On-load tap changer switching circuits, systems, equipment and fault diagnosis methods

Abstract

This invention provides an on-load tap changer switching circuit, system, device, and fault diagnosis method, relating to the field of transformer technology. A power supply module controls the opening and closing of the on-load tap changer switching circuit; a transformer module regulates the voltage of the power supply module; a switching core module adjusts the voltage ratio of the transformer module or switches the circuit; an LC resonant module generates power frequency current in the switching circuit while preventing the impact of sudden current changes in the switching core module on the transformer module during switching; and a current-limiting resistor module limits the unstable current generated by the LC resonant module. This invention compares the electrical waveforms obtained from simulated switching with abnormal electrical waveforms in actual switching tests to analyze and locate faults related to abnormal electrical waveforms. Furthermore, the simulation model built by this invention supports monitoring the voltage and current data of any switch in the on-load tap changer switching core during simulated switching.

Description

Technical Field

[0001] This invention relates to the field of transformer technology, specifically to on-load tap changer switching circuits, systems, equipment, and fault diagnosis methods. Background Technology

[0002] With the development of the times, users have put forward higher requirements for power quality. Voltage stability is one of the main technical indicators for measuring power quality. However, power generation and consumption cannot be kept in balance, and voltage fluctuations are inevitable. This necessitates on-load tap changers for voltage regulation. An on-load tap changer is a switching device that can provide a constant voltage to the transformer even when the load changes. It can regulate reactive power, compensate for voltage fluctuations, and adjust the converter firing angle. Currently, more than 90% of converter transformers in China, ranging from 10 to 500kV, are equipped with on-load tap changers. The on-load tap changer is the core component for transformers to achieve on-load voltage regulation.

[0003] Early on-load tap changers relied on copper-tungsten contacts for load switching, but this resulted in significant contact burn-out, oil carbonization, and contamination, increasing daily maintenance workload for users. In the 21st century, the trend towards oil-free power equipment provided unprecedented development opportunities for vacuum tap changers, leading to their widespread application. Vacuum on-load tap changers eliminate oil carbonization and contamination, require no contact replacement, and can withstand over 300,000 maintenance-free operations, essentially achieving maintenance-free operation within their service life. However, due to their complex structure and frequent operation, the rate of operational errors and failures increases with the number of voltage regulation cycles, making them prone to mechanical failures or electrical accidents, often resulting in substantial economic losses and serious social impacts.

[0004] Currently, the switching core of a vacuum on-load tap changer is immersed in insulating oil, and the switches within the core are arranged closely together. This makes it impossible to monitor the voltage and current of each switch individually during actual switching. Only the voltage and current on the odd-numbered side (also known as the N-side) and even-numbered side (also known as the N+1 side) of the on-load tap changer can be measured. Therefore, when abnormal electrical waveforms are obtained during on-load tap changer switching, it is impossible to identify the faulty switch within the core and the type of fault. This poses a significant challenge to the analysis of faults in vacuum on-load tap changers. Vacuum on-load tap changers still face considerable challenges in fault diagnosis, lifespan improvement, and achieving maintenance-free operation. Summary of the Invention

[0005] This invention provides an on-load tap changer switching circuit, system, device, and fault diagnosis method to solve the problem that when an on-load tap changer fails, it is impossible to identify the faulty switch and the type of fault.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] An on-load tap changer switching circuit includes: a power supply module, a transformer module, a switching core module, an LC resonant module, and a current-limiting resistor module. The power supply module is connected to the transformer module and is used to control the opening and closing of the on-load tap changer switching circuit. The transformer module is connected to the switching core module and the current-limiting resistor module and is used to regulate the voltage of the power supply module. The switching core module is connected to the LC resonant module and is used to adjust the voltage ratio of the transformer module or to switch the on-load tap changer switching circuit. The LC resonant module is connected to the current-limiting resistor module and is used to generate power frequency current in the on-load tap changer switching circuit, while avoiding the impact of sudden current changes in the switching core module on the transformer module during switching. The current-limiting resistor module is used to limit the unstable current generated by the LC resonant module. An arc voltage equivalent module is connected to the switching core module and is used to simulate and verify faults in the on-load tap changer switching circuit during switching.

[0008] Furthermore, the power module includes a three-phase power supply component, a three-phase voltage and current measurement component, and a three-phase circuit breaker component. The three-phase power supply component is connected to the three-phase voltage and current measurement component, and the three-phase circuit breaker component is connected to the three-phase power supply component and the transformer module. The transformer module includes a single-phase transformer component.

[0009] Furthermore, the arc voltage equivalent module includes: a DC voltage source component, a circuit breaker component, an ideal switch component b, and an ideal switch component a. The positive terminal of the DC voltage source component is connected to the negative terminal of the circuit breaker component, the negative terminal of the DC voltage source component is connected to the positive terminal of the ideal switch component b, the positive terminal of the ideal switch component a is connected to the positive terminal of the circuit breaker component, and the negative terminal of the ideal switch component a is connected to the negative terminal of the ideal switch component b.

[0010] Furthermore, the switching core module includes: a main test phase switching core circuit and a secondary test phase switching core circuit;

[0011] The main test phase switching core circuit includes: a main test phase switching core, a first changeover switch Z1, a second changeover switch Z2, a main vacuum bulb V1, a first auxiliary vacuum bulb V2, a second auxiliary vacuum bulb V3, a transition resistor R, a first main switch MC1, and a second main switch MC2. The N-side of the main test phase switching core is connected to the positive terminal of the Z11 terminal of the first changeover switch Z1, and the N+1 side of the main test phase switching core is connected to the positive terminal of the Z12 terminal of the first changeover switch Z1. The positive terminal of the Z21 terminal of the second changeover switch Z2 is connected to the negative terminal of the first auxiliary vacuum bulb V2, and the positive terminal of the Z22 terminal of the second changeover switch Z2 is connected to the negative terminal of the second auxiliary vacuum bulb V3. The positive terminal of the main vacuum bulb V1 is connected to the negative terminals of both the Z11 and Z12 terminals, and the negative terminal of the main vacuum bulb V1 is connected to the main test phase switching core. The neutral point of the core; the positive terminal of the first auxiliary vacuum bulb V2 is connected to the N side of the main test phase switching core; the positive terminal of the second auxiliary vacuum bulb V3 is connected to the N+1 side of the main test phase switching core; the positive terminal of the transition resistor R is connected to the negative terminals of Z21 and Z22, and the negative terminal of the transition resistor R is connected to the neutral point of the main test phase switching core; the positive terminal of the first main switch MC1 is connected to the N side of the main test phase switching core, and the negative terminal of the first main switch MC1 is connected to the neutral point of the main test phase switching core; the positive terminal of the second main switch MC2 is connected to the N+1 side of the main test phase switching core, and the negative terminal of the second main switch MC2 is connected to the neutral point of the main test phase switching core; the structure of the auxiliary test phase switching core circuit is the same as that of the main test phase switching core circuit.

[0012] Furthermore, the LC resonant module includes an inductor component and a capacitor component. The positive terminal of the inductor component is connected to the neutral point of the main test phase switching core, the positive terminal of the capacitor component is connected to the neutral point of the auxiliary test phase switching core, and the negative terminal of the inductor component is connected to the negative terminal of the capacitor component.

[0013] Furthermore, the current-limiting resistor module includes: current-limiting resistor R2, current-limiting resistor R3, circuit breaker assembly Z3, and circuit breaker assembly Z4; current-limiting resistor R2 and current-limiting resistor R3 are connected in parallel, current-limiting resistor R2 and circuit breaker assembly Z3 are connected in series, current-limiting resistor R3 and circuit breaker assembly Z4 are connected in series, and the resistance value of current-limiting resistor R2 is greater than the resistance value of current-limiting resistor R3.

[0014] A fault diagnosis method for an on-load tap changer circuit, based on the on-load tap changer circuit, includes the following steps:

[0015] Obtain abnormal electrical waveforms from the actual test of the on-load tap changer switching circuit; start the power supply module to begin simulation and obtain the simulated electrical waveforms of the N-side and N+1-side of the main test phase switching core circuit;

[0016] The abnormal electrical waveform and the simulated electrical waveform are compared, and the switching action times of the first main switch MC1 and the second main switch MC2 are modified. The action times of all other switching components in the switching core module are synchronously adjusted according to the start action times of the first main switch MC1 and the second main switch MC2 to obtain a simulated electrical waveform with the same phase as the abnormal electrical waveform.

[0017] By comparing the abnormal electrical waveform with the simulated electrical waveform that has the same phase, the fault reflected by the abnormal electrical waveform can be preliminarily located and analyzed.

