Method and device for locating fault of grounding point inside transformer core and clamp

Abstract

The present invention provides a method and device for locating the fault of the internal grounding point of the transformer core and the clamp, which belongs to the field of transformer fault diagnosis; the method includes determining the type of internal grounding defects of the transformer core and the clamp; selecting the excitation type according to the defect type to test the fault point; and determining the position of the fault point according to the test result of the fault point. The positioning device includes an output terminal, an excitation unit, a detection unit, a signal processing unit and a protection unit; the protection unit is connected in series between the output terminal and the excitation unit, the output terminal is connected to the transformer core or the clamp lead wire through a wire, the detection unit is connected to the signal processing unit through a coaxial cable, and the detection unit is used to monitor the acoustic pulse signal of the transformer housing, and detect the electrical pulse signal flowing through the core or the clamp lead wire. The present invention can locate the fault point of the core and the clamp, thereby quickly repairing the core and the clamp and reducing the fault time.

Description

Technical Field

[0001] The invention relates to the technical field of transformer fault monitoring, and in particular to a method and device for locating faults of grounding points inside a transformer core and a clamp. Background Art

[0002] In recent years, as the service life of transformers increases, transformer core and clamp insulation defects such as low insulation or abnormal grounding current defects have become more frequent, posing potential risks to the safe and stable operation of DC projects. According to incomplete statistics, a total of 14 transformers in operation had low core and clamp insulation or abnormal grounding current defects from 2015 to 2019, with 5, 2, 2, 2, and 4 occurring in 2015, 2016, 2017, 2018, and 2019, respectively (including 1 unhandled case in 2018). Among them, there were 2 failures of low core insulation to ground, accounting for 14.3%, 10 failures of low core and clamp insulation, accounting for 71.4%, and 2 failures of low clamp insulation to ground or abnormal increase in ground current, accounting for 14.3%.

[0003] The insulation structure of the core and clamps is complex, and the insulation level is 2500V DC and 3.0kV AC. The search range of multi-point grounding of the core and clamps is huge, and even in the case of oil drainage and internal inspection, most positions are difficult to observe manually. The abnormality of the transformer core and clamps is crucial to the stable operation of the converter substation. By monitoring the core and clamps of the transformer, the specific fault type of the transformer can be obtained. However, the existing fault monitoring of the core and clamps can only detect faults, and the specific fault location cannot be accurately obtained, which causes great difficulties for subsequent repair and maintenance.

[0004] Therefore, there is an urgent need for a method that can monitor and locate the fault points of the internal grounding points of the transformer core and the clamps to achieve rapid fault point location. Summary of the invention

[0005] In order to solve the above-mentioned deficiencies of the prior art, the present invention provides a method and device for locating the fault of the grounding point inside the transformer core and the clamp, which can locate the fault point of the grounding point inside the core and the clamp, thereby quickly realizing the maintenance of the core and the clamp and reducing the fault time.

[0006] The purpose of the present invention can be achieved by adopting the following technical solutions:

[0007] The present invention provides a method for locating a grounding point fault inside a transformer core and a clamp, comprising:

[0008] Determine the type of internal grounding defects in the transformer core and clamps;

[0009] Select the stimulus type according to the defect type to perform fault point testing;

[0010] Determine the location of the fault point based on the test results of the fault point.

[0011] As a further technical solution of the present invention, the method of determining the internal grounding defect type of the transformer core and the clamp specifically includes:

[0012] In the insulation resistance test function mode, use 9V DC voltage to detect the transformer's iron core-to-ground insulation resistance, the clamp-to-ground insulation resistance, and the iron core-to-clamp insulation resistance. When the resistance value of one of the insulation resistances is <10kΩ, it is a low-resistance grounding defect; when the resistance value of one of the insulation resistances is between 10kΩ and 0.1MΩ, it is a high-resistance grounding defect.

