Device and method for probing grounding point of transformer core clamp

Abstract

The invention provides a device and a method for probing a grounding point of a transformer iron core clamp, which are used for converting a low-impedance grounding point of a transformer into a high-impedance grounding point by utilizing capacitor discharge large-current impact in a low-impedance grounding state of the transformer iron core clamp. For a high-impedance grounding state of a transformer iron core clamp, partial discharge at a high-impedance grounding point of a transformer is actively excited by power frequency alternating current excitation, and the spatial position of a partial discharge point, namely a grounding fault point, is determined through an acoustic-electric combined positioning method. The problems that an existing conventional detection method cannot locate the position of a multi-point grounding fault point of the transformer iron core clamp, the potential of the fault point of the iron core clamp in the low-impedance grounding state of the transformer is low, partial discharge is weak, and acoustoelectric signals are difficult to collect are solved. When fault point positioning is carried out, a transformer shell does not need to be disassembled, and ultrasonic signals can be easily monitored at the position of a transformer box shell through capacitor impact current excitation and power frequency alternating current excitation.

Description

Technical Field

[0001] The invention relates to a transformer core clamp, and in particular to a device and method for detecting a grounding point of a transformer core clamp. Background Art

[0002] Transformers are a crucial component of power systems. With the rapid development of ultra-high voltage (UHV) transmission and transformation technology in recent years, their importance has grown. If a power outage occurs due to a fault, not only will the power sector suffer significant losses, but electricity users will also suffer significant economic losses. Therefore, the safe and stable operation of transformers is essential for maintaining power supply reliability.

[0003] Multiple-point grounding of transformer core clamps is a common transformer failure, ranking third among all transformer accidents, according to statistics. If no appropriate measures are taken, multiple-point grounding faults can not only cause the decomposition of gases in the transformer oil, causing the transformer to trip, but the thermal effects of the prolonged high current can also cause localized overheating of the core, potentially burning it.

[0004] Common methods for detecting multiple-point grounding in transformer core clamps include gas chromatography, infrared analysis, insulation resistance analysis, and ground current analysis. Gas chromatography identifies grounding problems by measuring changes in the levels of various hydrocarbons in the transformer oil. However, if the multiple-point grounding fault is not severe, the hydrocarbon content often does not change significantly. This method also has a lag, requiring the hydrocarbon content to reach a certain threshold before determining whether a fault has occurred. Infrared analysis uses infrared data acquisition equipment to measure the temperature of various transformer components to determine if a fault has occurred. However, due to the obstruction of the transformer casing and the cooling effect of the transformer oil, this method has certain limitations and is often more commonly used in dry-type transformers. The insulation resistance and ground current methods determine whether a multiple-point grounding fault has occurred by measuring the insulation resistance of the core clamp to ground and the current in the core clamp lead wires. If the insulation resistance value is too low or the lead wire current is too high, it indicates that the transformer may have a multiple-point grounding fault. The above method can often only determine whether multiple-point grounding occurs, but cannot determine the location of multiple-point grounding. During the later maintenance of the transformer cover, it is often necessary to rely on manpower to check the easily grounded areas one by one, which undoubtedly increases the difficulty of maintenance and lengthens the maintenance work cycle. Summary of the Invention

[0005] 1. Technical problems to be solved: The commonly used detection method for multi-point grounding of transformer core clamps can only determine whether multi-point grounding occurs, but cannot determine the location where the multi-point grounding occurs.

[0006] 2. Technical solution: In order to solve the above problems, the present invention provides a transformer core clamp grounding point detection device, including a voltage regulator, the input end of the voltage regulator is connected to the mains, and the output end is connected to the input end of a first double-pole triple-throw switch. When the knob is set to gear 0, its input and output ends are disconnected. When the knob is set to gear 1, the voltage regulator outputs an industrial frequency AC excitation with the same amplitude as the first double-pole triple-throw switch through the switch. When the first double-pole triple-throw switch is set to gear 2, the voltage regulator is connected to the rectifier through the switch, and the rectifier is connected to the charging capacitor. The positive and negative ends of the charging capacitor are connected in parallel with the second double-pole triple-throw switch. When The second double-pole triple-throw switch is set to gear 1, and the charging capacitor outputs an inrush current through the second double-pole triple-throw switch. The second double-pole triple-throw switch is set to gear 2, and the charging capacitor is connected to the third current-limiting resistor. The signal processor collects the ultrasonic signal and the high-frequency current pulse signal collected by the ultrasonic sensor and the high-frequency current sensor, and transmits them to the all-in-one machine after processing. The all-in-one machine receives the spatial position coordinates of the sensor input on the screen and the acoustic and electrical signals input by the signal processor, outputs the ultrasonic signal and the high-frequency current pulse signal waveform, and locates the position of the fault grounding point according to the spatial spherical formula algorithm.