[0018] The arc voltage equivalent module is connected in series to the main test phase switching core circuit and the auxiliary test phase switching core circuit respectively to simulate the fault reflected by the abnormal electrical waveform and obtain a simulated electrical waveform that takes into account the fault reflected by the abnormal electrical waveform.

[0019] By comparing the simulated electrical waveform reflecting the fault with the abnormal electrical waveform, if the two waveforms are similar and their waveform characteristics match, the verification of the fault reflected by the abnormal electrical waveform is completed.

[0020] A system for fault diagnosis of on-load tap changer circuits, based on the aforementioned fault diagnosis method, includes:

[0021] The waveform acquisition module is used to acquire abnormal electrical waveforms in the actual test of the on-load tap changer switching circuit; it starts the power supply module to begin simulation and obtains the simulated electrical waveforms of the N-side and N+1-side of the main test phase switching core circuit; the simulation timing modification module is used to compare the abnormal electrical waveforms with the simulated electrical waveforms, modify the switching action times of the first main switch MC1 and the second main switch MC2, and synchronously adjust the action times of all other switching components in the switching core module according to the start action times of the first main switch MC1 and the second main switch MC2 to obtain simulated electrical waveforms with the same phase as the abnormal electrical waveforms; the preliminary fault location analysis module... The system uses a fault simulation module to compare abnormal electrical waveforms with simulated electrical waveforms that have the same phase characteristics as the abnormal electrical waveforms, and to preliminarily locate and analyze the faults reflected by the abnormal electrical waveforms. The fault simulation module connects the arc voltage equivalent module in series with the main test phase switching core circuit and the auxiliary test phase switching core circuit, respectively, to simulate the faults reflected by the abnormal electrical waveforms, obtaining simulated electrical waveforms that consider the faults reflected by the abnormal electrical waveforms. The fault verification module compares the simulated electrical waveforms that consider the faults reflected by the abnormal electrical waveforms with the abnormal electrical waveforms. If the two waveforms are similar and their waveform characteristics match, the verification of the faults reflected by the abnormal electrical waveforms is completed.

[0022] An electronic device includes a memory, a processor, and a computer program stored in the memory and executable in the processor, wherein the processor executes the computer program to implement the steps of the on-load tap changer circuit fault diagnosis method.

[0023] A computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the on-load tap changer circuit fault diagnosis method.

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

[0025] This invention provides an on-load tap changer switching circuit and establishes a circuit simulation model of the on-load tap changer switching loop. It accurately reproduces the electrical waveforms during the entire switching process of the on-load tap changer. By comparing the electrical waveforms obtained from the simulation with the abnormal electrical waveforms from the actual test, it is possible to locate the faults related to the abnormal electrical waveforms during the on-load tap changer switching process. Furthermore, the model supports monitoring the voltage and current data of any switch in the switching core.

[0026] Furthermore, based on the simulation model of the on-load tap changer switching circuit, this invention provides an arc voltage equivalent module. Since the electrical faults occurring during on-load tap changer switching are mainly related to the arc erosion phenomenon between contacts, the arc voltage equivalent module and the relevant switches where arc erosion occurs between contacts can be connected in series in the simulation model of the on-load tap changer switching circuit. This accurately restores the characteristic electrical waveforms corresponding to the contact erosion situation during actual on-load tap changer switching. It can verify the specific faults corresponding to the abnormal waveforms during on-load tap changer switching, helping to further analyze and understand the details of specific faults, and ultimately providing accurate and powerful theoretical support for improving the lifespan of vacuum on-load tap changers. Attached Figure Description

[0027] Figure 1 A simplified circuit diagram of the actual test of the on-load tap changer switching circuit built for an embodiment of the present invention;

[0028] Figure 2 This is a simplified structural diagram of the on-load tap changer main test phase switching core according to an embodiment of the present invention;

[0029] Figure 3 This is a timing diagram of the operation of each switch of the main test phase switching core when switching from the N side to the N+1 side in an embodiment of the present invention;

[0030] Figure 4 This is a timing diagram of the operation of each switch when the main test phase switching core switches from the N+1 side to the N side in an embodiment of the present invention;

[0031] Figure 5 A simulation model of an on-load tap changer circuit built for an embodiment of the present invention;

[0032] Figure 6 An equivalent module for on-load tap changer arc voltage constructed for an embodiment of the present invention;

[0033] Figure 7 This is an electrical waveform diagram of the on-load tap changer switching from the N side to the N+1 side during an actual test of an embodiment of the present invention;

[0034] Figure 8 This is an electrical waveform diagram of switching from the N-side to the N+1-side in the on-load tap changer simulation switching circuit of this embodiment of the invention;

[0035] Figure 9 This is an electrical waveform diagram of the on-load tap changer switching from the N+1 side to the N side during an actual test according to an embodiment of the present invention;

[0036] Figure 10 This is an electrical waveform diagram of switching from the N+1 side to the N side in the on-load tap changer simulation switching circuit of this embodiment of the invention;

[0037] Figure 11 This is the test abnormal electrical waveform 1 when the on-load tap changer switches from the N+1 side to the N side according to an embodiment of the present invention;

[0038] Figure 12 This is a normal switching simulation electrical waveform in this embodiment of the invention, which has phase conditions similar to the experimental abnormal electrical waveform 1.

[0039] Figure 13 This is the test abnormal electrical waveform 2 when the on-load tap changer switches from the N+1 side to the N side in this embodiment of the invention;

[0040] Figure 14 This is a normal switching simulation electrical waveform in this embodiment of the invention, which has phase conditions similar to the experimental abnormal electrical waveform 2.

[0041] Figure 15 This is a simulation switching circuit for simulating faults related to abnormal electrical waveform 1 in the embodiment of the present invention;

[0042] Figure 16 This is a simulation switching electrical waveform diagram considering the possible fault of the abnormal electrical waveform 1 in the embodiment of the present invention;

[0043] Figure 17 This is a simulation switching circuit for simulating faults related to abnormal electrical waveform 2 in the embodiment of the present invention;

[0044] Figure 18 This is a simulation switching electrical waveform diagram considering the possible faults of the abnormal electrical waveform 2 in the embodiment of the present invention;

[0045] Figure 19 The waveform results are obtained from monitoring the voltage and current data of some major switching components in the main test phase switching core of the on-load tap changer in this embodiment of the invention.

[0046] Figure 20 This is a schematic diagram of the on-load tap changer switching circuit system provided by the present invention;

[0047] Figure 21 A flowchart illustrating the fault diagnosis method for the on-load tap changer switching circuit provided by the present invention.

[0048] Figure 22 This is a schematic diagram of the electronic device structure used in this invention. Detailed Implementation

[0049] The technical solution of the present invention will be described in detail below:

[0050] This invention provides an on-load tap changer switching circuit, system, equipment, and fault diagnosis method, mainly comprising the following three aspects:

[0051] 1. First step: Build a simulation model of the on-load tap changer switching circuit to recreate the various switching processes of the on-load tap changer;

[0052] Simulation model of on-load tap changer circuit as follows Figure 1 As shown, it includes: a power supply module, a transformer module, a switching core module containing a set of identical main test phase switching core circuits and auxiliary test phase switching core circuits, an LC resonant module, and a current limiting resistor module;

[0053] (1) The power supply module adopts a three-phase power supply component. The parameters of the three-phase power supply component are set to 50Hz. Its star neutral point is grounded and the rated voltage is 35000V. The other parameters are all default values. The three-phase power supply component is connected to a three-phase voltage and current measurement component. The three-phase voltage and current measurement component is connected to a three-phase circuit breaker component Z0.

[0054] The initial state parameters of the three-phase circuit breaker assembly Z0 are set to 0, which is the open state. At time 0 when the simulation of the on-load tap changer switching process begins, a step function from "0" to "1" is input to the three-phase circuit breaker assembly Z0 to control the three-phase circuit breaker to close. The three-phase circuit breaker assembly Z0 is connected to a transformer module.

[0055] (2) The transformer module consists of three single-phase transformer components, which respectively regulate the voltage of phases a, b, and c of the three-phase power supply component. These three single-phase transformers are referred to as transformer a, transformer b, and transformer c. The rated capacity parameters of the three single-phase transformers are all set to 6300kVA, the frequency is set to 50Hz, and the primary winding voltage is set to 35kV. In addition, the secondary winding voltage of transformer a is set to 3kV, the secondary winding voltage of transformer b is set to 3315V, and the secondary winding voltage of transformer c is set to 3315V. The other built-in parameters of the three single-phase transformers are the system defaults. The transformer module is connected to the switching core module.

