit;

[0026] The protection circuit balances the interference of the voltage generating circuit on the tripping circuit;

[0027] A voltage detection point is set between the voltage generation circuit and the protection circuit to monitor the operating status of the trip circuit.

[0028] Thirdly, this application also provides an electrical device. This electrical device includes the voltage criterion-based relay protection trip circuit contact resistance detection device described in the first aspect.

[0029] The aforementioned voltage-criteria-based relay protection trip circuit contact resistance detection method and device connects a voltage generating circuit and a protection circuit in parallel to the trip circuit. The voltage generating circuit can generate a test signal, and the protection circuit can balance the interference of the voltage generating circuit on the trip circuit. A voltage detection point is set between the voltage generating circuit and the protection circuit. The operating status of the trip circuit is judged by the voltage data at the voltage detection point, such as the change in contact resistance in the trip circuit, thereby determining whether there is a risk of trip failure in the trip circuit, improving the reliability of the circuit, and increasing the stability of the circuit. Attached Figure Description

[0030] Figure 1 is a schematic diagram of the monitoring circuit provided in one embodiment;

[0031] Figure 2 is a schematic diagram of the monitoring circuit provided in another embodiment;

[0032] Figure 3 is a schematic diagram of the monitoring circuit provided in another embodiment;

[0033] Figure 4 is a schematic diagram of the monitoring circuit provided in another embodiment;

[0034] Figure 5 is a simplified circuit diagram of the monitoring circuit connected to the tripping circuit;

[0035] Figure 6 is a flowchart illustrating a voltage criterion-based relay protection trip circuit contact resistance detection method in one embodiment. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0037] It is understood that the terms “first,” “second,” etc., used in this application may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another.

[0038] It should be understood that the terms “including / comprise” or “have” specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof.

[0039] Relay protection is a crucial link in ensuring the safe and stable operation of power systems. The main control objects of power systems include equipment such as circuit breakers and disconnect switches. Currently, hardware defects in relay protection are one of the main causes of hidden faults. Among them, incorrect protection actions caused by defects in DC operating circuits account for a considerable proportion, such as the DC operating circuit being disconnected due to the burnout of trip circuit components.

[0040] In the intermediate stages of the tripping circuit, issues such as broken secondary cables, loose terminal blocks, poor contact of pressure plates, or aging equipment are unavoidable. These can lead to increased contact resistance in the tripping circuit, causing the circuit breaker or disconnector to fail to operate. Components such as the tripping coil or relay may burn out due to prolonged operating current. Therefore, effective monitoring and early warning of the tripping circuit are crucial for preventing latent faults and minimizing incorrect protection actions. The monitoring circuit provided in this application can be applied to the tripping circuit to promptly determine whether any abnormalities have occurred by monitoring its operating status.

[0041] In one embodiment, as shown in FIG1, a schematic diagram of the monitoring circuit in a voltage criterion type relay protection trip circuit contact resistance detection device is provided. The monitoring circuit is associated with the trip circuit 102. The monitoring circuit in this embodiment may include a voltage generating circuit 104 and a protection circuit 106, wherein the voltage generating circuit 104 and the protection circuit 106 are connected in series, and the voltage generating circuit 104 and the protection circuit 106 are connected in parallel to the trip circuit 102.

[0042] In one possible implementation, one end of the protection circuit 106 is connected to the trip circuit 102, and the other end of the protection circuit 106 is connected to one end of the voltage generating circuit 104. The other end of the voltage generating circuit 104 is connected to the negative terminal of the voltage source of the trip circuit 102.

[0043] The voltage generating circuit 104 in this embodiment is used to generate a test signal. Exemplarily, the voltage generating circuit 104 in this embodiment may include an AC signal generator, particularly a high-frequency AC signal generator, and may also include a main control chip and an opto-relay. The test signal may be an AC signal, particularly a high-frequency AC signal. When the voltage generating circuit 104 includes a main control chip and an opto-relay, the main control chip can control the opto-relay to generate a high-frequency AC signal.