[0013] As a further technical solution of the present invention, the excitation type is selected according to the defect type to perform fault point testing; specifically, it includes: actively exciting the transformer core and clamps; the types of active excitation include DC voltage excitation and AC voltage excitation; wherein, the DC voltage excitation is a voltage peak value not exceeding 200V after being released through capacitor energy storage; and the AC voltage excitation is a voltage peak value not exceeding 400V after being regulated by an industrial frequency voltage regulator.

[0014] As a further technical solution of the present invention, the position of the fault point is determined according to the test result of the fault point; specifically comprising:

[0015] Arrange an acoustic pulse sensor on the transformer housing, and connect an electric pulse sensor in series to the output terminal excitation input wire;

[0016] When it is a low-resistance grounding defect, open the connection between the clamp down conductor and the box shell;

[0017] Select the DC voltage excitation function mode;

[0018] The protection unit selects the DC excitation selection switch;

[0019] Output excitation and collect pulse signals through the detection unit, and send them to the signal processing unit after conditioning;

[0020] The signal processing unit uses the acoustic pulse signal and the electrical pulse signal to complete the calculation of the position of the grounding defect point according to the positioning method.

[0021] As a further technical solution of the present invention, the signal processing unit uses the acoustic pulse signal and the electrical pulse signal to complete the calculation of the position of the grounding defect point according to the positioning method, which specifically includes:

[0022] Calculate the time difference between each acoustic pulse signal and the electrical pulse signal;

[0023] The time difference is converted into the distance difference of the sound pulse by using the speed of sound in the insulating oil;

[0024] Make a tetrahedron with three sensors as vertices and the distance difference of the acoustic pulses of each sensor as the edge;

[0025] The intersection of two or more tetrahedrons is taken as the positioning result.

[0026] As a further technical solution of the present invention, the position of the fault point is determined according to the test result of the fault point; specifically comprising:

[0027] Arrange an acoustic pulse sensor on the transformer housing, and connect an electric pulse sensor in series to the output terminal excitation input wire;

[0028] When it is a high-resistance grounding defect, open the connection between the clamp down conductor and the box shell;

[0029] Select the power frequency voltage regulation excitation function mode;

[0030] The protection unit selects the power frequency excitation selection switch, and the protection resistor selects 2kΩ;

[0031] Slowly increase the power frequency voltage output, and simultaneously observe whether the detection unit has collected an obvious continuous pulse signal. When the pulse signal continues to appear, stop changing the power frequency voltage.

[0032] The detection unit collects the pulse signal and sends it to the signal processing unit after conditioning;

[0033] The signal processing unit uses the acoustic pulse signal and the electrical pulse signal to complete the calculation of the position of the grounding defect point according to the positioning method.

[0034] As a further technical solution of the present invention, the signal processing unit uses the acoustic pulse signal and the electrical pulse signal to complete the calculation of the position of the grounding defect point according to the positioning method, which specifically includes:

[0035] Calculate the time difference between each acoustic pulse signal and the electrical pulse signal;

[0036] The time difference is converted into the distance difference of the sound pulse by using the speed of sound in the insulating oil;

[0037] Make a tetrahedron with three sensors as vertices and the distance difference of the acoustic pulses of each sensor as the edge;

[0038] The intersection of two or more tetrahedrons is taken as the positioning result.

[0039] The present invention also provides a device for locating a grounding point fault inside a transformer core and a clamp, comprising: an output terminal, an excitation unit, a detection unit, a signal processing unit and a protection unit; the protection unit is connected in series between the output terminal and the excitation unit, the output terminal is connected to the transformer core or the clamp lead wire through a wire, the detection unit is connected to the signal processing unit through a coaxial cable, and the detection unit is used to monitor the acoustic pulse signal of the transformer casing and detect the electrical pulse signal flowing through the core or the clamp lead wire.

