Method and device for detecting interlayer insulation state of dry-type transformer

Abstract

The invention belongs to the technical field of insulation state detection, and particularly relates to a method and device for detecting the interlayer insulation state of a dry-type transformer, and the method comprises the steps: building a layered dry-type transformer simulation analysis model in finite element simulation software; determining resistance values of an interlayer insulation degradation critical state and a collapse critical state of the dry-type transformer through an interlayer insulation fault test; simulating to obtain a sensitive state quantity value in an interlayer insulation degradation critical state and a sensitive state quantity value in an insulation collapse critical state of the dry-type transformer; the voltage and current of the three-phase high-voltage winding and the three-phase low-voltage winding of the dry-type transformer under the actual working condition are collected, the actual sensitive state quantity value of each phase in the operation of the dry-type transformer is calculated, the actual sensitive state quantity value is compared with the simulation value, and the interlayer insulation state of each phase of the detected dry-type transformer is determined. According to the invention, accurate and real-time monitoring and early warning of the interlayer insulation state of the dry-type transformer are realized, the fault risk is effectively reduced, and safe and stable operation of a power system is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of insulation state detection, and in particular relates to a method and device for detecting the interlayer insulation state of a dry-type transformer. Background Art

[0002] As a high-performance power equipment, dry-type transformers offer numerous advantages, including low maintenance, high efficiency, energy conservation and environmental protection, fire resistance, and explosion-proofing. They are widely used in power distribution systems, accounting for nearly 50% of the total transformer usage in these systems. However, during operation, dry-type transformers are subject to frequent inter-winding insulation failures, influenced by factors such as manufacturing process, temperature, humidity, voltage stress, mechanical vibration, and load characteristics. According to relevant statistics, among all types of dry-type transformer failures, the proportion of inter-winding insulation failures has shown an increasing trend year by year, and has become a major threat to the safe and stable operation of dry-type transformers.

[0003] Traditional insulation monitoring methods, mostly based on overall insulation performance assessments, struggle to accurately identify localized interlayer degradation early on. If interlayer insulation faults are not effectively detected and addressed in their early stages, they can rapidly escalate, easily leading to serious accidents such as transformer winding short circuits and burnouts. These can not only cause significant economic losses but can also cause power outages, posing a serious threat to the reliability and stability of the power system. Summary of the Invention

[0004] In view of the above shortcomings in the prior art, the purpose of the present invention is to provide a method and device for detecting the interlayer insulation status of a dry-type transformer. By combining the interlayer insulation fault test with the finite element simulation model, accurate and real-time monitoring and early warning of the interlayer insulation status of the dry-type transformer are achieved, effectively reducing the risk of failure and ensuring the safe and stable operation of the power system.

[0005] To achieve the above objectives, the present invention provides a method for detecting the interlayer insulation state of a dry-type transformer, comprising the following steps: S1. For the dry-type transformer being tested, a layered dry-type transformer simulation analysis model is constructed in the finite element simulation software; S2. Based on the current and voltage transformers and three-phase voltage regulator installed on the dry-type transformer, determine the resistance value of the critical state of interlayer insulation degradation and critical state of collapse of the dry-type transformer through interlayer insulation fault test; S3. Based on the dry-type transformer simulation analysis model, simulate and obtain the sensitive state value of the dry-type transformer interlayer insulation degradation critical state , and the sensitive state value of dry-type transformer interlayer insulation collapse critical state ; S4. Collect the voltage and current of the three-phase high-voltage and low-voltage windings of the dry-type transformer under actual working conditions, and calculate the actual sensitive state value of each phase during the operation of the dry-type transformer ,and and Compare and determine the insulation status between each phase of the dry-type transformer being tested.

[0006] As a preferred embodiment of the present invention, in the S1, the "electromagnetic field-external circuit" coupling in the ANSYS finite element simulation software is used to build a three-dimensional model consistent with the actual transformer, and each phase winding on the high-voltage side of the three-dimensional model is layered according to the actual situation to obtain a dry-type transformer simulation analysis model.