[0044] The protection circuit 106 in this embodiment is used to balance the interference of the voltage generating circuit 104 on the trip circuit 102. Exemplarily, the protection circuit 106 can resonate with some components in the trip circuit 102, thereby balancing the interference of the voltage generating circuit 104 on the trip circuit 102.

[0045] In this embodiment, a voltage detection point 108 is provided between the voltage generating circuit 104 and the protection circuit 106 to monitor the operating status of the trip circuit 102. The operating status of the trip circuit 102 includes a normal state and an abnormal state. An abnormal state of the trip circuit 102 includes an increase in the contact resistance R3. By monitoring the change in contact resistance in the trip circuit 102 through the voltage detection point 108, it is possible to determine whether there is a risk of tripping failure in the trip circuit 102.

[0046] In one possible implementation, the voltage detection point 108 can also be used to monitor the monitoring circuit body provided in the embodiments of this application. For example, the voltage detection point 108 can be used to monitor whether the voltage generating circuit 104 has a short circuit or open circuit or other faults.

[0047] In another possible implementation, the monitoring circuit provided in this application embodiment further includes a voltage detection circuit. The voltage detection circuit is connected to the connection node between the voltage generating circuit 104 and the protection circuit 106, and is used to detect the voltage data at the voltage detection point 108. The voltage detection circuit can be, but is not limited to, a resistor divider circuit.

[0048] In the aforementioned voltage-criteria-type relay protection trip circuit contact resistance detection device, a monitoring circuit is set up in which a voltage generating circuit 104 and a protection circuit 106 are connected in parallel to the trip circuit 102. The voltage generating circuit 104 can generate a test signal, and the protection circuit 106 can balance the interference of the voltage generating circuit 104 on the trip circuit 102. A voltage detection point 108 is set between the voltage generating circuit 104 and the protection circuit 106. The operating status of the trip circuit 102 is determined by the voltage data of the voltage detection point 108, such as the change in the contact resistance R3 in the trip circuit 102, thereby determining whether there is a risk of tripping failure in the trip circuit 102 and improving the reliability of the circuit.

[0049] In one embodiment, Figure 2 shows a schematic diagram of a monitoring circuit provided in another embodiment. Based on the above embodiments, this application describes the relevant content of the voltage generating circuit 104. As shown in Figure 2, the voltage generating circuit 104 in this application embodiment may include: an AC signal source S, a switch K, and a first capacitor C1. One end of the first capacitor C1 is connected to the protection circuit 106, and the other end of the first capacitor C1 is connected to one end of the switch K. The other end of the switch K is connected to the AC signal generator S. That is, the first capacitor C1, the switch K, the AC signal source S, and the negative terminal of the voltage source of the trip circuit 102 are connected in series.

[0050] In one possible implementation, the first capacitor C1 can be used to AC couple the AC signal generated by the AC signal source S. Its capacitive reactance can be used to divide the voltage between the capacitor and the contact resistance R3 of the trip circuit 102, which is more conducive to monitoring the change in the resistance value of the contact resistance R3 of the trip circuit based on the voltage data of the voltage detection point.

[0051] In one possible implementation, when switch K is in the open state, the first capacitor C1 and protection circuit 106 are not connected to the trip circuit 102. At this time, initialization detection can be performed by using the voltage data of the voltage detection point to determine whether each device is normal.

[0052] For example, the AC signal source S generates a high-frequency AC test signal, and the switch K is in the open state. Under normal circumstances, the AC voltage data at the voltage detection point, including the voltage amplitude and voltage phase, are both zero. Under abnormal circumstances, such as a short circuit fault in the protection circuit 106, the voltage amplitude or voltage phase at the voltage detection point is not zero.