[0040] As a further technical solution of the present invention, the excitation unit includes:

[0041] Power frequency voltage regulation excitation, including current measurement module, power frequency voltage regulation module, voltage measurement module;

[0042] DC voltage excitation, including a DC power supply, an energy storage capacitor and a voltage measurement module;

[0043] DC excitation, including a DC power supply, a current measurement module and a voltage measurement module.

[0044] As a further technical solution of the present invention, the protection unit includes: a power frequency voltage regulation excitation selection switch, a DC excitation selection switch, an insulation resistance selection switch and a protection resistor;

[0045] The output terminals include an excitation input terminal, an excitation output terminal and a ground output terminal.

[0046] The detection unit includes: an acoustic pulse sensor, an electric pulse sensor, a multi-channel acoustic pulse input module, a single-channel electric pulse input module and a signal conditioning module. The output end of the acoustic pulse sensor is connected to the multi-channel acoustic pulse input module, the output end of the electric pulse sensor is connected to the single-channel electric pulse input module, and the output ends of the multi-channel acoustic pulse input module and the single-channel electric pulse input module are connected to the signal conditioning module.

[0047] The present invention has the following beneficial effects compared with the prior art:

[0048] 1. The present invention monitors the insulation anomalies of the iron core and the clamps of the converter substation. First, the fault type of the iron core and the clamps is determined, including low-resistance grounding defects and high-resistance grounding defects; the fault point test is performed according to the fault type of the transformer iron core and the clamps; and the fault point location is determined according to the test results of the fault point.

[0049] 2. Test the insulation resistance of the core and the clamps according to different voltage levels. When the insulation resistance is the corresponding voltage level resistance, it is judged as a low-resistance grounding defect. When the insulation resistance is less than 30% of the corresponding voltage level resistance, it is judged as a high-resistance grounding defect. After the fault type is judged, different test methods are used according to different fault types.

[0050] 3. The present invention searches for ultrasonic pulse partial discharge signals with higher amplitudes based on the measured ultrasonic signals and the recorded amplitudes, and calculates the time difference between the ultrasonic pulse signal of the ultrasonic probe and the high-frequency pulse signal of the loop. When the time difference between the ultrasonic pulse signal of the ultrasonic probe and the high-frequency pulse signal of the loop is zero or close to zero, it can be determined that the grounding point of the iron core and the clamp is near the ultrasonic probe. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0052] Figure 1 This is a flow chart of the method for locating the fault of the transformer core and the internal grounding point of the clamp proposed by the present invention;

[0053] Figure 2 A schematic diagram of a specific embodiment of the present invention;

[0054] Figure 3 This is a test result diagram of the fourth monitoring proposed by the present invention;

[0055] Figure 4 This is a test result diagram of the cover plate 6 proposed by the present invention;

[0056] Figure 5 This is a structural diagram of the transformer core and the internal grounding point fault location device proposed by the present invention;

[0057] Figure 6 The control structure diagram of the excitation unit proposed by the present invention;

[0058] Figure 7 This is a control structure diagram of the wiring terminal proposed by the present invention;

[0059] Figure 8 This is a control structure diagram of the protection unit proposed by the present invention;

[0060] Fig. 9 This is a control structure diagram of the detection unit proposed in the present invention. DETAILED DESCRIPTION

[0061] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. It should be understood that the specific embodiments described are only used to explain the present application and are not used to limit the present application.

[0062] See also Figure 1 The present invention provides a method for locating a grounding point fault inside a transformer core and a clamp, comprising:

[0063] Step 101, determining the internal grounding defect type of the transformer core and the clamp;

[0064] Step 102, selecting an excitation type according to the defect type to perform a fault point test;

[0065] Step 103: determine the location of the fault point according to the test result of the fault point.

[0066] In an embodiment of the present invention, insulation anomalies of the core and clamps of a converter substation are monitored. First, the fault type of the core and clamps is determined, including low-resistance grounding defects and high-resistance grounding defects; the fault point test is performed according to the fault type of the transformer core and clamps; and the fault point location is determined according to the test result of the fault point.

