Multi-parameter online monitoring method for internal defects of electromagnetic voltage transformer

Abstract

The invention relates to the technical field of power system monitoring and fault diagnosis, and discloses an electromagnetic voltage transformer internal defect multi-parameter online monitoring method, which comprises the following steps: S1, detecting a discharge arc light signal in a transformer by using a photomultiplier; s2, capturing a partial discharge ultrasonic signal in the mutual inductor by adopting an ultrasonic sensor; s3, monitoring voltage and current signals of the mutual inductor by using a current sensor; s4, comprehensive internal defect analysis is carried out on the mutual inductor according to the detected optical signals, ultrasonic signals and voltage and current signals, early discovery and early warning of internal defects of the voltage mutual inductor can be achieved through a multi-parameter online monitoring method, the overall operation efficiency and safety of an electric power system can be improved, and the potential safety hazard of the electric power system can be reduced. Through the real-time and comprehensive monitoring, the maintenance cost and the potential risk caused by the fault of the voltage transformer can be greatly reduced.

Description

Technical Field

[0001] The invention relates to the technical field of power system monitoring and fault diagnosis, and in particular to a multi-parameter online monitoring method for internal defects of an electromagnetic voltage transformer. Background Art

[0002] In the power system, voltage transformer is an important power equipment, mainly used for voltage measurement and relay protection. With the increasing complexity and requirements of power systems, the stability and reliability of voltage transformers have become particularly important. Traditional voltage transformer detection methods mostly rely on regular physical inspections and maintenance, which is not only time-consuming and labor-intensive, but also unable to detect and solve problems in real time.

[0003] At present, partial discharge monitoring of electromagnetic voltage transformers mainly relies on periodic physical inspections and reactive maintenance based on specific symptoms. These methods have obvious limitations: slow response time, long intervals between periodic inspections, and inability to detect problems in a timely manner. Lack of real-time data, traditional methods lack real-time monitoring capabilities and cannot capture instantaneous partial discharge events. Inaccuracy is insufficient, and relying solely on external symptoms is often not enough to accurately diagnose internal partial discharge problems.

[0004] Although modern technologies such as fiber optic sensing and acoustic wave monitoring have been proposed for voltage transformer monitoring, there are still some gaps in practical applications: the lack of comprehensive monitoring solutions, current technologies focus on single parameters, and lack a comprehensive solution to simultaneously monitor multiple physical quantities related to partial discharge. High cost and complexity, advanced monitoring technologies are often costly and complex to install, which limits their popularity in small and medium-sized power facilities.

[0005] In view of the shortcomings of the prior art, the present invention proposes a new monitoring method, which comprehensively adopts the acoustic-optical-electrical joint detection technology and realizes comprehensive monitoring of various potential defects inside the voltage transformer through built-in photomultiplier tubes, ultrasonic sensors and current sensors. Summary of the invention

[0006] 1. Technical issues to be resolved In view of the shortcomings of the prior art, the present invention provides a multi-parameter online monitoring method for internal defects of an electromagnetic voltage transformer. The multi-parameter online monitoring method can not only achieve early detection and early warning of internal defects of the voltage transformer, but also improve the overall operating efficiency and safety of the power system. Through this real-time and comprehensive monitoring, the maintenance cost and potential risks caused by voltage transformer failure can be greatly reduced.

[0007] (II) Technical solution To achieve the above object, the present invention provides the following technical solution: a method for online monitoring of internal defects of an electromagnetic voltage transformer with multiple parameters, comprising the following steps: S1. Using a photomultiplier tube to detect the discharge arc light signal inside the transformer, and summarizing the detected multiple discharge arc light signals to form a discharge arc light signal set; S2, using an ultrasonic sensor to capture the partial discharge ultrasonic signal inside the transformer, and summarizing multiple ultrasonic signals to form an ultrasonic signal set; S3, using a current sensor to monitor the voltage and current signals of the transformer, and summarizing multiple voltage and current signals to form a voltage and current data set; S4. Comprehensively analyze the internal defects of the transformer by combining the optical signal, ultrasonic signal, voltage and current signals detected above.

[0008] Preferably, in S1, the expression of the discharge arc light signal set is:

[0009] In the above expression, Represents the discharge arc signal set, Represents the first discharge arc signal in the discharge arc signal set, Represents the discharge arc signal concentration A discharge arc signal, Indicates that there are a total of discharge arc signals A discharge arc signal.

[0010] Preferably, in S2, the expression of the ultrasonic signal set is:

[0011] In the above expression, represents the ultrasonic signal set, Represents the first ultrasonic signal in the ultrasonic signal set, Represents the ultrasonic signal concentration An ultrasonic signal, Represents the total number of ultrasonic signals An ultrasonic signal.

[0012] Preferably, in S3, the expression of the voltage and current data set is:

[0013] In the above expression, represents the voltage and current data set, Represents the current and voltage data collected for the first time in the voltage and current data set. Represents the voltage and current data set The current and voltage data collected are The current and voltage data in the voltage and current data set are collected in total Second-rate, Represents the time for collecting voltage and current data for the corresponding number of times, Represents the voltage data in the voltage and current data collected at the corresponding times, Represents the current data in the voltage and current data collected at the corresponding times.

[0014] Preferably, the photomultiplier tube is installed on the wall of the switch cabinet or the GIS casing, and 2 or more groups of photomultiplier tubes are installed around the voltage transformer to obtain the light signal emitted by the transformer discharge. The detection range of the photomultiplier tube includes the 230-400nm band with the largest corona discharge spectrum, and the photoelectric detection circuit includes a signal amplifier.