[0053] In one possible implementation, when switch K is in the closed state, the first capacitor C1 and the protection circuit 106 are connected to the trip circuit 102, and the working status of the trip circuit or the abnormal condition of the monitoring circuit is monitored by the voltage data of the voltage detection point.

[0054] In this embodiment, the voltage generating circuit 104 includes an AC signal source S, a switch K, and a first capacitor C1. The AC signal source generates an AC test signal. The open state of the switch K initializes the monitoring circuit to determine whether the components of the monitoring circuit are normal. The closed state of the switch K connects the first capacitor C1 and the protection circuit 106 to the trip circuit 102. The first capacitor C1 is used to AC couple the AC signal generated by the AC signal source S. The capacitive reactance of the first capacitor C1 is used to divide the voltage with the contact resistance R3 of the trip circuit 102 so as to monitor the working status of the trip circuit or the abnormal condition of the monitoring circuit through the voltage data of the voltage detection point.

[0055] In one embodiment, Figure 3 shows a schematic diagram of a monitoring circuit provided in another embodiment. This application describes the relevant content of the protection circuit 106. As shown in Figure 3, the protection circuit 106 in this application embodiment may include: a second capacitor C2, one end of the second capacitor C2 is connected to the trip circuit 102, and the other end of the second capacitor C2 is connected to the voltage generating circuit 104.

[0056] The second capacitor C2 is used to balance the interference of the voltage generating circuit 104 on the trip circuit 102 when the voltage generating circuit 104 is connected to the trip circuit. This is achieved through the resonance between the second capacitor C2 and the components within the trip circuit 102. For example, the second capacitor C2 can resonate with the trip coil L1 and the trip holding relay coil TBJI in the trip circuit 102 to balance the relay inductive reactance. Through resonance (zero phase), the interference of the monitoring circuit on the trip circuit 102 is reduced.

[0057] In one possible implementation, the second capacitor C2 can also protect the components in the voltage generating circuit 104 from damage by the DC high-voltage signal of the trip circuit 102 when a short-circuit fault occurs in the voltage generating circuit 104. For example, the voltage generating circuit 104 may include an AC signal source S and a first capacitor C1. When the first capacitor C1 is short-circuited, the second capacitor C2 in the protection circuit 106 can protect the AC signal source S, preventing it from being damaged by the DC high-voltage signal of the trip circuit 102.

[0058] In this embodiment, a second capacitor C2 is provided in the protection circuit 106 to balance the interference of the monitoring circuit on the trip circuit 102 through resonance.

[0059] In one embodiment, the monitoring circuit of the voltage criterion-type relay protection trip circuit contact resistance detection device provided in this application further includes a control circuit, which is connected to the voltage generation circuit 104. The control circuit is used to acquire the voltage phase and voltage amplitude at the voltage detection point, and based on the voltage phase and voltage amplitude, detect whether any abnormalities have occurred in the monitoring circuit and the trip circuit 102.

[0060] In one possible implementation, the voltage generating circuit 104 includes a switch K, and the control circuit can also control the switch K in the voltage generating circuit 104 to be in an open or closed state.

[0061] For example, the voltage generating circuit 104 includes a switch K and an AC signal source S, which generates a high-frequency AC test signal. In this embodiment, the control circuit controls the switch K to be in the open state, acquires the voltage phase and voltage amplitude at the voltage detection point, and determines whether each device is normal based on the voltage phase and voltage amplitude at the voltage detection point. If the voltage amplitude or voltage phase at the voltage detection point is not zero, the protection circuit 106 may have a short circuit fault.

[0062] For example, in the embodiment of this application, when the control circuit controls the switch K to be in the closed state, the voltage generating circuit 104 and the protection circuit 106 are connected to the trip circuit 102. The working status of the trip circuit or the abnormal condition of the monitoring circuit is monitored by the voltage data of the voltage detection point.