[0007] As a preferred embodiment of the present invention, in said S2, the method for determining the resistance value of the critical state of degradation and the critical state of collapse of the interlayer insulation of the dry-type transformer through the interlayer insulation failure test is: S2.1. Connect the three-phase winding on the high-voltage side of a dry-type transformer to a three-phase voltage regulator. Leave the low-voltage winding open. Connect the taps connecting two adjacent layers of the high-voltage winding of the dry-type transformer via contact resistors to simulate the interlayer insulation resistance under different degrees of insulation degradation. Use current and voltage transformers to monitor the current flowing through the contact resistors and the voltage across them. S2.2. Gradually increase the voltage of the high-voltage winding using a three-phase voltage regulator. Within the maximum current range that the high-voltage winding conductor can withstand, measure the current flowing through the short-circuited turn until the maximum current that the conductor can withstand is reached and then stop increasing the voltage. S2.3. Based on the measured interlayer insulation resistance-fault layer current relationship curve, take the two interlayer insulation resistance values corresponding to the two points with the largest rate of change on the curve as the resistance values of the critical state of interlayer insulation degradation and the critical state of collapse. The larger resistance value is the resistance value of the critical state of interlayer insulation degradation, and the smaller resistance value is the resistance value of the critical state of interlayer insulation collapse.

[0008] As a preferred embodiment of the present invention, the relationship between the insulation resistance between winding layers and the fault layer current is expressed as: ; Where, is the winding fault layer current; is the induced voltage of the winding fault layer; is the winding fault layer resistance; is the interlayer insulation resistance.

[0009] As a preferred embodiment of the present invention, in said S3, based on the resistance value of the critical state of interlayer insulation degradation and the critical state of collapse of the dry-type transformer obtained in S2, the interlayer insulation resistance value of a certain phase winding is set in the external circuit of the dry-type transformer simulation analysis model, and the critical state of interlayer insulation degradation and the critical state of collapse of the phase are simulated accordingly, and the sensitive state quantity value of the critical state of interlayer insulation degradation and the critical state of collapse of the dry-type transformer is determined according to the voltage and current mutation conditions. 、 , and verify 、 The error between the corresponding sensitive state quantity value measured in the interlayer insulation fault test is within the allowable range.

[0010] As a preferred embodiment of the present invention, in said S4, The calculation method is as follows: take the zero-sequence component into account to measure the unbalance, use the difference between the improved voltage and current unbalance as the sensitive state quantity, and standardize the sensitive state quantity into per-unit value: Improve voltage imbalance : ; Improved current imbalance : ; Actual value of sensitive state quantity : ; Will Per-unit value: ; Where, 、 、 Represent the positive sequence, negative sequence and zero sequence voltage components on the high voltage side of the dry-type transformer respectively; 、 、 Represent the positive sequence, negative sequence and zero sequence current components of the high voltage side of the dry-type transformer respectively; 、 、 They represent the normalized positive-sequence, negative-sequence and zero-sequence voltage components on the high-voltage side of the dry-type transformer respectively; 、 、 They represent the normalized positive-sequence, negative-sequence and zero-sequence current components on the high-voltage side of the dry-type transformer respectively.

[0011] As a preferred embodiment of the present invention, in said S4, the method for determining the insulation state of each phase of the dry-type transformer being detected is as follows: When the insulation between layers is normal; when When , the interlayer insulation is in the damage warning state; when When , the interlayer insulation is in a breakdown state.

[0012] As a preferred solution of the present invention, when the interlayer insulation is in a damage warning state, an early warning instruction is issued and a visual output is performed; when the interlayer insulation is in a collapse state, a tripping instruction is issued and a visual output is performed.

[0013] As a preferred embodiment of the present invention, in S5, the voltage and current of the three-phase high-voltage and low-voltage windings of the dry-type transformer under actual working conditions are collected through an information acquisition system. The information acquisition system includes a low-voltage winding voltage / current sensor, a high-voltage winding voltage / current sensor, a signal acquisition unit, a logic analysis unit, a communication unit and a human-machine interface. The low-voltage winding voltage / current sensor and the high-voltage winding voltage / current sensor are respectively installed in the low-voltage winding and high-voltage winding of the dry-type transformer. The output end of each voltage / current sensor is connected to the signal input end of the signal acquisition unit, the output end of the signal acquisition unit is connected to the input end of the logic analysis unit, and the output end of the logic analysis module is connected to the human-machine interface through the communication unit.