[0007] Furthermore, a first current limiting resistor 501 is provided between the first double-pole triple-throw switch and the industrial frequency AC excitation output.

[0008] Furthermore, a second current limiting resistor is connected in series between the rectifier and the charging capacitor.

[0009] Furthermore, the fault grounding point of the transformer is located by combining acoustics and electricity. The specific method is as follows: a high-frequency current sensor and three ultrasonic sensors are set to detect the high-frequency current pulse signal and ultrasonic signal emitted by the partial discharge of the transformer core grounding fault point respectively. By setting three ultrasonic sensors at different positions of the transformer shell, three ultrasonic signals S1, S2, and S3 are collected, and the time difference between them and the high-frequency current pulse signal is t 1 ,t 2 ,t 3. is the propagation time of the ultrasonic signal from the fault point to the ultrasonic sensor, using the spatial spherical formula: In the formula X i， Y i， Z i are the spatial coordinates of the three ultrasonic sensors, V is the propagation speed of ultrasonic waves in transformer oil, and the two intersection points ( X a , Y a , Za ), ( X b , Y b , Z b ), where the coordinates of the intersection point inside the transformer are the spatial coordinates of the grounding fault point.

[0010] The present invention also provides a method for detecting the grounding point of a transformer core clamp, which uses the transformer core clamp grounding point detection device, including the following steps: Step 1: Turn on the power supply, change the effective value of the AC voltage through the voltage regulator, set the first double-pole triple-throw switch to gear 2, and convert the industrial frequency AC into DC through the rectifier to charge the charging capacitor.

[0011] Step 2: After the charging capacitor is fully charged, the first double-pole triple-throw switch is set to position 0 and the second double-pole triple-throw switch is set to position 1. The charging capacitor discharges to form a surge current and injects it into the ground lead of the core clamp. Under the action of electric heating, the low-impedance grounding point is converted into a high-impedance grounding point.

[0012] Step 3: After the grounding point is converted to a high-impedance state, the first double-pole triple-throw switch is set to position 1, and the second double-pole triple-throw switch is set to position 2. The power frequency AC excitation output by the voltage regulator is injected into the grounding lead of the core clamp to actively stimulate partial discharge at the high-impedance grounding fault point.

[0013] Step 4: Place three ultrasonic sensors on the wall of the transformer box and couple the high-frequency current sensor to the ground lead of the core clamp. The ultrasonic sensors and high-frequency current sensors collect acoustic and electrical signals and transmit them to the signal processor. After processing, they are transmitted to the all-in-one machine for display and positioning.

[0014] 3.Beneficial effects: This invention solves the problem that existing conventional detection methods are unable to locate the location of multiple grounding faults in transformer core clamps. In the transformer's low-impedance grounding state, the potential at the core clamp fault point is low, the partial discharge is weak, and the acquisition of acoustic and electrical signals is difficult. This invention uses capacitive current impulses to convert the low-impedance grounding state into a high-impedance grounding state. In the high-impedance grounding state, power-frequency AC excitation actively stimulates partial discharge at the high-impedance grounding fault point, and then collects acoustic and electrical information to accurately and efficiently locate the grounding fault point, facilitating subsequent transformer maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is an overall schematic diagram of the transformer core clamp grounding point detection device.

[0016] Figure 2 It is a schematic block diagram of a transformer core clamp grounding point detection device.

[0017] Figure 3 This is a schematic diagram of the combined acoustic and electrical positioning of the transformer core fault grounding point.

[0018] Figure 4 It is a schematic diagram of the waveforms collected by the combined acoustic and electrical positioning of the transformer core fault grounding point.