[0067] In step 101, determining the internal grounding defect type of the transformer core and the clamp specifically includes:

[0068] In the insulation resistance test function mode, use 9V DC voltage to test the insulation resistance of the transformer's iron core to ground (tank shell), the insulation resistance of the clamp to ground (tank shell), and the insulation resistance of the iron core and the clamp. When the resistance value of one of the insulation resistances is <10kΩ, it is a low-resistance grounding defect; when the resistance value of one of the insulation resistances is between 10kΩ and 0.1MΩ, it is a high-resistance grounding defect.

[0069] In step 102, the excitation type is selected according to the defect type to perform fault point testing; specifically, it includes: actively exciting the transformer core and clamps; the types of active excitation include DC voltage excitation and AC voltage excitation; wherein, the DC voltage excitation is a voltage peak value not exceeding 200V after the capacitor energy storage is released; the AC voltage excitation is a voltage peak value not exceeding 400V after being regulated by the power frequency voltage regulator.

[0070] When it is a low-resistance grounding defect, use DC voltage excitation to test the fault point;

[0071] When it is a high-resistance grounding defect, AC voltage excitation is used to perform fault point testing.

[0072] The insulation resistance of the core and the clamps is tested according to different voltage levels. After the fault type is determined, different testing methods are used according to different fault types.

[0073] When it is a low-resistance grounding defect, open the clamp lead to connect to the ground; ground the oscilloscope and signal generator; use a multimeter to test the DC resistance of the clamp to the ground (box shell), and record and keep; connect the audio antenna to the oscilloscope; set the signal generator to sweep mode; connect one end of the coaxial cable at the output port of the signal generator to the box shell; connect the core wire of the signal generator to the clamp lead; use the audio antenna to test the signal amplitude at the clamp lead to ensure that the test circuit is normal; use the audio antenna to detect the sweep signal at each cover plate, and record the amplitude of each cover plate. Among them, the sweep range of the signal generator is 10kHz to 500kHz.

[0074] For low-resistance grounding defects, a signal generator, an audio antenna, an oscilloscope and a portable partial discharge meter are used to test the suspected fault points of the low-resistance grounding defects. The signal generator is used to ensure that the test circuit is normal. The swept frequency signal is detected by the audio antenna to obtain the signal amplitude of each cover plate.

[0075] When it is a high-resistance grounding defect, the fault point test is carried out using power frequency voltage regulation excitation, which specifically includes: setting multiple ultrasonic sensors on the transformer box; opening the clamp lead to connect to the ground; grounding the power frequency voltage regulator and the portable partial discharge instrument; using a pulse source to calibrate the correctness of the portable partial discharge instrument test; using a multimeter to test the DC resistance of the clamp to the ground (box shell) and record it; connecting the front end of the power frequency voltage regulator to the clamp lead and the rear end to the transformer box shell; connecting the ultrasonic sensor to the portable partial discharge instrument; putting the high-frequency current sensor on the tail lead of the voltage regulator and connecting it to the portable partial discharge instrument; adjusting the voltage regulator to output different partial discharge amounts to collect the ultrasonic partial discharge signal of the pressure nail cover on the top of the transformer.

[0076] For high-resistance grounding defects, a single-phase power frequency voltage regulator, an ultrasonic probe, an oscilloscope, a high-frequency current sensor and a portable partial discharge meter are used to test the suspected fault points. The power frequency voltage regulator is used to output the time difference of the received signals obtained by the ultrasonic probe.