[0056] (3) The switching core module consists of a set of identical main test phase switching cores and auxiliary test phase switching cores. Since the main test phase switching cores and auxiliary test phase switching cores in the switching core module are completely identical and operate synchronously, here we will only introduce the composition of the main test phase switching core and the operating sequence of each switching component.

[0057] The main test phase switching core is divided into an N-side switch and an N+1-side switch. The N-side switch is connected to the positive secondary terminal of transformer b, and the N+1-side switch is connected to the positive secondary terminal of transformer c. During the switching process, the load switches from the N-side switch to the N+1-side switch and then back to the N-side switch, repeating the process. The specific structure of the main test phase switching core is as follows: Figure 2The circuit includes: a first changeover switch Z1, a second changeover switch Z2, a main vacuum bulb V1, a first auxiliary vacuum bulb V2, a second auxiliary vacuum bulb V3, a transition resistor R, a first main switch MC1, and a second main switch MC2. All of these switches are circuit breaker components in Simulink. The positive terminal of the left side (Z11) of the first changeover switch Z1 is connected to the N-side of the main test phase switching core, and the positive terminal of the right side (Z12) of the first changeover switch Z1 is connected to the N+1 side of the main test phase switching core. The positive terminal of the main vacuum bulb V1 is connected to the negative terminals of both Z11 and Z12, and the negative terminal is connected to the neutral point of the main test phase switching core. The positive terminal of the first main switch MC1 is connected to the N-side of the main test phase switching core, and the negative terminal is connected to the neutral point of the main test phase switching core. The positive terminal of the first auxiliary vacuum bulb V2 is connected to the N side of the main test phase switching core; the positive terminal of the second auxiliary vacuum bulb V3 is connected to the N+1 side of the main test phase switching core; the positive terminal of the left side Z21 of the second changeover switch Z2 is connected to the negative terminal of the first auxiliary vacuum bulb V2, and the positive terminal of the right side Z22 of the second changeover switch is connected to the negative terminal of the second auxiliary vacuum bulb V3; the positive terminal of the transition resistor R is connected to both the negative terminals of Z21 and Z22, and the negative terminal is connected to the neutral point of the main test phase switching core; the positive terminal of the second main switch MC2 is connected to the N+1 side of the main test phase switching core, and the negative terminal is connected to the neutral point of the main test phase switching core; all built-in parameters of each circuit breaker component in the switching core module, except for the initial state parameters, are default values;

[0058] When the switching core is in the N-side position, the initial state parameter of the left side Z11 of the first changeover switch Z1 is 1, indicating a closed state; the initial state parameter of the right side Z12 of the first changeover switch Z1 is 0, indicating an open state; the initial state parameter of the main vacuum bulb V1 is 1, indicating a closed state; the initial state parameter of the first main switch MC1 is 1, indicating a closed state; the initial state parameter of the first auxiliary vacuum bulb V2 is 0, indicating an open state; the initial state parameter of the second auxiliary vacuum bulb V3 is 0, indicating an open state; the initial state parameter of the left side Z21 of the second changeover switch Z2 is 1, indicating a closed state; the initial state parameter of the right side Z22 of the second changeover switch Z2 is 0, indicating an open state; the initial state parameter of the second main switch MC2 is 0, indicating an open state.

[0059] When the switching core is in the N+1 side position, the initial state parameter of the left side Z11 of the first changeover switch Z1 is 0, indicating the open state; the initial state parameter of the right side Z12 of the first changeover switch Z1 is 1, indicating the closed state; the initial state parameter of the main vacuum bulb V1 is 1, indicating the closed state; the initial state parameter of the first main switch MC1 is 0, indicating the open state; the initial state parameter of the first auxiliary vacuum bulb V2 is 0, indicating the open state; the initial state parameter of the second auxiliary vacuum bulb V3 is 0, indicating the open state; the initial state parameter of the left side Z21 of the second changeover switch Z2 is 0, indicating the open state; the initial state parameter of the right side Z22 of the second changeover switch Z2 is 1, indicating the open state; and the initial state parameter of the second main switch MC2 is 1, indicating the closed state.

[0060] The on-load tap changer reciprocates between the N side and the N+1 side of the switching core. During the switching process, the timing sequence of the actions of each switch in the switching core is as follows: Figure 3 and Figure 4 The timing sequence of each switch is imported. When the switching core switches from the N side to the N+1 side, the state parameter of the first main switch MC1 changes from 1 to 0, executing the opening action; 20ms later, the state parameters of the first auxiliary vacuum bulb V2 and the second auxiliary vacuum bulb V3 simultaneously change from 0 to 1, executing the closing action; 5ms later, the state parameter of the main vacuum bulb V1 changes from 1 to 0, executing the opening action; 15ms later, the state parameter of the left side Z11 of the first transfer switch Z1 changes from 1 to 0, executing the opening action; 5ms later, the state parameter of the right side Z12 of the first transfer switch Z1 changes from 1 to 0, executing the opening action; The status parameter changes from 0 to 1, triggering a closing action; 15ms later, the status parameter of the main vacuum bulb V1 changes from 0 to 1, triggering a closing action; 5ms later, the status parameters of the first auxiliary vacuum bulb V2 and the second auxiliary vacuum bulb V3 simultaneously change from 1 to 0, triggering a opening action; 15ms later, the status parameter of the left side Z21 of the second transfer switch Z2 changes from 1 to 0, triggering a opening action; 5ms later, the status parameter of the second main switch MC2 changes from 0 to 1, triggering a closing action; 5ms later, the status parameter of the left side Z22 of the second transfer switch Z2 changes from 0 to 1, triggering a closing action.

[0061] When the switching core switches from the N+1 side to the N side, firstly, the state parameter of the first main switch MC2 changes from 1 to 0, executing a tripping action; 20ms later, the state parameters of the first auxiliary vacuum bulb V2 and the second auxiliary vacuum bulb V3 simultaneously change from 0 to 1, executing a closing action; 5ms later, the state parameter of the main vacuum bulb V1 changes from 1 to 0, executing a tripping action; 15ms later, the state parameter of the right side Z12 of the first transfer switch Z1 changes from 1 to 0, executing a tripping action; 5ms later, the state parameter of the left side Z11 of the first transfer switch Z1 changes from 0 to 1. The circuit breaker performs a closing action; 15ms later, the state parameter of the main vacuum bulb V1 changes from 0 to 1, and the circuit breaker performs a closing action; 5ms later, the state parameters of the first auxiliary vacuum bulb V2 and the second auxiliary vacuum bulb V3 simultaneously change from 1 to 0, and the circuit breaker performs a opening action; 15ms later, the state parameter of the right side Z22 of the second transfer switch Z2 changes from 1 to 0, and the circuit breaker performs a opening action; 5ms later, the state parameter of the second main switch MC2 changes from 0 to 1, and the circuit breaker performs a closing action; 5ms later, the state parameter of the right side Z21 of the second transfer switch Z2 changes from 0 to 1, and the circuit breaker performs a closing action.

[0062] The switching core module is connected to the LC resonant module. The LC resonant module can generate power frequency current only in the test circuit, while the current flowing back to the transformer is zero, avoiding the impact of sudden current changes on the transformer during the switching process.

[0063] (4) The LC resonant module includes: an inductor component and a capacitor component, wherein the positive terminal of the inductor component is connected to the neutral point of the main test phase switching core, and the inductance value of the inductor component is determined by the relationship between the capacitance value and the inductance value when resonance occurs. It is confirmed that the positive terminal of the capacitor assembly is connected to the neutral point of the phase switching core under test, and the built-in capacitance value of the capacitor assembly is determined by the capacitance value in the actual test. The negative terminals of the inductor assembly and the capacitor assembly are connected to each other. The current limiting resistor module is connected after the LC resonant module.

[0064] (5) The current limiting resistor module includes two parallel current limiting resistor branches. In the actual test circuit, when the current generated by the LC resonant module is not yet stable, the resistance of the current limiting resistor is 2.64Ω, and after stabilization, the resistance of the current limiting resistor is 0.25Ω.