[0019] Figure 5 It is an integrated transformer core clamp grounding point detection device.

[0020] Explanation of the accompanying symbols: 1. Voltage regulator; 201. First double-pole triple-throw switch; 202. Second double-pole triple-throw switch; 3. Rectifier; 4. Charging capacitor; 501. First current-limiting resistor; 502. Second current-limiting resistor; 503. Third current-limiting resistor; 801. Industrial frequency AC output terminal; 802. Inrush current output terminal; 9. Whole machine power switch; 10. Acoustic and electrical signal input terminal. DETAILED DESCRIPTION

[0021] The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0022] The present invention provides a transformer core clamp grounding point detection device. This device addresses the problem of low potential at the core clamp fault point in the transformer's low-impedance grounding state, resulting in weak partial discharge and difficulty collecting acoustic and electrical signals. The device utilizes capacitive current surges to convert the low-impedance grounding state into a high-impedance grounding state. In the high-impedance grounding state, power-frequency AC excitation actively stimulates partial discharge at the high-impedance grounding fault point, allowing the acquisition of acoustic and electrical information to accurately and efficiently locate the grounding fault point.

[0023] Specific structure such as Figure 1 and Figure 2As shown, it includes a voltage regulator 1, the input end of the voltage regulator 1 is connected to the mains, and the output end is connected to the input end of the first double-pole triple-throw switch 201. When the knob is set to gear 0, its input and output ends are disconnected. When the knob is set to gear 1, the voltage regulator outputs an AC excitation of the same amplitude as the power frequency through the switch. When the switch is set to gear 2, the voltage regulator is connected to the rectifier 3 via the switch, and the industrial frequency AC is input to the rectifier 3. The rectifier 3 rectifies the AC output by the voltage regulator into DC and charges the charging capacitor 4. The positive and negative ends of the charging capacitor 4 are connected in parallel with the second double-pole triple-throw switch 202. When the charging capacitor 4 is fully charged, the second double-pole triple-throw switch 201 is set to gear 1, and the charging capacitor 4 outputs an impulse current to the outside through the second double-pole triple-throw switch 202. After the impulse is completed, the second double-pole triple-throw switch 202 is set to gear 2, and the residual energy of the capacitor is completely consumed by the resistor 503. The signal processor 6 collects the ultrasonic signal and the high-frequency current pulse signal collected by the ultrasonic sensor and the high-frequency current sensor, and transmits them to the all-in-one machine 7 after processing. The all-in-one machine 7 receives the sensor spatial position coordinates input by the screen and the acoustic and electrical signals input by the signal processor, outputs the ultrasonic signal and the high-frequency current pulse signal waveform, and locates the fault grounding point according to the spatial spherical formula algorithm.

[0024] When the transformer core clamp is grounded at low impedance, the potential of the core clamp is low, the partial discharge is weak, and the acquisition of acoustic and electrical signals is difficult. Therefore, a surge current is injected into the core clamp lead wire. Through the electrothermal effect of the large current, the low-impedance grounding state of the core clamp is converted to a high-impedance grounding state.

[0025] When transformer core clamps are grounded at high impedance, the potential inside them is high, making partial discharge (PD) more likely to occur and generating strong acoustic and electrical signals. This method uses power-frequency AC injected into the core clamp grounding lead to actively stimulate partial discharge at the high-impedance grounding point, thereby increasing the intensity of partial discharge at the grounding fault point.

[0026] In one embodiment, the present invention utilizes a combined acoustic and electrical location method to locate the fault grounding point. This method utilizes the acoustic and electrical signals generated by partial discharge to accurately and efficiently locate the transformer core clamp grounding fault point. This combined acoustic and electrical detection technology not only pinpoints the specific location of the transformer core clamp grounding fault point, but also provides excellent positioning due to the high frequency of the ultrasonic signal and high-frequency current pulses, minimizing interference from electromagnetic signals within the substation.