[0063] In one possible implementation, the monitoring circuit provided in this application embodiment includes a voltage detection circuit connected to the connection node of the voltage generating circuit 104 and the protection circuit 106, for detecting voltage data at voltage detection point 108. The control circuit in this application embodiment can be connected to the voltage detection circuit to obtain the voltage phase and voltage amplitude of the voltage detection point from the voltage detection circuit.

[0064] In this embodiment, the voltage phase and voltage amplitude of the voltage detection point are obtained through the control circuit, and the monitoring circuit and trip circuit 102 are judged to be abnormal based on the voltage phase and voltage amplitude.

[0065] In one embodiment, the monitoring circuit provided in this application further includes a fault alarm circuit, which is connected to the control circuit described above and is used to issue an early warning in response to an abnormal situation detected by the control circuit.

[0066] In this embodiment of the application, a fault alarm circuit issues a timely warning to avoid significant economic losses caused by the failure of the circuit breaker or disconnector to operate when a line fault occurs.

[0067] In one embodiment, the control circuit provided in this application is further configured to detect whether an abnormality has occurred in the monitoring circuit and the trip circuit 102 based on the voltage phase and voltage amplitude, and to determine that the contact resistance of the trip circuit is abnormal if the voltage amplitude is greater than or equal to a preset amplitude threshold and less than the amplitude of the test signal, and the voltage phase is greater than or equal to a preset phase threshold and less than zero degrees.

[0068] For example, the control circuit can control the voltage generating circuit 104 and the protection circuit 106 to connect to the trip circuit 102, measure and record the voltage amplitude and voltage phase at the voltage detection point. If the voltage amplitude is greater than or equal to the amplitude preset threshold and less than the amplitude of the test signal, and the voltage phase is greater than or equal to the phase preset threshold and less than zero degrees, then it is determined that the contact resistance of the trip circuit 102 is too large, that is, the trip circuit is detected to be in an abnormal state. The control circuit can control the fault alarm circuit to issue a warning.

[0069] This embodiment of the application compares the voltage amplitude at the voltage detection point with the magnitude of the preset amplitude threshold, and also compares the voltage phase at the voltage detection point with the magnitude of the preset phase threshold, thereby determining the change in contact resistance of the trip circuit 102.

[0070] In one embodiment, the control circuit provided in this application is further configured to detect whether an abnormal situation has occurred in the monitoring circuit and the trip circuit 102 based on the voltage phase and voltage amplitude. If the voltage amplitude is greater than zero and less than the amplitude preset threshold, and the voltage phase is less than the phase preset threshold and greater than -90 degrees, then it is determined that no abnormal situation has occurred.

[0071] For example, the control circuit can control the voltage generating circuit 104 and the protection circuit 106 to connect to the trip circuit 102, measure and record the voltage amplitude and voltage phase at the voltage detection point. If the voltage amplitude is greater than zero and less than the amplitude preset threshold, and the voltage phase is less than the phase preset threshold and greater than -90 degrees, then the contact resistance of the trip circuit 102 is determined to be normal, that is, the trip circuit is detected to be in normal working condition.

[0072] This embodiment of the application compares the voltage amplitude of the voltage detection point with the magnitude of the amplitude preset threshold, and also compares the voltage phase of the voltage detection point with the magnitude of the phase preset threshold, thereby determining whether the contact resistance of the trip circuit 102 is under normal conditions.

[0073] In one embodiment, the control circuit provided in this application is further configured to detect whether an abnormality has occurred in the monitoring circuit and the trip circuit 102 based on the voltage phase and voltage amplitude, and to determine that the voltage generating circuit 104 has an open circuit fault if the voltage amplitude is equal to zero and the voltage phase is equal to zero degrees.

[0074] For example, the control circuit can control the voltage generating circuit 104 and the protection circuit 106 to connect to the trip circuit 102, measure and record the voltage amplitude and voltage phase at the voltage detection point. If the voltage amplitude is equal to zero and the voltage phase is equal to zero degrees, it is determined that the voltage generating circuit 104 has an open circuit fault, that is, the monitoring circuit is abnormal.