[0014] A device for detecting the interlayer insulation state of a dry-type transformer includes a memory, a processor, and a computer program stored in the memory and capable of running on the processor. The method is implemented by executing the computer program by the processor.

[0015] The beneficial effects of the present invention are: By combining interlayer insulation fault testing with finite element simulation models, this method accurately determines the critical and breakdown resistance values of dry-type transformer interlayer insulation. The simulation model then simulates the response curves for different insulation states. Based on this, sensitive state variables during actual operation are calculated and compared with thresholds, enabling precise identification and early warning of good, damaged, and breakdown interlayer insulation states. This effectively addresses the difficulty of traditional detection methods in early identification of localized interlayer degradation, reducing the probability of accidents.

[0016] This invention uses ANSYS simulation software to simulate response curves under different insulation conditions, and compares and verifies this with actual voltage and current data, significantly improving the consistency and reliability of the model with actual operating conditions. Through a modular data acquisition and processing system, this system enables real-time monitoring and analysis of the operating status of dry-type transformers. With a clear structure and a high degree of automation, it is widely applicable to different types of dry-type transformers, demonstrating excellent engineering adaptability and potential for widespread adoption.

[0017] The present invention can not only accurately monitor the insulation status between layers of dry-type transformers, but also issue early warning instructions in time when the insulation is damaged, and issue trip instructions when the insulation collapses, effectively preventing serious accidents such as transformer burning, ensuring the reliability and safety of transformer operation, reducing economic losses, and improving the overall stability and power supply reliability of the power system. It is of great significance to the safe and stable operation of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the process of the present invention; Figure 2 This is a flow chart of the present invention for determining a fault phase; Figure 3 This is a wiring diagram of a dry-type transformer interlayer insulation fault test according to an embodiment of the present invention; Figure 4 Schematic diagram of a dry-type transformer simulation analysis model constructed hierarchically based on ANSYS finite element simulation software in an embodiment of the present invention; Figure 5 It is a side view of the dry-type transformer simulation analysis model; Figure 6 It is a top view of the dry-type transformer simulation analysis model; Figure 7 It is a structural diagram of the information collection system in an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The embodiments of the present invention are further described below with reference to the accompanying drawings: like Figure 1 As shown, a method for detecting the interlayer insulation state of a dry-type transformer includes the following steps: S1. For the dry-type transformer being tested, a layered dry-type transformer simulation analysis model is constructed in the finite element simulation software; S2. Based on the current and voltage transformers and three-phase voltage regulator installed on the dry-type transformer, determine the resistance value of the critical state of interlayer insulation degradation and critical state of collapse of the dry-type transformer through interlayer insulation fault test; S3. Based on the dry-type transformer simulation analysis model, simulate and obtain the sensitive state value of the dry-type transformer interlayer insulation degradation critical state , and the sensitive state value of dry-type transformer interlayer insulation collapse critical state ; S4. Collect the voltage and current of the three-phase high-voltage and low-voltage windings of the dry-type transformer under actual working conditions, and calculate the actual sensitive state value of each phase during the operation of the dry-type transformer ,and and Compare and determine the insulation status between each phase of the dry-type transformer being tested.

[0020] In S1, the "electromagnetic field-external circuit" coupling in the ANSYS finite element simulation software was used to build a three-dimensional model consistent with the actual transformer, and each phase winding on the high-voltage side of the three-dimensional model was layered according to the actual situation to obtain a dry-type transformer simulation analysis model.

[0021] In S2, the method for determining the resistance value of the critical state of interlayer insulation degradation and critical state of collapse of dry-type transformers through interlayer insulation fault test is as follows: S2.1. Connect the three-phase winding on the high-voltage side of a dry-type transformer to a three-phase voltage regulator. Leave the low-voltage winding open. Connect the taps connecting two adjacent layers of the high-voltage winding of the dry-type transformer via contact resistors to simulate the interlayer insulation resistance under different degrees of insulation degradation. Use current and voltage transformers to monitor the current flowing through the contact resistors and the voltage across them. S2.2. Gradually increase the voltage of the high-voltage winding using a three-phase voltage regulator. Within the maximum current range that the high-voltage winding conductor can withstand, measure the current flowing through the short-circuited turn until the maximum current that the conductor can withstand is reached and then stop increasing the voltage. S2.3. Based on the measured interlayer insulation resistance-fault layer current relationship curve, take the two interlayer insulation resistance values corresponding to the two points with the largest rate of change on the curve as the resistance values of the critical state of interlayer insulation degradation and the critical state of collapse. The larger resistance value is the resistance value of the critical state of interlayer insulation degradation, and the smaller resistance value is the resistance value of the critical state of interlayer insulation collapse.