[0065] The upper current-limiting resistor branch includes: a resistor component R2 with a resistance of 2.64Ω and a control resistor component R2 connected to the circuit breaker component Z3 in the simulation circuit. The positive terminal of resistor component R2 is connected to the negative terminal of circuit breaker component Z3, and the negative terminal of resistor component R2 is connected to the positive terminal of the secondary winding of transformer a. The positive terminal of circuit breaker component Z3 is connected to the common negative terminal of the inductor and capacitor in the LC resonant module. The lower current-limiting resistor branch includes: a resistor component R3 with a resistance of 0.25Ω and a control resistor component R3 connected to the circuit breaker component Z4 in the simulation circuit. The positive terminal of resistor component R3 is connected to the negative terminal of circuit breaker component Z4, and the negative terminal of resistor component R3 is connected to the positive terminal of the secondary winding of transformer a. The positive terminal of circuit breaker component Z4 is connected to the common negative terminal of the inductor and capacitor in the LC resonant module. The common negative terminal of the inductor and capacitor is connected. At the start of the simulation, the LC resonant module is just beginning to discharge, and the generated current and voltage are unstable, requiring a 2.64Ω current-limiting protection resistor. Therefore, the initial state parameter of circuit breaker component Z3 is set to 1, indicating a closed state, so that the 2.64Ω current-limiting resistor R2 is connected to the switching circuit from the beginning of the simulation. The initial state parameter of circuit breaker component Z4 is set to 0, indicating a opened state, so that the 0.25Ω current-limiting resistor R3 is not connected to the switching circuit at the beginning of the simulation. After the current and voltage generated by the LC resonant module stabilize, the state parameter of circuit breaker component Z3 is changed from 1 to 0 to perform the opening action, and at the same time, the state parameter of circuit breaker component Z4 is changed from 0 to 1 to perform the closing action, so that the current-limiting resistor connected to the switching circuit changes from R2 to R3. Thus, the on-load tap changer simulation switching circuit is constructed as follows. Figure 5 As shown, the simulation is then started to obtain the current and voltage of the N-side and N+1-side switches of the main test phase switching core. The electrical waveforms obtained by the simulation are compared with the waveforms under normal switching in the actual test to verify the accuracy of the simulation model.

[0066] 2. Second stage: Using the on-load tap changer simulation switching circuit built in the first stage, the relevant faults of abnormal electrical waveforms that appear in the actual test are located;

[0067] (1) Compare the abnormal electrical waveforms in the actual test with the electrical waveforms obtained by simulation. For the simulated electrical waveforms to be compared, it is necessary to first modify the start time of the first main switch MC1 and the second main switch MC2 in the simulation, and then adjust the start time of all other switches in the switching core according to the start time of the first main switch MC1 and the second main switch MC2, so that the phase of the simulated electrical waveform is consistent with the abnormal electrical waveform in the actual test.

[0068] (2) Compare the abnormal points in the actual experimental abnormal electrical waveforms obtained by comparison with Figure 3 and Figure 4By comparing the switching sequence of the on-load tap changer, the timing range in which the abnormal point occurs during the entire switching process is determined, and the corresponding switches that have performed opening and closing actions within that timing range are identified, thus enabling preliminary location and analysis of the faults related to the abnormal electrical waveforms in the test.

[0069] 3. Third stage: Since most of the abnormal electrical waveforms during the switching process of the on-load tap changer are related to the arcing between the contacts inside the on-load tap changer, an arc voltage equivalent module was built in this stage to simulate the abnormal electrical waveforms that occur during the switching process of the on-load tap changer, so as to further verify the preliminary location and analysis of the faults related to the abnormal electrical waveforms in the second stage.

[0070] (1) The arc voltage equivalent module consists of a DC voltage source component, a circuit breaker component Z5 connected in series with the positive terminal of the DC voltage source, an ideal switch component connected in series with the negative terminal of the DC voltage source (denoted as ideal switch component b), and an ideal switch component connected in parallel with the branch containing the above three components (denoted as ideal switch component a). For the specific simulation model, see Figure 6 The positive terminal of ideal switch component a is connected to the positive terminal of circuit breaker component Z5, forming the positive terminal of the arc voltage equivalent module. The negative terminal of ideal switch component a is connected to the negative terminal of ideal switch component b, forming the negative terminal of the arc voltage equivalent module. The negative terminal of circuit breaker component Z5 is connected to the positive terminal of the DC voltage source, and the negative terminal of the DC voltage source is connected to the positive terminal of ideal switch component b. Ideal switch component a controls the time when the entire arc voltage equivalent module is connected to the switching simulation circuit. During normal switching, the arc voltage equivalent module does not need to be connected to the switching simulation circuit, so the initial state parameter of ideal switch component a is set to 1, which is the closed state, causing the DC voltage source to be short-circuited. All other built-in parameters are set to default values. Circuit breaker component Z5 controls the time when the positive terminal of the DC voltage source component is connected to the simulation switching circuit, because only when an arc is generated between the switch contacts... When an arc voltage is generated between the switch contacts, the initial state parameter of circuit breaker component Z5 is set to 0, indicating an open state. This means that when no arc is generated between the switch contacts, the positive terminal of the DC voltage source is not connected to the simulation switching circuit. All other built-in parameters are set to their default values. The DC voltage source component is used to simulate the arc voltage when an arc is generated between the switch contacts. Its built-in parameter voltage amplitude is set according to the actual arc voltage generated between the switch contacts in the actual test. The ideal switch component b is used to control the time when the negative terminal of the DC voltage source component is connected to the simulation switching circuit. Because the arc voltage is only introduced into the switching circuit when an arc is generated between the switch contacts, the initial state parameter of ideal switch component b is set to 0, indicating an open state. This means that when no arc is generated between the switch contacts, the negative terminal of the DC voltage source is not connected to the simulation switching circuit. All other built-in parameters are set to their default values.

[0071] (2) The connection position of the arc voltage equivalent module in the entire simulation switching circuit mainly depends on the location of the fault related to the abnormal electrical waveform in the second stage. The positive terminal of the arc voltage equivalent module needs to be connected to the negative terminal of the switch component that may cause the fault in the second stage. The negative terminal of the arc voltage equivalent module needs to be connected to the positive terminal of another circuit component after the switch component that may cause the fault in the second stage. That is, the arc voltage equivalent module needs to be connected in series with the switch component that may cause the fault in the second stage in the entire simulation switching circuit. The action and timing control of each component in the arc voltage equivalent module need to be determined by the specific fault type to be simulated by the module. Here, we only take the two fault types of arc generation between switch contacts and arc generation between contacts when the switch is closed and the current naturally passes through 0 before the contact is fully closed and the bounce is not over, to introduce the simulation of on-load tap changer switching fault by the arc voltage equivalent module. However, the use of the arc voltage equivalent module is not limited to these two faults.

[0072] When simulating the fault type of arc generation between switch contacts using the arc voltage equivalent module, at the moment when the arc begins to generate between the switch contacts, the state parameter of ideal switch component a is changed from 1 to 0, and a tripping action is performed, so that the branch containing the DC voltage source component starts to function in the simulation switching circuit; at the same time, the state parameters of ideal switch component b and circuit breaker component Z5 are changed from 0 to 1, and a closing action is performed, so that the positive and negative terminals of the DC voltage source are connected, and the simulation of arc voltage between switch contacts begins; after a certain period of time, at the moment when the arc between the switch contacts is extinguished, the state parameter of ideal switch component a is changed from 0 to 1, and a closing action is performed, so that the branch containing the DC voltage source component is short-circuited; at the same time, the state parameters of ideal switch component b and circuit breaker component Z5 are changed from 1 to 0, and a tripping action is performed, so that the DC voltage source is disconnected from the simulation switching circuit;

[0073] When simulating the arc generation between contacts during switch closing bounce using an arc voltage equivalent module, and considering the fault type where the current naturally crosses zero before the contacts are fully closed, at the initial moment of arc generation between the switch closing bounce contacts, the state parameter of ideal switch component a is changed from 1 to 0, executing a tripping action, causing the branch containing the DC voltage source component to start functioning in the simulated switching circuit. Simultaneously, the state parameters of ideal switch component b and circuit breaker component Z5 are changed from 0 to 1, executing a closing action, connecting the positive and negative terminals of the DC voltage source, and starting to simulate the arc voltage between the switch contacts. Immediately afterwards, the state parameter of circuit breaker component Z5 is changed from 1 to 0, executing a tripping action. Because the circuit breaker component can only truly trip successfully when the current flowing through it crosses zero, after a certain time following Z5's tripping operation, when the current flowing through Z5 crosses zero, Z5 truly trips and creates a break in the branch containing the DC voltage source. However, at this time, ideal switch component a is still in the tripped state, equivalent to this... The second closing bounce did not end, and the current flowing through the branch containing the DC voltage source was 0, creating a break. This simulates the fault situation where an arc is generated between the contacts during the switch closing bounce, and the current flowing through the contact gap naturally passes 0 before the bounce ends and the contacts close, extinguishing the arc. Subsequently, due to the switch contacts closing or the recovery voltage across the contacts breaking down the contact gap, the status parameter of circuit breaker component Z5 changes from 0 to 1 for a short period after the circuit breaker component Z5 successfully trips. When the switch closes, the branch containing the DC voltage source is connected. This means that after the switch contacts close or the arc is extinguished, the gap between the contacts is broken down by the recovery voltage at both ends of the break, and the original break is connected. After a certain period of time, when the switch closing bounce is completely finished, the state parameter of the ideal switch component a is changed from 0 to 1, and the closing action is performed to short-circuit the branch containing the DC power supply. At the same time, the state parameters of the ideal switch component b and the circuit breaker component Z5 are changed from 1 to 0, and the DC voltage source is disconnected from the simulation switching circuit.