[0077] In the embodiment of the present invention, adjusting the voltage regulator to output different partial discharge amounts to collect ultrasonic partial discharge signals of the pressure nail cover plate on the top of the transformer specifically includes:

[0078] Adjust the output voltage of the voltage regulator until 500pC partial discharge occurs; use an ultrasonic sensor to measure the ultrasonic signal of each cover plate and record the amplitude;

[0079] Adjust the output voltage of the voltage regulator until 700pC partial discharge occurs; use an ultrasonic sensor to measure the ultrasonic signal of each cover plate and record the amplitude;

[0080] The output voltage of the voltage regulator was adjusted until a partial discharge of 1000 pC occurred; an ultrasonic sensor was used to measure the ultrasonic signal of each cover plate and the amplitude was recorded.

[0081] In step 103, the location of the fault point is determined according to the test result of the fault point; specifically, the method includes:

[0082] Arrange an acoustic pulse sensor on the transformer housing, and connect an electric pulse sensor in series to the output terminal excitation input wire;

[0083] When it is a low-resistance grounding defect, open the connection between the clamp down conductor and the box shell;

[0084] Select the DC voltage excitation function mode;

[0085] The protection unit selects the DC excitation selection switch;

[0086] Output excitation and collect pulse signals through the detection unit, and send them to the signal processing unit after conditioning;

[0087] The signal processing unit uses the acoustic pulse signal and the electrical pulse signal to complete the calculation of the position of the grounding defect point according to the positioning method.

[0088] In the embodiment of the present invention, the signal processing unit uses the acoustic pulse signal and the electrical pulse signal to complete the calculation of the position of the ground defect point according to the positioning method, which specifically includes:

[0089] Calculate the time difference between each acoustic pulse signal and the electrical pulse signal;

[0090] The time difference is converted into the distance difference of the sound pulse by using the speed of sound in the insulating oil;

[0091] Make a tetrahedron with three sensors as vertices and the distance difference of the acoustic pulses of each sensor as the edge;

[0092] The intersection of two or more tetrahedrons is taken as the positioning result.

[0093] In step 103, the location of the fault point is determined according to the test result of the fault point; specifically, the method includes:

[0094] Arrange an acoustic pulse sensor on the transformer housing, and connect an electric pulse sensor in series to the output terminal excitation input wire;

[0095] When it is a high-resistance grounding defect, open the connection between the clamp down conductor and the box shell;

[0096] Select the power frequency voltage regulation excitation function mode;

[0097] The protection unit selects the power frequency excitation selection switch, and the protection resistor selects 2kΩ;

[0098] Slowly increase the power frequency voltage output, and simultaneously observe whether the detection unit has collected an obvious continuous pulse signal. When the pulse signal continues to appear, stop changing the power frequency voltage.

[0099] The detection unit collects the pulse signal and sends it to the signal processing unit after conditioning;

[0100] The signal processing unit uses the acoustic pulse signal and the electrical pulse signal to complete the calculation of the position of the grounding defect point according to the positioning method.

[0101] In the embodiment of the present invention, the signal processing unit uses the acoustic pulse signal and the electrical pulse signal to complete the calculation of the position of the ground defect point according to the positioning method, which specifically includes:

[0102] Calculate the time difference between each acoustic pulse signal and the electrical pulse signal;

[0103] The time difference is converted into the distance difference of the sound pulse by using the speed of sound in the insulating oil;

[0104] Make a tetrahedron with three sensors as vertices and the distance difference of the acoustic pulses of each sensor as the edge;

[0105] The intersection of two or more tetrahedrons is taken as the positioning result.

[0106] The present invention searches for ultrasonic pulse partial discharge signals with higher amplitudes according to the measured ultrasonic signals and the recorded amplitudes, and simultaneously calculates the time difference between the ultrasonic pulse signals of the ultrasonic probe and the high-frequency pulse signals of the loop. When the time difference between the ultrasonic pulse signals of the ultrasonic probe and the high-frequency pulse signals of the loop is zero or close to zero, it can be determined that the grounding points of the iron core and the clamp are near the ultrasonic probe.