[0075] This application embodiment compares the voltage amplitude at the voltage detection point with a preset amplitude threshold, and also compares the voltage phase at the voltage detection point with a preset phase threshold, thereby determining whether the monitoring circuit is malfunctioning.

[0076] In one embodiment, the control circuit provided in this application is further configured to detect whether an abnormality has occurred in the monitoring circuit and the trip circuit 102 based on the voltage phase and voltage amplitude. If the voltage amplitude is equal to the amplitude of the test signal and the voltage phase is equal to zero degrees, then it is determined that a short circuit fault has occurred in the voltage generating circuit 104, i.e., the monitoring circuit is abnormal.

[0077] For example, the control circuit can control the voltage generating circuit 104 and the protection circuit 106 to connect to the trip circuit 102, measure and record the voltage amplitude and voltage phase at the voltage detection point. If the voltage amplitude is equal to the amplitude of the test signal and the voltage phase is equal to zero degrees, it is determined that the voltage generating circuit 104 has a short circuit fault, that is, the monitoring circuit is abnormal.

[0078] This application embodiment compares the voltage amplitude at the voltage detection point with a preset amplitude threshold, and also compares the voltage phase at the voltage detection point with a preset phase threshold, thereby determining whether the monitoring circuit is malfunctioning.

[0079] In one embodiment, Figure 4 is a schematic diagram of the monitoring circuit provided in another embodiment. Based on the above embodiments, this application describes the relevant content of the monitoring circuit.

[0080] As shown in Figure 4, a traditional tripping circuit 102 typically includes a switch position relay R1, a trip holding relay TBJ, a protection trip contact BT, a trip output pressure plate XB, a contact resistor R3, a trip holding relay coil TBJI, a circuit breaker position contact DL, and a trip coil L1. The positive terminal of the voltage source, the protection trip contact BT, the trip output pressure plate XB, the contact resistor R3, the trip holding relay coil TBJI, the circuit breaker position contact DL, the trip coil L1, and the negative terminal of the voltage source are connected in series. The trip holding relay TBJ is connected in parallel with the protection trip contact BT, the trip output pressure plate XB, and the contact resistor R3. The switch position relay R1 is connected in parallel with the trip holding relay coil TBJI.

[0081] The monitoring circuit in this embodiment includes a voltage generating circuit 104 and a protection circuit 106. The voltage generating circuit 104 includes an AC signal source S, a switch K, and a first capacitor C1. The protection circuit 106 includes a second capacitor C2. The AC signal source S, switch K, first capacitor C1, and second capacitor C2 are connected in series. One end of the second capacitor C2 is connected to the first capacitor C1, and the other end of the second capacitor C2 is connected to the contact of the protection trip contact BT and the trip output pressure plate XB. A voltage detection point 108 is provided between the first capacitor C1 and the second capacitor C2.

[0082] In this embodiment, the AC signal source S is used to generate a high-frequency AC test signal, the amplitude of which is set to Us and the phase φ is zero degrees.

[0083] The monitoring circuit in this embodiment further includes a voltage detection circuit, which is connected to the voltage detection point 108 and is used to detect the voltage amplitude and voltage phase of the voltage detection point 108.

[0084] The monitoring circuit in this embodiment further includes a control circuit and a fault alarm circuit. The control circuit is connected to the voltage generating circuit 104, the fault alarm circuit, and the voltage detection circuit, respectively. The control circuit is used for:

[0085] When the control switch K is open, during initialization, the system checks whether each component of the monitoring circuit is functioning properly. It obtains the voltage amplitude and voltage phase of the voltage detection point 108 from the voltage detection circuit. If the voltage amplitude or voltage phase of the voltage detection point is not zero, the second capacitor C2 may have a short circuit fault. If the voltage amplitude or voltage phase of the voltage detection point is zero, then each component is in normal condition.