[0074] The constructed arc voltage equivalent module is connected in series with the switch that may fail, located in the second stage, in the simulation switching circuit. The arc voltage equivalent module is also connected in series in the same position in the simulation switching circuit for the auxiliary phase switching core. Then, the simulation is started to obtain the simulated electrical waveforms of the N-side and N+1-side of the main phase switching core, considering the possible faults caused by the abnormal electrical waveforms during the test. The obtained simulated electrical waveforms considering the possible faults caused by the abnormal electrical waveforms during the test are compared with the actual abnormal electrical waveforms. If the two are similar and their waveform characteristics match well, the location and analysis of the fault corresponding to the abnormal electrical waveforms during the test in the second stage can be verified, providing a clear direction and theoretical support for fault resolution during on-load tap changer switching. Figure 20 and Figure 21As shown, the present invention provides a system for fault diagnosis of on-load tap changer circuit, comprising: a waveform acquisition module, a simulation timing modification module, a preliminary fault location analysis module, a fault simulation module, and a fault verification module;

[0075] Specifically, the waveform acquisition module acquires abnormal electrical waveforms from the actual test of the on-load tap changer switching circuit; the power supply module starts simulation to obtain simulated electrical waveforms for the N-side and N+1-side of the main test phase switching core circuit; the simulation timing modification module compares the abnormal electrical waveforms with the simulated electrical waveforms, modifies the switching action times of the first main switch MC1 and the second main switch MC2, and synchronously adjusts the action times of all other switching components in the switching core module according to the start action times of the first main switch MC1 and the second main switch MC2, to obtain simulated electrical waveforms with phase consistent with the abnormal electrical waveforms; preliminary fault location is performed. The analysis module compares the abnormal electrical waveform with a simulated electrical waveform that has the same phase, and preliminarily locates and analyzes the fault reflected by the abnormal electrical waveform. The fault simulation module connects the arc voltage equivalent module in series to the main test phase switching core circuit and the auxiliary test phase switching core circuit, respectively, to simulate the fault reflected by the abnormal electrical waveform, and obtains a simulated electrical waveform that considers the fault reflected by the abnormal electrical waveform. The fault verification module compares the simulated electrical waveform that considers the fault reflected by the abnormal electrical waveform with the abnormal electrical waveform. If the two waveforms are similar and their waveform characteristics match, the verification of the fault reflected by the abnormal electrical waveform is completed.

[0076] An electronic device, such as Figure 22 As shown, it includes a memory, a processor, and a computer program stored in the memory and executable in the processor. When the processor executes the computer program, it implements the steps of the on-load tap changer circuit fault diagnosis method.

[0077] A computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the on-load tap changer circuit fault diagnosis method.

[0078] This invention first proposes a simulation model for an on-load tap changer switching circuit. This model can simulate and recreate the entire switching process of the on-load tap changer and monitor the voltage and current data of each switching component in the on-load tap changer switching core. By comparing the simulated on-load tap changer switching electrical waveform obtained from this model with the experimental abnormal electrical waveform under the same phase conditions, preliminary location and analysis of the fault corresponding to the experimental abnormal electrical waveform can be achieved. Secondly, this invention proposes an arc voltage equivalent module for simulating on-load tap changer switching faults. By connecting this module in series with the previously identified switches that may cause faults in the switching circuit simulation model, and simulating the relevant faults of the experimental abnormal electrical waveform, a simulated electrical waveform considering the relevant faults of the experimental abnormal electrical waveform can be obtained. Comparing this waveform with the experimental abnormal electrical waveform verifies the location and analysis of the relevant faults in the previous step, providing a clear direction for fault resolution during the on-load tap changer switching process and offering more robust theoretical support.

[0079] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. This description is intended to explain the present invention and not to limit it. It should be noted that the terms "comprising" and "having," and any variations thereof, in the specification and claims of the present invention are intended to cover a non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, systems, products, or devices.

[0080] The specific implementation of this invention consists of four stages. First, the simulation switching circuit is run, and the obtained simulated switching electrical waveform is compared with the electrical waveform under normal switching in the experiment to verify the accuracy of the on-load tap changer switching circuit simulation model. Second, the abnormal electrical waveforms found in the experiment are compared with the simulated electrical waveforms under the same phase conditions, and the possible faults corresponding to the abnormal electrical waveforms in the experiment are preliminarily located and analyzed by referring to the switching sequence of each switch in the switching core. Third, the fault of the abnormal electrical waveform located in the experiment in the second stage is simulated using the arc voltage equivalent module to obtain the simulated electrical waveform that takes the fault into account, and it is compared with the abnormal electrical waveform in the experiment to verify the location and analysis of the fault related to the abnormal electrical waveform in the second stage. Fourth, in the on-load tap changer switching circuit simulation model, the voltage and current waveforms of each switching component of the main test phase during the simulated switching process are obtained to verify that this patent can support the monitoring of voltage and current data of each switching component in the on-load tap changer switching core.

[0081] (1) First step: Verify the accuracy of the switching circuit simulation model.

[0082] The on-load tap changer switches from the N side to the N+1 side and back again during the switching process. Therefore, the bidirectional switching function of the switching circuit simulation model needs to be verified in this step.

[0083] For switching from the N side to the N+1 side, the initial state parameters of each switching component in the switching core module of the simulation switching circuit are set as follows: the initial state parameter of the left side Z11 of the first changeover switch Z1 is 1, the initial state parameter of the right side Z12 of the first changeover switch Z1 is 0, the initial state parameter of the main vacuum bulb V1 is 1, the initial state parameter of the first main switch MC1 is 1, the initial state parameter of the first auxiliary vacuum bulb V2 is 0, the initial state parameter of the first auxiliary vacuum bulb V3 is 0, the initial state parameter of the left side Z21 of the second changeover switch Z2 is 1, the initial state parameter of the right side Z22 of the second changeover switch Z2 is 0, the initial state parameter of the second main switch MC2 is 0, and the initial state parameters of each switch of the auxiliary phase are the same as those of the main phase; the initial state parameter of the three-phase circuit breaker Z0 is 0; the initial state parameter of the current-limiting resistor control switch Z3 is 1, and the initial state parameter of the current-limiting resistor control switch Z4 is 0.

[0084] The timing sequence of each switch in the simulation switching circuit is imported as follows: At 0s, the instant the simulation starts, the state parameter of the three-phase circuit breaker Z0 changes from 0 to 1, turning on the entire simulation switching circuit; when the current generated by the LC resonant module in the simulation switching circuit tends to stabilize, at 0.5s, the state parameter of the current-limiting resistor control switch Z3 changes from 1 to 0, and the state parameter of the current-limiting resistor control switch Z4 changes from 0 to 1, introducing a 0.25Ω current-limiting resistor into the circuit; at 1.01s, the state parameter of the first main switch MC1 changes from 1 to 0, executing the opening action; at 1.03s, the state parameters of the first auxiliary vacuum bulb V2 and the second auxiliary vacuum bulb V3 simultaneously change from 0 to 1, executing the closing action; at 1.035s, the state parameter of the main vacuum bulb V1 changes from 1 to 0, executing the opening action; at 1.0... At 5s, the state parameter of Z11 on the left side of the first transfer switch Z1 changes from 1 to 0, executing a tripping action; at 1.055s, the state parameter of Z12 on the right side of the first transfer switch Z1 changes from 0 to 1, executing a closing action; at 1.070s, the state parameter of the main vacuum bulb V1 changes from 0 to 1, executing a closing action; at 1.075s, the state parameters of the first auxiliary vacuum bulb V2 and the second auxiliary vacuum bulb V3 simultaneously change from 1 to 0, executing a tripping action; at 1.090s, the state parameter of Z21 on the left side of the second transfer switch Z2 changes from 1 to 0, executing a tripping action; at 1.095s, the state parameter of the second main switch MC2 changes from 0 to 1, executing a closing action; at 1.1s, the state parameter of Z22 on the right side of the second transfer switch Z2 changes from 0 to 1, executing a closing action. This completes the switching process of the on-load tap changer simulation circuit from the N side to the N+1 side in one operation.