[0107] As a further technical solution of the present invention, it includes: an output terminal, an excitation unit, a detection unit, a signal processing unit and a protection unit; the protection unit is connected in series between the output terminal and the excitation unit, the output terminal is connected to the transformer core or the clamp lead wire through a wire, the detection unit is connected to the signal processing unit through a coaxial cable, and the detection unit is used to monitor the acoustic pulse signal of the transformer casing and detect the electrical pulse signal flowing through the core or the clamp lead wire.

[0108] As a further technical solution of the present invention, the excitation unit includes:

[0109] Power frequency voltage regulation excitation, including current measurement module, power frequency voltage regulation module, voltage measurement module;

[0110] DC voltage excitation, including a DC power supply, an energy storage capacitor and a voltage measurement module;

[0111] DC excitation, including a DC power supply, a current measurement module and a voltage measurement module.

[0112] As a further technical solution of the present invention, the protection unit includes: a power frequency voltage regulation excitation selection switch, a DC excitation selection switch, an insulation resistance selection switch and a protection resistor;

[0113] The output terminals include an excitation input terminal, an excitation output terminal and a ground output terminal.

[0114] The detection unit includes: an acoustic pulse sensor, an electric pulse sensor, a multi-channel acoustic pulse input module, a single-channel electric pulse input module and a signal conditioning module. The output end of the acoustic pulse sensor is connected to the multi-channel acoustic pulse input module, the output end of the electric pulse sensor is connected to the single-channel electric pulse input module, and the output ends of the multi-channel acoustic pulse input module and the single-channel electric pulse input module are connected to the signal conditioning module.

[0115] The data processing unit of the present invention performs time difference calculation based on the acoustic pulse signal and the electrical pulse signal obtained by the detection unit, converts the time difference signal into distance using the sound speed in the insulating oil, uses the coordinates of three sensors as the vertices of the tetrahedron, and uses the distance as the side length of the tetrahedron to obtain a tetrahedron. The intersection of more than two tetrahedrons is the defect point positioning result.

[0116] See also Figure 2 , which is a schematic diagram of a specific embodiment provided by the present invention; in the embodiment of the present invention, during the positioning process, a power frequency voltage regulator is used to apply a power frequency excitation of no more than 200V between the clamp and the box shell, monitor the high-frequency partial discharge signal of the test circuit, and collect the ultrasonic partial discharge signal of the pressure nail cover plate on the top of the converter transformer. Considering that there are 20 pressure nail covers on the top of the converter transformer and there are 6 acoustic pulse signal channels of the positioning device, "partition monitoring, gradually narrowing the scope, and centralized comparison" are used;

[0117] During the positioning process, the insulation resistance test function was used, and the insulation resistance of the clamp to the box shell was measured to be 2.4 ohms;

[0118] Select the power frequency excitation function to improve the power frequency excitation output, and collect stable acoustic pulse signals and electrical pulse signals when the output voltage is 170V;

[0119] Three positioning tests were completed in three areas, and the test results are shown in the table;

[0120]

[0121] For the fourth test target, the results of the first three tests were sorted from small to large according to the time difference, and combined with the sensor position relationship, it was finally found that the four pressure nail cover plates located near the center of the device body had obvious ultrasonic pulse partial discharge signals.

[0122] See also Figure 3 , which is the fourth test structure diagram; the cover number of the fourth monitoring is 6 / 7 / 16 / 17, and the test results are as follows Figure 3 , the upper pulse in the figure is an electric pulse signal, and the four lower ones are acoustic pulse signals of 6 / 7 / 16 / 17. During the four positioning processes, the lowest discharge voltage was 129V (around 13:00 noon), and the circuit discharge current was 3.98mA; the highest discharge voltage was 195V (around 3:00 am), and the circuit discharge current was 2.42mA. The positioning results show that the grounding point of the clamp is near cover plate No. 6.