[0086] When control switch K is closed, the voltage generating circuit 104 and protection circuit 106 are connected to the trip circuit 102. The voltage amplitude U0 and voltage phase φ0 at voltage detection point 108 are obtained from the voltage detection circuit. The voltage amplitude at the voltage detection point is compared with a preset amplitude threshold, and the voltage phase at the voltage detection point is also compared with a preset phase threshold. Let the voltage amplitude be U0, the voltage phase be φ0, and the preset amplitude threshold be U... ref The preset phase threshold is φ ref ,but:

[0087] If U ref ≤U0<U S , and φ ref If ≤φ0<0°, it indicates that the contact resistance is too high, indicating that the contact resistance of the trip circuit is abnormal, and the control fault alarm circuit issues a warning.

[0088] If 0 < U, 0 < U ref And -90° < φ0 < φref When the value is low, it indicates that the contact resistance is small, and the contact resistance of the trip circuit is normal.

[0089] If U0 = 0 and φ0 = 0, it indicates that the first capacitor C1 has an open circuit fault, and the control fault alarm circuit will issue a warning.

[0090] If U0 = Us and φ0 = 0, it indicates that the first capacitor C1 has a short circuit fault, and the control fault alarm circuit issues a warning.

[0091] To further illustrate the embodiments of this application, the following will describe the amplitude preset threshold as U. ref The preset phase threshold is φ ref The setup process.

[0092] Referring to Figure 4, the DC voltage U between the positive and negative terminals of the trip circuit 102 dc The equivalent resistance R1 of the switch position relay, the equivalent inductance L of the trip holding relay coil TBJI, the first capacitor C1 and the second capacitor C2 when the switch K is closed, and the high-frequency AC test signal from the AC signal source S are all known parameters. The value of the contact resistance R3 is unknown. The equivalent inductance L1 of the trip coil L1 needs to be verified through multiple tests when not tripping to obtain its value. When the circuit breaker is in the closed position preparing to trip, the circuit breaker position contact DL is closed, and its resistance can be ignored. The trip holding relay TBJ and the protection trip contact BT are open.

[0093] Figure 5 shows a simplified circuit diagram of the monitoring circuit connected to the trip circuit. The high-frequency AC test signal is assumed to be an AC (Alternating Current) signal with a frequency of f and an amplitude of Us.

[0094] When selecting the capacitance value of the second capacitor C2, the concept of resonance (zero phase) is used. The second capacitor C2, the trip coil L1, and the trip holding relay coil TBJI resonate to balance the interference from the monitoring circuit on the trip circuit. The equivalent inductance of the trip coil L1 and the trip holding relay coil TBJI varies depending on the scenario. The equivalent inductance of the trip coil L1 needs to be verified through multiple tests under non-trip conditions. The equivalent inductance of the trip holding relay coil TBJI can be obtained from the TBJI relay manual.

[0095] According to the resonance calculation formula: Conclusion:

[0096] Where ω=2πf, f is the frequency of the high-frequency AC test signal, C2 is the capacitance of the second capacitor C2, L1 is the equivalent inductance of the trip coil L1, and L is the equivalent inductance of the trip holding relay coil TBJI.

[0097] By balancing the trip coil L1 and the trip holding relay coil TBJI through the second capacitor C2, the circuit in Figure 5 can be simplified to an AC signal source, the first capacitor C1, and the contact resistor R3 connected in series, with the voltage amplitude at the voltage detection point being [value missing]. The voltage phase at the voltage detection point is The range of values ​​for U0 is 0 < U0 < U S The value range of φ0 is -90° < φ0 < 0°.

[0098] Based on the value ranges of U0 and φ0 mentioned above, the threshold U can be... ref and threshold φ ref The threshold value is set to half of the range, thereby reducing the decrease in sensitivity and accuracy in determining contact resistance caused by uneven range size. Therefore, this embodiment of the application can set a preset threshold value U. ref =1 / 2Us, phase preset threshold φ ref = -45°.