[0085] The voltage and current waveforms of the N-side and N+1-side switches during the entire switching process were derived from the simulation circuit model and compared with the voltage and current waveforms of the N-side and N+1-side switches when the on-load tap changer switches from the N-side to the N+1-side in the actual experiment. The specific comparison is as follows: Figure 7 and Figure 8 As shown, under the same phase conditions, the waveform characteristics of the simulated waveform and the experimental waveform can match well, verifying that the on-load tap changer switching circuit simulation model can switch the load from the N side to the N+1 side in a way that is consistent with the actual on-load tap changer product.

[0086] For switching from the N+1 side to the N side, the initial state parameters of each switch component in the switching core module of the simulation switching circuit are set as follows: the initial state parameter of Z11 on the left side of the first changeover switch Z1 is 0, the initial state parameter of Z12 on the right side of the first changeover switch Z1 is 1, the initial state parameter of the main vacuum bulb V1 is 1, the initial state parameter of the first main switch MC1 is 0, the initial state parameter of the first auxiliary vacuum bulb V2 is 0, the initial state parameter of the first auxiliary vacuum bulb V3 is 0, the initial state parameter of Z21 on the left side of the second changeover switch Z2 is 0, the initial state parameter of Z22 on the right side of the second changeover switch Z2 is 1, the initial state parameter of the second main switch MC2 is 1, and the initial state parameters of each switch in the auxiliary phase switching core are the same as those in the main phase switching core; the initial state parameter of the three-phase circuit breaker Z0 is 0; the initial state parameter of the current-limiting resistor control switch Z3 is 1, and the initial state parameter of the current-limiting resistor control switch Z4 is 0.

[0087] The timing sequence of each switch in the simulation switching circuit is imported as follows: At 0s, the instant the simulation starts, the state parameter of the three-phase circuit breaker Z0 changes from 0 to 1, turning on the entire simulation switching circuit; when the current generated by the LC resonant module in the simulation switching circuit tends to stabilize, at 0.5s, the state parameter of the current-limiting resistor control switch Z3 changes from 1 to 0, and the state parameter of the current-limiting resistor control switch Z4 changes from 0 to 1, introducing a 0.25Ω current-limiting resistor into the circuit; at 1.01s, the state parameter of the first main switch MC2 changes from 1 to 0, executing the opening action; at 1.03s, the state parameters of the first auxiliary vacuum bulb V2 and the second auxiliary vacuum bulb V3 simultaneously change from 0 to 1, executing the closing action; at 1.035s, the state parameter of the main vacuum bulb V1 changes from 1 to 0, executing the opening action; at 1.0... At 5s, the state parameter of Z12 on the right side of the first transfer switch Z1 changes from 1 to 0, executing the opening action; at 1.055s, the state parameter of Z11 on the left side of the first transfer switch Z1 changes from 0 to 1, executing the closing action; at 1.070s, the state parameter of the main vacuum bulb V1 changes from 0 to 1, executing the closing action; at 1.075s, the state parameters of the first auxiliary vacuum bulb V2 and the second auxiliary vacuum bulb V3 simultaneously change from 1 to 0, executing the opening action; at 1.090s, the state parameter of Z22 on the right side of the second transfer switch Z2 changes from 1 to 0, executing the opening action; at 1.095s, the state parameter of the second main switch MC1 changes from 0 to 1, executing the closing action; at 1.1s, the state parameter of Z21 on the left side of the second transfer switch Z2 changes from 0 to 1, executing the closing action. This completes the on-load tap changer simulation switching circuit's one-time switching of the load from the N+1 side to the N side.

[0088] The voltage and current waveforms of the N-side and N+1-side switches during the entire switching process were derived from the simulation circuit model and compared with the voltage and current waveforms of the N-side and N+1-side switches when the on-load tap changer switches from the N+1-side to the N-side in the actual test. The specific comparison is as follows: Figure 9 and Figure 10 As shown, under the same phase conditions, the waveform characteristics of the simulated waveform and the experimental waveform can match well, verifying that the on-load tap changer switching circuit simulation model can switch the load from the N+1 side to the N side in a way that is consistent with the actual on-load tap changer product.

[0089] This verifies that the functions of the on-load tap changer switching circuit simulation model when switching from the N side to the N+1 side and from the N+1 side to the N side are consistent with the actual on-load tap changer product, and the simulation model of the switching circuit is considered to be accurate.

[0090] (2) Second step: Compare the test abnormal electrical waveform with the simulated electrical waveform under the same phase conditions to achieve preliminary location and analysis of the fault related to the test abnormal electrical waveform.

[0091] Two abnormal electrical waveforms were selected from the test abnormal electrical waveforms as examples for specific implementation in this section. These two abnormal electrical waveforms are referred to as test abnormal electrical waveform 1 and test abnormal electrical waveform 2, respectively. It should be noted that the scope of application of the embodiments of the present invention in this section is by no means limited to these two abnormal waveforms.

[0092] For abnormal electrical waveform 1: Abnormal electrical waveform 1 is the test electrical waveform diagram when the on-load tap changer switches from the N+1 side to the N side. It is found that the N-side voltage Un is... Figure 11 After the voltage drops to 0 at time t1, an abnormal voltage spike appears in region A, followed by an immediate drop to 0 and a period near 0. This is compared with the simulated electrical waveform under normal switching conditions from N+1 to N, under the same phase conditions. See [link to comparison details] for more information. Figure 11 and Figure 12 . Reference Figure 4 When switching from the N+1 side gear to the N side gear, the timing sequence of the operation of each switching component in the switching core is changed. Figure 11 The abnormal voltage spike in region A occurred after the main vacuum bulb V1 closed, and the peak value of this abnormal voltage spike followed a sinusoidal trajectory of Un over time. Furthermore, the N-side current In at the corresponding moment of this abnormal voltage spike was also 0. Therefore, a preliminary fault location and analysis of the abnormal electrical waveform 1 was performed, leading to the following judgment: The main vacuum bulb V1 bounced upon closing, generating an arc between the contacts. However, before the bounce of V1 ended and the contacts closed, the current flowing through V1 naturally passed zero, extinguishing the arc and forming a break. A recovery voltage was generated across the V1 break, forming... Figure 11 An abnormal voltage spike occurs in region A. Subsequently, the V1 contact closes or the V1 contact gap is broken down by the recovery voltage at both ends of the break, causing the break to conduct, which makes Un quickly become 0 after experiencing the abnormal voltage spike.

[0093] For test abnormal electrical waveform 2: Test abnormal electrical waveform 2 is the test electrical waveform diagram when the on-load tap changer switches from the N+1 side to the N side, in which the N side voltage Un is found to be... Figure 13 After the voltage drops to 0 at time t2, it increases back up to over 1000 volts, as shown in region B of the diagram. This is compared with the simulated electrical waveform of a normal switch from the N+1 side to the N side under the same phase conditions. See [link to comparison details] for more information. Figure 13 and Figure 14 . Reference Figure 4 When switching from the N+1 side gear to the N side gear, the timing sequence of the operation of each switching component in the switching core is changed. Figure 13 The abnormal reverse increase of Un in area B almost occurs simultaneously with V1 closing. If V1 closing and bouncing generates an arc between the contacts, the resulting vacuum arc voltage would be around 20V, which is inconsistent with this abnormal phenomenon. Because the arc voltage in insulating oil can reach thousands of volts, it is determined that this phenomenon is related to the arc generated by the switch in the insulating oil. From... Figure 4 It can be seen that the previous action of the switching core before V1 closes is the closing of the left side Z11 of the first changeover switch Z1. Z1 is located in the insulating oil. If an arc is generated at Z1, the arc voltage will be over 1,000 volts. Therefore, based on the above analysis, the corresponding fault of the abnormal electrical waveform 2 in the test was initially located and analyzed, and the following judgment was made: In the abnormal electrical waveform 2 in the test, the abnormal phenomenon that the N-side voltage Un becomes 0 at the moment V1 closes and then increases to over 1,000 volts is caused by the simultaneous closing and conduction of the N-side circuit when V1 closes, and the left side Z11 of the changeover switch Z1 closes and bounces, generating an arc in the insulating oil.

[0094] (3) Third step: Use the arc voltage equivalent module to simulate the relevant faults of the abnormal electrical waveforms in the test located in the second step, and compare the simulated electrical waveforms considering the faults with the abnormal electrical waveforms in the test to verify the location and analysis of the relevant faults of the abnormal electrical waveforms in the second step.

[0095] Regarding the abnormal electrical waveform 1 in the test: Since the preliminary fault location and analysis of the abnormal electrical waveform 1 in the test is that the current flowing through V1 is zero during the arc generation process of the main vacuum bulb V1 closing and bouncing, the arc voltage equivalent module is first connected in series with the main vacuum bulb V1 in the simulation switching circuit. The positive terminal of the arc voltage equivalent module is connected to the negative terminal of the circuit breaker component V1, and the negative terminal is connected to the neutral point of the switching core. The connection is as follows: Figure 15 As shown.