[0027] like Figure 3 and Figure 4 As shown in FIG, the specific method is as follows: a high-frequency current sensor and three ultrasonic sensors are used to detect the high-frequency current pulse signal and ultrasonic signal emitted by the partial discharge of the transformer core grounding fault point respectively. The position coordinates of the three ultrasonic sensors are set as follows: X i , Yi , Z i i=1, 2, 3, the time it takes for the ultrasonic wave to propagate from the ground fault point to the ultrasonic sensor is t 1, t 2, t 3. The time it takes for the high-frequency current pulse to propagate from the ground fault point to the high-frequency current sensor is t 0.

[0028] Since the propagation speed of electrical signals is the speed of light and is much greater than the propagation speed of ultrasonic signals, the first signal collected, S0, is a high-frequency pulse current signal, and the time it takes for the high-frequency current pulse signal to propagate from the fault point to the high-frequency current sensor is t 0≈0, then, we can approximately think that t Time 0 is the time when the core grounding fault point sends out the ultrasonic signal. By setting three ultrasonic sensors at different positions of the transformer shell, three ultrasonic signals S1, S2, and S3 are collected, and the time difference between them and the high-frequency current pulse signal is t 1 ,t 2 ,t 3, which is the propagation time of the ultrasonic signal from the fault point to the ultrasonic sensor. Using the spatial spherical formula: In the formula X i， Y i， Z i are the spatial coordinates of the three ultrasonic sensors, and V is the propagation speed of ultrasonic waves in transformer oil, which is about 1400 m / s. The two intersection points ( X a , Y a , Z a ), ( X b , Y b , Z b ), where the coordinates of the intersection point inside the transformer are the spatial coordinates of the grounding fault point.

[0029] In one embodiment, when high-impedance partial discharge is induced by power-frequency AC excitation, the first current-limiting resistor 501 is used to reduce the breakdown current, limit the fault power, and prevent the fault from expanding. The second current-limiting resistor 502 is used to limit the inrush current generated when the capacitor is charged to prevent damage to the device.

[0030] In one embodiment, Figure 5 As shown, the transformer core clamp grounding point detection device is an integrated design. Its exposed components mainly include the knob adjustment switch of the voltage regulator 1, the first double-pole triple-throw switch 201, the second double-pole triple-throw switch 202, the all-in-one device 7, the power frequency AC output terminal 801, the inrush current output terminal 802, the whole device power switch 9, and the acoustic and electrical signal input terminal 10. The remaining components are integrated internally.

[0031] The present invention also provides a method for detecting the grounding point of a transformer core clamp, using the transformer core clamp grounding point detection device, comprising the following steps: Step 1: Turn on the power supply, change the effective value of the AC voltage through the voltage regulator 1, set the first double-pole triple-throw switch 201 to gear 2, and convert the industrial frequency AC into DC through the rectifier 3 to charge the charging capacitor 4.

[0032] Step 2: After the charging capacitor 4 is fully charged, the first double-pole triple-throw switch 201 is set to gear 0, and the second double-pole triple-throw switch 202 is set to gear 1. The charging capacitor 4 discharges to form a surge current and injects it into the grounding lead of the core clamp, converting the low-impedance grounding point into a high-impedance grounding point under the action of electrothermal energy.

[0033] Step 3: After the grounding point is converted to a high-impedance state, the first double-pole triple-throw switch 201 is set to position 1, and the second double-pole triple-throw switch 202 is set to position 2. The power frequency AC excitation output by the voltage regulator 1 is injected into the grounding lead of the core clamp to actively stimulate partial discharge at the high-impedance grounding fault point.

[0034] Step 4: Place three ultrasonic sensors on the wall of the transformer box, and couple the high-frequency current sensor to the core ground lead. The ultrasonic sensors and high-frequency current sensors collect acoustic and electrical signals and transmit them to the signal processor 6. After processing, they are transmitted to the all-in-one machine 7 for display and positioning.

[0035] When the present invention locates the fault point of a transformer, the positioning can be completed without disassembling the transformer casing.

[0036] The present invention utilizes capacitor impulse current excitation and power frequency AC excitation to achieve conversion from a low-resistance state to a high-resistance state and enhance partial discharge in the high-resistance state, making it easy to monitor ultrasonic signals at the transformer casing.