[0099] For example, suppose the high-frequency AC test signal has a ground frequency of 10kHz, an effective amplitude of 10V, a positive waveform, a contact resistor R3 with a resistance of 100Ω, a first capacitor C1 with a value of 160nF, and a preset phase threshold φ. ref -45°, amplitude preset threshold U ref It is 5V.

[0100] When 5V≤U0<10V and -45°≤φ0<0°, it indicates that the contact resistance is greater than 100Ω, the contact resistance is too high, the trip circuit is abnormal, and the control circuit will control the fault alarm circuit to issue a warning. When 0<U0<5V and -90°<φ0<-45°, it indicates that the contact resistance is less than 100Ω, the contact resistance is small, and the contact resistance of the relay protection trip circuit is normal. When U0=0 and φ0=0, it indicates that the first capacitor C1 has an open circuit fault, the monitoring circuit is abnormal, and the control circuit will control the fault alarm circuit to issue a warning. When U0=Us and φ0=0, it indicates that the first capacitor C1 has a short circuit fault, the monitoring circuit is abnormal, and the control circuit will control the fault alarm circuit to issue a warning.

[0101] The voltage-criteria-based relay protection trip circuit contact resistance detection device proposed in this application uses an AC-coupled voltage detection method. It includes a high-frequency AC test signal source, a switch, a first capacitor, and a second capacitor. The first capacitor, the second capacitor, and the switch are connected in parallel between the high-frequency AC test signal source and the positive terminal of the trip output pressure plate. A voltage detection point is added between the first and second capacitors. By comparing the voltage phase and amplitude at the detection point with preset phase and amplitude thresholds, it determines whether the contact resistance of the relay protection trip circuit has increased or decreased. Simultaneously, it can also determine abnormal conditions in the monitoring circuit based on the voltage phase and amplitude at the detection point, possessing a self-testing function. Compared to current DC-coupled current detection methods, which suffer from issues such as lack of DC bias isolation in the monitoring circuit and contact resistance failure, this application embodiment can accurately and quickly determine whether a switch tripping failure is likely. This facilitates real-time detection of defects such as increased contact resistance in the trip circuit, preventing safety accidents and significant economic losses caused by switch failure.

[0102] Based on the same inventive concept, this application also provides a method for detecting the contact resistance of a voltage-criteria-based relay protection trip circuit. Figure 6 shows a flowchart of one embodiment of the method for detecting the contact resistance of a voltage-criteria-based relay protection trip circuit. The method for detecting the contact resistance of a voltage-criteria-based relay protection trip circuit in this application can be applied to the voltage-criteria-based relay protection trip circuit contact resistance detection device provided in the above embodiments of this application. As shown in Figure 6, the method of this application embodiment may include the following steps:

[0103] Step 602: Generate a test signal through a voltage generating circuit.

[0104] Step 604: Balance the interference of the voltage generating circuit on the trip circuit through the protection circuit.

[0105] Step 606: Set up a voltage detection point between the voltage generation circuit and the protection circuit to monitor the working status of the trip circuit.

[0106] Among them, the voltage data of the voltage detection point can be collected by software timed self-collection, by operation panel of the operation box, or by remote command collection.

[0107] The voltage criterion-based relay protection trip circuit contact resistance detection method provided in this application embodiment can be applied to the voltage criterion-based relay protection trip circuit contact resistance detection device provided in the above embodiment of this application. Its implementation principle and technical effect are similar, and will not be repeated here.

[0108] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages in other steps.

[0109] In one embodiment, a power device is provided, including the voltage criterion type relay protection trip circuit contact resistance detection device provided in the above embodiments of this application. Its implementation principle and technical effect are similar, and will not be described again here.