[0022] The relationship between the insulation resistance between winding layers and the fault layer current is expressed as: ; Where, is the winding fault layer current; is the induced voltage of the winding fault layer; is the winding fault layer resistance; is the interlayer insulation resistance.

[0023] In S3, based on the resistance values of the critical state of interlayer insulation degradation and the critical state of collapse of the dry-type transformer obtained in S2, the interlayer insulation resistance value of a phase winding is set in the external circuit of the dry-type transformer simulation analysis model, and the critical state of interlayer insulation degradation and the critical state of collapse of the phase are simulated accordingly. The sensitive state quantity values of the critical state of interlayer insulation degradation and the critical state of collapse of the dry-type transformer are determined according to the voltage and current mutation conditions. 、 , and verify 、 The error between the corresponding sensitive state quantity value measured in the interlayer insulation fault test is within the allowable range.

[0024] In S4, The calculation method is as follows: take the zero-sequence component into account to measure the unbalance, use the difference between the improved voltage and current unbalance as the sensitive state quantity, and standardize the sensitive state quantity into per-unit value: Improve voltage imbalance : ; Improved current imbalance : ; Actual value of sensitive state quantity : ; Will Per-unit value: ; Where, 、 、 Represent the positive sequence, negative sequence and zero sequence voltage components on the high voltage side of the dry-type transformer respectively; 、 、 Represent the positive sequence, negative sequence and zero sequence current components of the high voltage side of the dry-type transformer respectively; 、 、 They represent the normalized positive-sequence, negative-sequence and zero-sequence voltage components on the high-voltage side of the dry-type transformer respectively; 、 、 They represent the normalized positive-sequence, negative-sequence and zero-sequence current components on the high-voltage side of the dry-type transformer respectively.

[0025] The method for determining the insulation status of each phase of the dry-type transformer being tested is as follows: When the insulation between layers is normal; when When , the interlayer insulation is in the damage warning state; when When , the interlayer insulation is in a breakdown state.

[0026] When the interlayer insulation is in a damage warning state, an early warning command is issued and a visual output is performed; when the interlayer insulation is in a collapse state, a tripping command is issued and a visual output is performed.

[0027] The complete fault phase judgment process is as follows: Figure 2 As shown, after the trip command is issued, the phase where the fault occurs is determined based on the sensitive state quantity value of each phase. For example, if the sensitive state quantity value of phase A is the largest, it is determined that phase A has a fault.

[0028] In S5, the voltage and current of the three-phase high-voltage and low-voltage windings of the dry-type transformer under actual working conditions are collected through the information collection system. The information collection system includes a low-voltage winding voltage / current sensor, a high-voltage winding voltage / current sensor, a signal collection unit, a logic analysis unit, a communication unit and a human-machine interface. The low-voltage winding voltage / current sensor and the high-voltage winding voltage / current sensor are respectively installed in the low-voltage winding and high-voltage winding of the dry-type transformer. The output end of each voltage / current sensor is connected to the signal input end of the signal collection unit, the output end of the signal collection unit is connected to the input end of the logic analysis unit, and the output end of the logic analysis module is connected to the human-machine interface through the communication unit.

[0029] Figure 3 This is an exemplary wiring diagram for a dry-type transformer interlayer insulation fault test. Figure 3 Middle: C TA 、C TB 、C TC Current transformer for high voltage winding; C Td High voltage current transformer for short circuit layer; L A , L B , L C , L a , L b , L c and L A1 , L A2 is the inductance of the high and low voltage windings and the non-short-circuit layer of the short-circuit phase; R A 、R B 、R C 、R a 、R b 、R c and R a1 、R a2 L is the resistance of high and low voltage windings and non-short circuit layer of short circuit phase; AD 、R AD is the inductance and resistance of the short-circuit layer; R dld is the interlayer insulation resistance; U A 、U B 、U C are the phase voltages applied to the high voltage side of the dry-type transformer through the three-phase voltage regulator; I A , I B , I C , I a , I b , I c , I d The currents of high and low voltage windings and short-circuit layers are measured. During the test, the low voltage winding of the transformer is open, and the voltage of the high voltage winding is gradually increased using a three-phase voltage regulator to detect changes in the current flowing through the high voltage winding and the fault layer.