Claims

1. A transformer core clamp grounding point detection device, comprising a voltage regulator (1), wherein the input end of the voltage regulator (1) is connected to the mains, and is characterized in that: The output end is connected to the input end of the first double-pole triple-throw switch (201); when the knob is set to gear 0, the input and output ends are disconnected; when the knob is set to gear 1, the voltage regulator outputs an AC excitation of the same power frequency as the output end through the switch; when the first double-pole triple-throw switch (201) is set to gear 2, the voltage regulator is connected to the rectifier (3) through the switch; the rectifier (3) is connected to the charging capacitor (4); the positive and negative ends of the charging capacitor (4) are connected in parallel to the second double-pole triple-throw switch (202); when the second double-pole triple-throw switch (201) is set to gear 1, the charging capacitor (4) is connected to the output end; The surge current is outputted outwardly through the second double-pole triple-throw switch (202), the second double-pole triple-throw switch (202) is placed in gear 2, the charging capacitor is connected to the third current limiting resistor (503), the signal processor (6) collects the ultrasonic signal and the high-frequency current pulse signal collected by the ultrasonic sensor and the high-frequency current sensor, and transmits them to the all-in-one machine (7) after processing. The all-in-one machine (7) receives the spatial position coordinates of the sensor input from the screen and the acoustic and electrical signals input from the signal processor, outputs the ultrasonic signal and the high-frequency current pulse signal waveform, and locates the fault grounding point according to the spatial spherical formula algorithm.

2. The transformer core clamp grounding point detection device according to claim 1, characterized in that: A first current limiting resistor (501) is provided between the first double-pole triple-throw switch (201) and the industrial frequency AC excitation output.

3. The transformer core clamp grounding point detection device according to claim 1, characterized in that: A second current limiting resistor (502) is connected in series between the rectifier (3) and the charging capacitor (4).

4. The transformer core clamp grounding point detection device according to any one of claims 1 to 3, characterized in that: The fault grounding point of the transformer is located by combining acoustics and electricity. The specific method is as follows: a high-frequency current sensor and three ultrasonic sensors are set to detect the high-frequency current pulse signal and ultrasonic signal emitted by the partial discharge of the transformer core clamp grounding fault point respectively. By setting three ultrasonic sensors at different positions of the transformer shell, three ultrasonic signals S1, S2, and S3 are collected, and the time difference between them and the high-frequency current pulse signal is calculated. t 1 ,t 2 ,t 3. is the propagation time of the ultrasonic signal from the fault point to the ultrasonic sensor, using the spatial spherical formula: In the formula X i， Y i， Z i are the spatial coordinates of the three ultrasonic sensors, V is the propagation speed of ultrasonic waves in transformer oil, and the two intersection points ( X a , Y a , Z a ), ( X b , Y b , Z b ), where the coordinates of the intersection point inside the transformer are the spatial coordinates of the grounding fault point.

5. The method for detecting the grounding point of a transformer core clamp according to claims 1-4, using the device for detecting the grounding point of a transformer core clamp according to any one of claims 1-4, characterized in that: The following steps are involved: Step 1: Turn on the power supply, change the effective value of the AC voltage through the voltage regulator (1), set the first double-pole triple-throw switch (201) to gear 2, and convert the industrial frequency AC into DC through the rectifier (3) to charge the charging capacitor (4); Step 2: After the charging capacitor (4) is fully charged, the first double-pole triple-throw switch (201) is set to gear 0, and the second double-pole triple-throw switch (202) is set to gear 1, the charging capacitor (4) is discharged to form a surge current and the surge current is injected into the ground lead of the core clamp, and the low-impedance grounding point is converted into a high-impedance grounding point under the action of electrothermal heating; Step 3: After the grounding point is converted into a high-impedance state, the first double-pole triple-throw switch (201) is set to gear 1, and the second double-pole triple-throw switch (202) is set to gear 2, and the power frequency AC excitation output of the voltage regulator (1) is injected into the grounding lead of the core clamp to actively stimulate partial discharge at the high-impedance grounding fault point; Step 4: Place three ultrasonic sensors on the wall of the transformer box, and couple the high-frequency current sensor to the ground lead of the core clamp. The ultrasonic sensors and high-frequency current sensors collect acoustic and electrical signals and transmit them to the signal processor (6). After processing, they are transmitted to the integrated machine (7) to complete display and positioning.

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