[0096] In the arc voltage equivalent module, the initial state parameter of ideal switch component a is set to 1, indicating a closed state, representing a short circuit in the branch containing the DC voltage source; the initial state of ideal switch component b is 0, indicating an open state, representing that the negative terminal of the DC voltage source component is not connected to the circuit; the initial state of circuit breaker component Z5 is 0, indicating an open state, representing that the positive terminal of the DC voltage source component is not connected to the circuit; the voltage amplitude parameter of the DC voltage source is set to positive 20V, based on the fact that the amplitude of the vacuum arc voltage generated in the main vacuum bulb V1 is approximately 20V, and the current flowing through V1 during the closing bounce at this time is positive, resulting in a relatively positive arc voltage. Next, based on the specific closing time of the main vacuum bulb V1 in the simulated electrical waveform consistent with the phase condition of the experimental abnormal electrical waveform 1 in the second stage, the action sequence of each component in the arc voltage equivalent module is set. In the simulated electrical waveform, V1 closes at 1.078s. Based on this, the operating times of each switch in the arc voltage equivalent module are set as follows: 1.079s, ideal switch component a opens, introducing the branch containing the DC voltage source component into the simulated switching circuit. Simultaneously, circuit breaker component Z5 and ideal switch component b close, connecting the positive and negative terminals of the DC voltage source component, and starting to simulate the arc voltage generated when the main vacuum tube V1 bounces; 1.0792s, circuit breaker component Z5 opens. In the simulated electrical waveform, it can be seen that the current flowing through circuit breaker Z5 crosses zero at 1.08s. 5. The current interruption was successful, creating a break in the branch where the DC voltage source is located. This simulates the arcing process during V1 closing bounce, where the current flowing through V1 naturally crosses zero, extinguishing the arc. At 1.0805s, circuit breaker assembly Z5 is closed, indicating that the break created after V1 contacts close or V1 arc extinguishing is broken down by the restored voltage, and V1 conducts. At 1.081s, ideal switch assembly a is closed, short-circuiting the branch where the DC voltage source assembly is located. Simultaneously, circuit breaker assembly Z5 and ideal switch assembly b are opened, disconnecting the DC voltage source assembly from the simulated switching circuit, indicating the end of V1 closing bounce. At this point, the simulation of the fault related to abnormal electrical waveform 1 is complete. The voltage and current waveforms of the N-side and N+1-side switches of the switching core are read from the switching circuit simulation model throughout the switching process and compared with abnormal electrical waveform 1. The comparison is as follows: Figure 11 and Figure 16 As can be seen, the simulated switching electrical waveform considering the fault related to the experimental abnormal electrical waveform 1 is extremely similar to the experimental abnormal electrical waveform 1. Except for the waveform abnormalities in regions A and A', which are very similar, the two waveforms are quite similar in other details. Figure 11 and Figure 12 The comparison results are also better matched, so the location and analysis of the fault related to the abnormal electrical waveform 1 in the second step can be verified, and the abnormality of the abnormal electrical waveform 1 in the test can be confirmed. The cause of the abnormality of the abnormal electrical waveform 1 is that during the process of V:1 closing bounce generating an arc, the current flowing through V1 is 0, a break is formed between the contacts of V1, and a recovery voltage with a high amplitude is generated at both ends of the break.

[0097] Regarding the abnormal electrical waveform 2 in the experiment: The initial fault location and analysis of the abnormal electrical waveform 2 is that, simultaneously with the closing of the main vacuum bulb V1 switching core N-side conduction, the left side of the first changeover switch Z1, Z11, bounces and arcs in the oil. Therefore, the arc voltage equivalent module is first connected in series with the circuit breaker assembly Z11 in the simulation switching circuit. The positive terminal of the arc voltage equivalent module is connected to the negative terminal of the circuit breaker assembly Z11, and the negative terminal is connected to the positive terminal of the main vacuum bulb V1. The connection is as follows: Figure 17 As shown.

[0098] In the arc voltage equivalent module, the initial state parameter of ideal switch component a is set to 1, indicating a closed state, representing a short circuit in the branch containing the DC voltage source; the initial state of ideal switch component b is 0, indicating an open state, representing that the negative terminal of the DC voltage source component is not connected to the circuit; the initial state of circuit breaker component Z5 is 0, indicating an open state, representing that the positive terminal of the DC voltage source component is not connected to the circuit; the voltage amplitude parameter of the DC voltage source is set to -2000V, based on the fact that switch Z11 is in insulating oil, the arc voltage amplitude in the oil is around 2000V, and the current flowing through Z11 during the closing bounce at this time is negative, resulting in a relatively negative arc voltage. Next, based on the specific closing time of the main vacuum bulb V1 in the simulated electrical waveform consistent with the phase condition of the experimental abnormal electrical waveform 2 in the second stage, the action sequence of each component in the arc voltage equivalent module is set. In the simulated electrical waveform, V1 closes at 1.066s. Based on this, the action times of each switch in the arc voltage equivalent module are set as follows: 1.067s, ideal switch component a opens, introducing the branch containing the DC voltage source component into the simulated switching circuit. Simultaneously, circuit breaker component Z5 and ideal switch component b close, connecting the positive and negative terminals of the DC voltage source component, starting the simulation of the arc voltage generated when Z11 bounces. When Z11 finishes bouncing, at 1.069s, ideal switch component a closes, short-circuiting the branch containing the DC voltage source component. Simultaneously, circuit breaker component Z5 and ideal switch component b open, disconnecting the DC voltage source component from the simulated switching circuit, representing the end of the arc generation process of Z11 closing and bouncing in oil. At this point, the simulation of the fault related to the abnormal electrical waveform 2 is complete. The voltage and current waveforms of the switching core's N-side and N+1-side stops during the entire switching process are read from the switching circuit simulation model and compared with the abnormal electrical waveform 2. The comparison is as follows: Figure 13 and Figure 18 As can be seen, the simulated switching electrical waveform considering the fault related to the experimental abnormal electrical waveform 2 is extremely similar to the experimental abnormal electrical waveform 2. Except for the waveform abnormalities in regions B and B', which are very similar, the two waveforms are quite similar in other waveform details. Figure 13 and Figure 14The comparison results are also better matched, so the location and analysis of the fault related to the abnormal electrical waveform 2 in the second step can be verified, and the abnormal cause of the abnormal electrical waveform 2 is confirmed: when the N side circuit of V1 is closed, the left side part Z11 of the first changeover switch Z1 bounces and generates an electric arc in the oil.

[0099] (4) Fourth step: In the simulation model of the on-load tap changer switching circuit, the voltage and current data of each switching component of the main test phase switching core are acquired to verify that this patent can support the monitoring of the voltage and current data of each switching component in the on-load tap changer switching core.

[0100] In the switching circuit simulation model, voltage and current sensors are added to all switching components in the main test phase switching core. These sensors are then connected to an oscilloscope assembly in the simulation model. The simulation is then started, and detailed voltage and current data for each switching component in the main test phase during the simulation switching process can be obtained from the oscilloscope assembly. The voltage and current monitoring of some major switching components in the main test phase switching core during a single on-load tap changer switching from the N side to the N+1 side is shown below. Figure 19 As shown, Iv1 and Uv1 are the current flowing through the main vacuum bulb V1 and the voltage across its terminals, Iv2 and Uv2 are the current flowing through the first auxiliary vacuum bulb V2 and the voltage across its terminals, and Iz11 and Uz11 are the current flowing through the left side Z11 of the first changeover switch Z1 and the voltage across its terminals. Figure 19 The simulation only shows the voltage and current monitoring of some switching components in the on-load tap changer core, but the monitoring of voltage and current data in the switching circuit simulation model is by no means limited to this. Figure 19 The switching components shown in the model can all have their voltage and current data monitored. This verifies that the on-load tap changer simulation model built in this invention supports monitoring all switching components in the switching core during the switching process.