[0123] See also Figure 4 The time difference between the ultrasonic pulse signal of the No. 6 pressure nail cover and the loop high-frequency pulse signal is basically zero, the spatial distance is about 3cm, and the quantity and position of the two types of pulse signals are very consistent. The ultrasonic signals on the other covers lag behind the No. 6 pressure nail cover.

[0124] See also Figure 5 The present invention also provides a device for locating a grounding point fault inside a transformer core and a clamp, comprising: an output terminal, an excitation unit, a detection unit and a protection unit; the protection unit is connected in series between the output terminal and the excitation unit, the output terminal is connected to the transformer core or the clamp lead wire through a wire, and the detection unit is used to monitor the acoustic pulse signal of the transformer casing and detect the electrical pulse signal flowing through the core or the clamp lead wire.

[0125] See also Figure 6 , the excitation unit includes:

[0126] Power frequency voltage regulation excitation, including current measurement module, power frequency voltage regulation module, voltage measurement module;

[0127] DC voltage excitation, including a DC power supply, an energy storage capacitor and a voltage measurement module;

[0128] DC excitation, including a DC power supply, a current measurement module and a voltage measurement module.

[0129] See also Figure 7 , the protection unit includes: power frequency voltage regulation excitation selection switch, DC excitation selection switch, insulation resistance selection switch and protection resistor;

[0130] See also Figure 8 The output terminals include an excitation input terminal, an excitation output terminal and a ground output terminal.

[0131] See also Fig. 9 The detection unit includes: an acoustic pulse sensor, an electric pulse sensor, a multi-channel acoustic pulse input module, a single-channel electric pulse input module and a signal conditioning module. The output end of the acoustic pulse sensor is connected to the multi-channel acoustic pulse input module, the output end of the electric pulse sensor is connected to the single-channel electric pulse input module, and the output ends of the multi-channel acoustic pulse input module and the single-channel electric pulse input module are connected to the signal conditioning module.

[0132] The various variations and specific examples of the methods in the aforementioned embodiments are also applicable to a fault monitoring and positioning device for a transformer core and a clamp in the present embodiment. Through the aforementioned detailed description of the point debugging method for the background monitoring of the substation, those skilled in the art can clearly understand the fault monitoring and positioning device for the transformer core and a clamp in the present embodiment. Therefore, for the sake of brevity of the specification, it will not be described in detail here.

[0133] The present invention is described in detail above, but the present invention is not limited to the above-mentioned embodiments. Various changes can be made within the knowledge of ordinary technicians in the field without departing from the purpose of the present invention. Many other changes and modifications can be made without departing from the concept and scope of the present invention. It should be understood that the present invention is not limited to specific embodiments, and the scope of the present invention is defined by the appended claims.

Claims

1. A method for locating faults at grounding points inside transformer cores and clamps, characterized in that: include: Determine the type of internal grounding defects in the transformer core and clamps; Select the stimulus type according to the defect type to perform fault point testing; Determine the location of the fault point based on the test results of the fault point; Determining the location of the fault point according to the test result of the fault point specifically includes: Arrange an acoustic pulse sensor on the transformer housing, and connect an electric pulse sensor in series to the output terminal excitation input wire; When it is a low-resistance grounding defect, open the connection between the clamp down conductor and the box shell; Select the DC voltage excitation function mode; The protection unit selects the DC excitation selection switch; Output excitation and collect pulse signals through the detection unit, and send them to the signal processing unit after conditioning; The signal processing unit uses the acoustic pulse signal and the electrical pulse signal to complete the calculation of the position of the ground defect point according to the positioning method; Determining the location of the fault point according to the test result of the fault point specifically includes: Arrange an acoustic pulse sensor on the transformer housing, and connect an electric pulse sensor in series to the output terminal excitation input wire; When it is a high-resistance grounding defect, open the connection between the clamp down conductor and the box shell; Select the power frequency voltage regulation excitation function mode; The protection unit selects the power frequency voltage regulation excitation selection switch, and the protection resistor selects 2kΩ; Slowly increase the power frequency voltage output, and simultaneously observe whether the detection unit has collected an obvious continuous pulse signal. When the pulse signal continues to appear, stop changing the power frequency voltage. The detection unit collects the pulse signal and sends it to the signal processing unit after conditioning; The signal processing unit uses the acoustic pulse signal and the electrical pulse signal to complete the calculation of the position of the grounding defect point according to the positioning method.