[0030] Figure 4-Figure 6 This is an exemplary schematic diagram of a dry-type transformer simulation analysis model constructed hierarchically based on ANSYS finite element simulation software.

[0031] The schematic diagram of the information collection system is as follows: Figure 7 As shown, the information acquisition system includes a current acquisition system and a voltage acquisition system. In the current acquisition system, a low-voltage winding current sensor and a high-voltage winding current sensor are installed in the low-voltage winding and high-voltage winding of the dry-type transformer, respectively. The output of the current sensor is connected to the signal input of the signal acquisition unit, which is connected to the input of the logic analysis unit. The output of the logic analysis module is connected to the human-machine interface via a communication unit. In the voltage acquisition system, a low-voltage winding voltage sensor, a high-voltage winding voltage sensor, a signal acquisition unit, a logic analysis unit, a communication unit, and a human-machine interface are installed in the low-voltage winding and high-voltage winding of the dry-type transformer, respectively. The output of the voltage sensor is connected to the signal input of the signal acquisition unit, which is connected to the input of the logic analysis unit. The output of the logic analysis module is connected to the human-machine interface via the communication unit.

[0032] The current acquisition system and the voltage acquisition system can share the signal acquisition unit, logic analysis unit, communication unit and human-machine interface.

[0033] Example 2: A device for detecting the interlayer insulation status of a dry-type transformer includes a memory, a processor, and a computer program stored in the memory and capable of running on the processor. The method in Example 1 is implemented by executing the computer program by the processor.

Claims

1. A method for detecting the insulation state between layers of a dry-type transformer, characterized in that The following steps are involved: S1. For the dry-type transformer being tested, a layered dry-type transformer simulation analysis model is constructed in the finite element simulation software; S2. Based on the current and voltage transformers and three-phase voltage regulator installed on the dry-type transformer, determine the resistance value of the critical state of interlayer insulation degradation and critical state of collapse of the dry-type transformer through interlayer insulation fault test; S3. Based on the dry-type transformer simulation analysis model, simulate and obtain the sensitive state value of the dry-type transformer interlayer insulation degradation critical state , and the sensitive state quantity value of dry-type transformer interlayer insulation collapse critical state ; S4. Collect the voltage and current of the three-phase high-voltage and low-voltage windings of the dry-type transformer under actual working conditions, and calculate the actual sensitive state value of each phase during the operation of the dry-type transformer ,and and Compare and determine the insulation status between each phase of the dry-type transformer being tested.

2. The method for detecting the interlayer insulation state of a dry-type transformer according to claim 1, characterized in that: In the above S1, the "electromagnetic field-external circuit" coupling in the ANSYS finite element simulation software is used to build a three-dimensional model consistent with the actual transformer, and each phase winding on the high-voltage side of the three-dimensional model is layered according to the actual situation to obtain a dry-type transformer simulation analysis model.

3. The method for detecting the interlayer insulation state of a dry-type transformer according to claim 1, characterized in that: In the above S2, the method for determining the resistance value of the critical state of degradation and the critical state of collapse of the interlayer insulation of the dry-type transformer through the interlayer insulation failure test is as follows: S2.

1. Connect the three-phase winding on the high-voltage side of a dry-type transformer to a three-phase voltage regulator. Leave the low-voltage winding open. Connect the taps connecting two adjacent layers of the high-voltage winding of the dry-type transformer via contact resistors to simulate the interlayer insulation resistance under different degrees of insulation degradation. Use current and voltage transformers to monitor the current flowing through the contact resistors and the voltage across them. S2.

2. Gradually increase the voltage of the high-voltage winding using a three-phase voltage regulator. Within the maximum current range that the high-voltage winding conductor can withstand, measure the current flowing through the short-circuited turn until the maximum current that the conductor can withstand is reached and then stop increasing the voltage. S2.