[0101] This concludes the specific implementation of the present invention. In the first stage, the on-load tap changer switching circuit simulation model constructed by the present invention accurately reproduced the entire process of the on-load tap changer during actual switching. In the second stage, using the constructed on-load tap changer switching circuit simulation model, a simulated electrical waveform with the same phase conditions as the experimental abnormal electrical waveform was found. By comparing the waveforms and the switching sequence of each switch in the switching core, the preliminary location and analysis of the faults related to the experimental abnormal electrical waveform were achieved. In the third stage, using the arc voltage equivalent module constructed based on the on-load tap changer switching circuit simulation model of the present invention, the two experimental abnormal electrical waveforms in the second stage were successfully simulated, verifying the location and analysis of the faults related to the two experimental abnormal electrical waveforms in the second stage. In the fourth stage, the voltage and current waveforms of all switching components of the main test phase switching core of the on-load tap changer were derived from the on-load tap changer switching circuit simulation model, verifying that the on-load tap changer switching circuit simulation model constructed by the present invention can support the monitoring of voltage and current data of all switching components inside the on-load tap changer. In summary, the following conclusions can be drawn: This invention is indeed an effective means for research on the on-load tap changer switching process, can provide a clear direction for troubleshooting during the on-load tap changer switching process, and can provide more theoretical support for improving the lifespan of on-load tap changers.

[0102] As is known from common technical knowledge, the present invention can be implemented through other embodiments that do not depart from its spirit or essential characteristics. Therefore, the disclosed embodiments described above are merely illustrative in all respects and are not the only ones; all modifications within the scope of the present invention or equivalent to the scope of the present invention are included in the present invention.

Claims

1. A load tap changer switching circuit, characterized by, include: The power supply module, transformer module, switching core module, LC resonant module, and current-limiting resistor module include: A power supply module, connected to the transformer module, is used to control the opening and closing of the on-load tap changer switching circuit; A transformer module, connected to the switching core module and the current-limiting resistor module, is used to regulate the voltage of the power supply module; The switching core module is connected to the LC resonant module to adjust the voltage ratio of the transformer module or to switch the on-load tap changer circuit. An LC resonant module, connected to a current-limiting resistor module, is used to generate power frequency current in the on-load tap changer switching circuit, while avoiding the impact of sudden current changes in the switching core module on the transformer module during the switching process. A current-limiting resistor module is used to limit the unstable current generated by the LC resonant module; An arc voltage equivalent module, connected to the switching core module, is used to simulate and verify the faults of the on-load tap changer switching circuit during the switching process. The arc voltage equivalent module includes: a DC voltage source component, a circuit breaker component, an ideal switch component b, and an ideal switch component a. The positive terminal of the DC voltage source component is connected to the negative terminal of the circuit breaker component, the negative terminal of the DC voltage source component is connected to the positive terminal of the ideal switch component b, the positive terminal of the ideal switch component a is connected to the positive terminal of the circuit breaker component, and the negative terminal of the ideal switch component a is connected to the negative terminal of the ideal switch component b. The switching core module includes: a main test phase switching core circuit and a supporting test phase switching core circuit; The main test phase switching core circuit includes: a main test phase switching core, a first changeover switch Z1, a second changeover switch Z2, a main vacuum bulb V1, a first auxiliary vacuum bulb V2, a second auxiliary vacuum bulb V3, a transition resistor R, a first main switch MC1, and a second main switch MC2; the N-side of the main test phase switching core is connected to the positive terminal of the Z11 terminal of the first changeover switch Z1, and the N+1 side of the main test phase switching core is connected to the positive terminal of the Z12 terminal of the first changeover switch Z1; The positive terminal of the Z21 end of the second changeover switch Z2 is connected to the negative terminal of the first auxiliary vacuum bulb V2, and the positive terminal of the Z22 end of the second changeover switch Z2 is connected to the negative terminal of the second auxiliary vacuum bulb V3. The positive electrode of the main vacuum bulb V1 is connected to the negative electrodes of Z11 and Z12, and the negative electrode of the main vacuum bulb V1 is connected to the neutral point of the main test phase switching core. The positive electrode of the first auxiliary vacuum bulb V2 is connected to the N-side stop of the main test phase switching core; The positive electrode of the second auxiliary vacuum bulb V3 is connected to the N+1 side stop of the main test phase switching core; The positive terminal of the transition resistor R is connected to the negative terminals of terminals Z21 and Z22, and the negative terminal of the transition resistor R is connected to the neutral point of the main test phase switching core. The positive terminal of the first main switch MC1 is connected to the N-side stop of the main test phase switching core, and the negative terminal of the first main switch MC1 is connected to the neutral point of the main test phase switching core. The positive terminal of the second main switch MC2 is connected to the N+1 side stop of the main test phase switching core, and the negative terminal of the second main switch MC2 is connected to the neutral point of the main test phase switching core; The structure of the accompanying phase switching core circuit is the same as that of the main phase switching core circuit.

2. A load tap changer switching circuit according to claim 1, characterized in that, The power module includes a three-phase power supply component, a three-phase voltage and current measurement component, and a three-phase circuit breaker component. The three-phase power supply component is connected to the three-phase voltage and current measurement component, and the three-phase circuit breaker component is connected to the three-phase power supply component and the transformer module. The transformer module includes a single-phase transformer assembly.

3. The on-load tap changer switching circuit according to claim 1, characterized in that, The LC resonant module includes an inductor component and a capacitor component. The positive terminal of the inductor component is connected to the neutral point of the main test phase switching core, the positive terminal of the capacitor component is connected to the neutral point of the auxiliary test phase switching core, and the negative terminal of the inductor component is connected to the negative terminal of the capacitor component.

4. The on-load tap changer switching circuit according to claim 1, characterized in that, The current-limiting resistor module includes: current-limiting resistor R2, current-limiting resistor R3, circuit breaker assembly Z3, and circuit breaker assembly Z4; The current-limiting resistors R2 and R3 are connected in parallel, the current-limiting resistor R2 is connected in series with the circuit breaker assembly Z3, the current-limiting resistor R3 is connected in series with the circuit breaker assembly Z4, and the resistance of the current-limiting resistor R2 is greater than the resistance of the current-limiting resistor R3.

5. A method for diagnosing faults in an on-load tap changer circuit, characterized in that, The on-load tap changer switching circuit according to claim 1 includes the following steps: Obtain abnormal electrical waveforms from the actual test of the on-load tap changer switching circuit; start the power supply module to begin simulation and obtain the simulated electrical waveforms of the N-side and N+1-side of the main test phase switching core circuit; The abnormal electrical waveform and the simulated electrical waveform are compared, and the switching action times of the first main switch MC1 and the second main switch MC2 are modified. The action times of all other switching components in the switching core module are synchronously adjusted according to the start action times of the first main switch MC1 and the second main switch MC2 to obtain a simulated electrical waveform with the same phase as the abnormal electrical waveform. By comparing the abnormal electrical waveform with the simulated electrical waveform that has the same phase, the fault reflected by the abnormal electrical waveform can be preliminarily located and analyzed. The arc voltage equivalent module is connected in series to the main test phase switching core circuit and the auxiliary test phase switching core circuit respectively to simulate the fault reflected by the abnormal electrical waveform and obtain a simulated electrical waveform that takes into account the fault reflected by the abnormal electrical waveform. By comparing the simulated electrical waveform reflecting the fault with the abnormal electrical waveform, if the two waveforms are similar and their waveform characteristics match, the verification of the fault reflected by the abnormal electrical waveform is completed.

6. A system for diagnosing faults in an on-load tap changer circuit, characterized in that, The fault diagnosis method according to claim 5 includes: The waveform acquisition module is used to acquire abnormal electrical waveforms in the actual test of the on-load tap changer switching circuit; the power supply module is started to begin simulation and obtain the simulated electrical waveforms of the N-side and N+1-side of the main test phase switching core circuit; The simulation timing modification module is used to compare the abnormal electrical waveform with the simulated electrical waveform, modify the switching action time of the first main switch MC1 and the second main switch MC2, and synchronously adjust the action time of all other switching components in the switching core module according to the start action time of the first main switch MC1 and the second main switch MC2, so as to obtain a simulated electrical waveform that is consistent with the phase of the abnormal electrical waveform. The preliminary fault location analysis module is used to compare abnormal electrical waveforms with simulated electrical waveforms that have the same phase, and to preliminarily locate and analyze the fault reflected by the abnormal electrical waveforms. The fault simulation module is used to connect the arc voltage equivalent module in series to the main test phase switching core circuit and the auxiliary test phase switching core circuit respectively to simulate the fault reflected by the abnormal electrical waveform and obtain a simulated electrical waveform that takes into account the fault reflected by the abnormal electrical waveform. The fault verification module is used to compare the simulated electrical waveform reflecting the fault, which takes into account the abnormal electrical waveform, with the abnormal electrical waveform. If the two waveforms are similar and their waveform characteristics match, the verification of the fault reflected by the abnormal electrical waveform is completed.

7. An electronic device, characterized in that, It includes a memory, a processor, and a computer program stored in the memory and executable in the processor, wherein the processor executes the computer program to implement the steps of the on-load tap changer circuit fault diagnosis method of claim 5.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of the on-load tap changer circuit fault diagnosis method of claim 5.

Images