2. The method for locating the grounding point fault inside the transformer core and the clamp according to claim 1, characterized in that: The method of determining the internal grounding defect type of the transformer core and the clamps specifically includes: In the insulation resistance test function mode, use 9V DC voltage to detect the transformer's iron core-to-ground insulation resistance, the clamp-to-ground insulation resistance, and the iron core-to-clamp insulation resistance. When the resistance value of one of the insulation resistances is <10kΩ, it is a low-resistance grounding defect; when the resistance value of one of the insulation resistances is between 10kΩ and 0.1MΩ, it is a high-resistance grounding defect.

3. The method for locating the grounding point fault inside the transformer core and the clamp according to claim 1, characterized in that: The fault point test is performed by selecting an excitation type according to the defect type; specifically including: actively exciting the transformer core and clamps; the types of active excitation include DC voltage excitation and power frequency voltage regulation excitation; wherein, the DC voltage excitation is a voltage peak value not exceeding 200V after the capacitor energy storage is released; the power frequency voltage regulation excitation is a voltage peak value not exceeding 400V adjusted by the power frequency voltage regulator.

4. The method for locating the grounding point fault inside the transformer core and the clamp according to claim 1, characterized in that: The signal processing unit uses the acoustic pulse signal and the electrical pulse signal to complete the calculation of the position of the ground defect point according to the positioning method, specifically including: Calculate the time difference between each acoustic pulse signal and the electrical pulse signal; The time difference is converted into the distance difference of the sound pulse by using the speed of sound in the insulating oil; Make a tetrahedron with three sensors as vertices and the distance difference of the acoustic pulses of each sensor as the edge; The intersection of two or more tetrahedrons is taken as the positioning result.

5. A device for locating the fault of the grounding point inside the transformer core and the clamp, characterized in that: The method as described in any one of claims 1 to 4 comprises: an output terminal, an excitation unit, a detection unit, a signal processing unit and a protection unit; the protection unit is connected in series between the output terminal and the excitation unit, the output terminal is connected to the transformer core or the clamp lead wire through a wire, the detection unit is connected to the signal processing unit through a coaxial cable, and the detection unit is used to monitor the acoustic pulse signal of the transformer casing and detect the electrical pulse signal flowing through the core or the clamp lead wire.

6. The device for locating the internal grounding point fault of the transformer core and the clamp according to claim 5, characterized in that: The excitation unit comprises: Power frequency voltage regulation excitation, including current measurement module, power frequency voltage regulation module, voltage measurement module; DC voltage excitation, including a DC power supply, an energy storage capacitor and a voltage measurement module; DC excitation, including a DC power supply, a current measurement module and a voltage measurement module.

7. The device for locating the internal grounding point fault of the transformer core and the clamp according to claim 5, characterized in that: The protection unit includes: a power frequency voltage regulation excitation selection switch, a DC excitation selection switch, an insulation resistance selection switch and a protection resistor; The output terminals include an excitation input terminal, an excitation output terminal and a ground output terminal; The detection unit includes: an acoustic pulse sensor, an electric pulse sensor, a multi-channel acoustic pulse input module, a single-channel electric pulse input module and a signal conditioning module. The output end of the acoustic pulse sensor is connected to the multi-channel acoustic pulse input module, the output end of the electric pulse sensor is connected to the single-channel electric pulse input module, and the output ends of the multi-channel acoustic pulse input module and the single-channel electric pulse input module are connected to the signal conditioning module.

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