[0110] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0111] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A voltage-criteria type relay protection trip circuit contact resistance detection device, characterized in that, The system includes a monitoring circuit, which comprises a voltage generating circuit and a protection circuit. The protection circuit and the voltage generating circuit are connected in series, and the voltage generating circuit, the protection circuit, and the tripping circuit are connected in parallel. The voltage generating circuit generates an AC test signal. One end of the protection circuit is connected to the tripping circuit, and the other end is connected to the voltage generating circuit. The other end of the voltage generating circuit is connected to the negative terminal of the voltage source of the tripping circuit. The protection circuit resonates with the devices in the tripping circuit when the voltage generating circuit is connected to the tripping circuit to balance the interference of the voltage generating circuit on the tripping circuit. A voltage detection point is provided between the voltage generating circuit and the protection circuit to monitor the operating status of the tripping circuit. The monitoring circuit also includes a control circuit connected to the voltage generating circuit. The control circuit acquires the voltage phase and voltage amplitude of the voltage detection point and detects whether any abnormalities have occurred in the monitoring circuit and the tripping circuit based on the voltage phase and voltage amplitude. When the control circuit performs the step of detecting whether the monitoring circuit and the trip circuit have an abnormality based on the voltage phase and the voltage amplitude, it is configured to: if the voltage amplitude is greater than or equal to a preset amplitude threshold and less than the amplitude of the test signal, and the voltage phase is greater than or equal to a preset phase threshold and less than zero degrees, then the contact resistance of the trip circuit is determined to be abnormal.

2. The apparatus according to claim 1, characterized in that, The voltage generating circuit includes an AC signal source, a switch, and a first capacitor. One end of the first capacitor is connected to the protection circuit, and the other end of the first capacitor is connected to one end of the switch. The other end of the switch is connected to one end of the AC signal source, and the other end of the AC signal source is connected to the negative terminal of the voltage source of the trip circuit.

3. The apparatus according to claim 1, characterized in that, The protection circuit includes a second capacitor, one end of which is connected to the trip circuit, and the other end of which is connected to the voltage generating circuit. The second capacitor is used to balance the interference of the voltage generating circuit to the trip circuit through the resonance effect of the second capacitor and the devices in the trip circuit when the voltage generating circuit is connected to the trip circuit.

4. The apparatus according to claim 1, characterized in that, The monitoring circuit also includes a fault alarm circuit, which is connected to the control circuit; the fault alarm circuit is used to issue an early warning in response to abnormal conditions detected by the control circuit.

5. The apparatus according to claim 1, characterized in that, The control circuit, when performing the step of detecting whether an abnormal situation has occurred in the monitoring circuit and the tripping circuit based on the voltage phase and the voltage amplitude, is further configured to: if the voltage amplitude is greater than zero and less than a preset amplitude threshold, and the voltage phase is less than a preset phase threshold and greater than -90 degrees, then it is determined that no abnormal situation has occurred.

6. The apparatus according to claim 1, characterized in that, The control circuit, in performing the step of detecting whether the monitoring circuit and the trip circuit have abnormal conditions based on the voltage phase and the voltage amplitude, is further configured to: if the voltage amplitude is equal to zero and the voltage phase is equal to zero degrees, then determine that the voltage generating circuit has an open circuit fault.

7. The apparatus according to claim 1, characterized in that, The control circuit, in performing the step of detecting whether the monitoring circuit and the trip circuit have abnormal conditions based on the voltage phase and the voltage amplitude, is further configured to: if the voltage amplitude is equal to the amplitude of the test signal and the voltage phase is equal to zero degrees, then determine that the voltage generating circuit has a short circuit fault.

8. A method for detecting the contact resistance of a voltage-criteria type relay protection trip circuit, applied to the device described in any one of claims 1 to 7, characterized in that, include: A test signal is generated by a voltage generating circuit; when the voltage generating circuit is connected to the trip circuit, the protection circuit resonates with the devices in the trip circuit to balance the interference of the voltage generating circuit to the trip circuit; a voltage detection point is set between the voltage generating circuit and the protection circuit to monitor the working status of the trip circuit.

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