3. Based on the measured interlayer insulation resistance-fault layer current relationship curve, take the two interlayer insulation resistance values corresponding to the two points with the largest rate of change on the curve as the resistance values of the critical state of interlayer insulation degradation and the critical state of collapse. The larger resistance value is the resistance value of the critical state of interlayer insulation degradation, and the smaller resistance value is the resistance value of the critical state of interlayer insulation collapse.

4. The method for detecting the interlayer insulation state of a dry-type transformer according to claim 3, characterized in that: The relationship between the insulation resistance between winding layers and the fault layer current is expressed as: ； Where, is the winding fault layer current; is the induced voltage of the winding fault layer; is the winding fault layer resistance; is the interlayer insulation resistance.

5. The method for detecting the interlayer insulation state of a dry-type transformer according to claim 2, characterized in that: In the above S3, based on the resistance value of the critical state of interlayer insulation degradation and the critical state of collapse of the dry-type transformer obtained in S2, the interlayer insulation resistance value of a certain phase winding is set in the external circuit of the dry-type transformer simulation analysis model, and the critical state of interlayer insulation degradation and the critical state of collapse of the phase are simulated accordingly. The sensitive state quantity value of the critical state of interlayer insulation degradation and the critical state of collapse of the dry-type transformer is determined according to the voltage and current mutation conditions. 、 , and verify 、 The error between the corresponding sensitive state quantity value measured in the interlayer insulation fault test is within the allowable range.

6. The method for detecting the interlayer insulation state of a dry-type transformer according to claim 1, characterized in that: In the S4, The calculation method is as follows: take the zero-sequence component into account to measure the unbalance, use the difference between the improved voltage and current unbalance as the sensitive state quantity, and standardize the sensitive state quantity into per-unit value: Improve voltage imbalance : ； Improved current imbalance : ； Actual value of sensitive state quantity : ； Will Per-unit value: ； Where, 、 、 Represent the positive sequence, negative sequence and zero sequence voltage components on the high voltage side of the dry-type transformer respectively; 、 、 Represent the positive sequence, negative sequence and zero sequence current components of the high voltage side of the dry-type transformer respectively; 、 、 They represent the normalized positive-sequence, negative-sequence and zero-sequence voltage components on the high-voltage side of the dry-type transformer respectively; 、 、 They represent the normalized positive-sequence, negative-sequence and zero-sequence current components on the high-voltage side of the dry-type transformer respectively.

7. The method for detecting the interlayer insulation state of a dry-type transformer according to claim 1, characterized in that: In the above S4, the method for determining the insulation state of each phase of the dry-type transformer being tested is as follows: When the insulation between layers is normal; when When , the interlayer insulation is in the damage warning state; when When , the interlayer insulation is in a breakdown state.

8. The method for detecting the interlayer insulation state of a dry-type transformer according to claim 7, characterized in that: When the interlayer insulation is in a damage warning state, an early warning command is issued and a visual output is performed; when the interlayer insulation is in a collapse state, a tripping command is issued and a visual output is performed.

9. The method for detecting the interlayer insulation status of a dry-type transformer according to claim 1, characterized in that: In the S5, the voltage and current of the three-phase high-voltage and low-voltage windings of the dry-type transformer under actual working conditions are collected through the information acquisition system. The information acquisition system includes a low-voltage winding voltage / current sensor, a high-voltage winding voltage / current sensor, a signal acquisition unit, a logic analysis unit, a communication unit and a human-machine interface. The low-voltage winding voltage / current sensor and the high-voltage winding voltage / current sensor are respectively installed in the low-voltage winding and high-voltage winding of the dry-type transformer. The output end of each voltage / current sensor is connected to the signal input end of the signal acquisition unit, the output end of the signal acquisition unit is connected to the input end of the logic analysis unit, and the output end of the logic analysis module is connected to the human-machine interface through the communication unit.

10. A device for detecting the interlayer insulation state of a dry-type transformer, characterized in that: The method comprises a memory, a processor, and a computer program stored in the memory and capable of running on the processor, wherein the method according to any one of claims 1 to 9 is implemented by executing the computer program by the processor.

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