[0015] Preferably, the ultrasonic sensor is installed on the wall of the switch cabinet or the GIS housing, 1-2 ultrasonic sensors are arranged, the lower limit of the sensor detection intensity is not higher than 0.1mV, and the ultrasonic sensor system includes signal amplification and filtering functions.

[0016] Preferably, the current sensor is installed between the tail end of the primary winding of the voltage transformer and the grounding point, and a current sensor is installed on each phase voltage transformer winding. The current transformer adopts a Rogowski coil or a photoelectric current sensor. The lower limit of the current sensor detection accuracy is not higher than 0.1mA, and the detection accuracy of the current sampling system is not lower than 1kHz.

[0017] Preferably, in S4, the transformer defect identification method process is as follows: When the current sensor detects that the current has saturation characteristics, the peak value rises from 1mA to 50mA or more and remains for more than 10 cycles, and the waveform has narrow pulse width waveform characteristics, that is, there are high-frequency harmonic components exceeding 50Hz. This indicates that ferromagnetic resonance has occurred; Furthermore, the ferromagnetic resonance characteristics are determined based on the monitored voltage waveform. The frequency spectrum characteristics of the voltage waveform are obtained using the Fourier analysis method; If there are odd harmonic components such as 3 times (150Hz), 5 times (250Hz), 7 times (350Hz) in addition to the 50Hz component, it means that the resonance type is high-frequency resonance; If there are fractional frequency components such as 1 / 2 (25Hz), 1 / 3 (16.7Hz) in addition to the 50Hz component, it means that the resonance type is frequency division resonance; If the resonant component is mainly 50Hz and other frequency components are below 10%, it means that power frequency resonance occurs; If the frequency components are not dominated by 50 Hz and its integer (fractional) multiples, and the frequency components are widely distributed, it indicates that chaotic resonance occurs; At this time, the primary winding is heated, and infrared imaging detection shows that the primary winding of the transformer is heated as a whole, and the heating phase is the same as the current saturation phase. The photoelectric sensor does not find obvious discharge light signals.

[0018] Preferably, when the current sensor detects a pulse discharge waveform, or the ultrasonic sensor detects a discharge feature, and the discharge feature has acoustic-electric synchronization and is highly correlated with the power frequency signal cycle, indicating that local discharge occurs in the primary winding, the photoelectric sensor should not detect an obvious photoelectric signal.

[0019] Preferably, when the photoelectric sensor detects an obvious discharge signal and the current sensor detects a large current signal, a large arc discharge occurs in the transformer, and the arc is a turn-to-turn fault or a ground fault, and voltage fluctuations or a sharp drop occur.

[0020] Compared with the prior art, the present invention provides a multi-parameter online monitoring method for internal defects of an electromagnetic voltage transformer, which has the following beneficial effects: 1. The present invention comprehensively utilizes the detected optical signals, ultrasonic signals and current signals to conduct a comprehensive internal defect analysis of the transformer. Through the comprehensive analysis of these signals, the health status of the transformer can be judged more accurately. It integrates multiple characteristic parameter detection technologies, and can monitor and identify various potential defects inside the electromagnetic voltage transformer in real time, such as turn-to-turn short circuit, ferromagnetic resonance, etc., thereby greatly improving the operational safety and efficiency of the power system. Real-time impedance calculation not only helps to detect specific defects such as turn-to-turn short circuit and core saturation inside the transformer, but can also be used for early warning and fault diagnosis. The real-time impedance calculation can timely detect abnormal conditions inside the transformer by analyzing the changes in current and voltage signals, thereby providing accurate diagnostic information for maintenance personnel and realizing efficient management and maintenance of power equipment.

[0021] 2. The present invention can obtain multi-parameter indicators of the transformer, can comprehensively analyze the operating conditions of the transformer through multi-parameter data, obtain the precise state of the internal defects of the reactor, and can identify the types of voltage transformer defects including winding discharge, transformer resonance, etc. It can further accurately identify the type of resonance, and can distinguish between high-frequency resonance, power frequency resonance, frequency division resonance and chaotic resonance, covering the main defect types that may be encountered in the operation of the transformer.

[0022] 3. The present invention adopts the combined acoustic-optical-electrical detection technology, and realizes the comprehensive monitoring of various potential defects inside the voltage transformer through the photomultiplier tube, ultrasonic sensor and current sensor. The photomultiplier tube is used to detect the internal discharge arc signal, which can timely detect the local discharge phenomenon inside the voltage transformer; the ultrasonic sensor is used to capture the internal partial discharge ultrasonic signal, which helps to analyze and determine the specific location and degree of discharge; the current sensor is installed on the voltage transformer and is used to monitor its voltage and current signals in real time. By analyzing these signals, the real-time impedance of the voltage transformer can be calculated to determine whether there is a short circuit between turns or core saturation; this multi-parameter online monitoring method of the present invention can not only realize the early detection and early warning of internal defects of the voltage transformer, but also improve the overall operation efficiency and safety of the power system. Through this real-time and comprehensive monitoring, the maintenance cost and potential risks caused by voltage transformer failure can be greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The flowchart of the method for online monitoring of internal defects of an electromagnetic voltage transformer using multiple parameters in an embodiment of the present invention is shown in FIG.

[0024] Figure 2 This is a monitoring flow chart of a specific implementation method in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of 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.

[0026] See also Figure 1-2 , a method for online monitoring of internal defects of an electromagnetic voltage transformer by multiple parameters, comprising the following steps: S1. Use a photomultiplier tube to detect the discharge arc light signal inside the transformer, and summarize the multiple detected discharge arc light signals to form a discharge arc light signal set. This step is used to accurately capture the optical signal generated by the internal discharge, thereby realizing real-time monitoring of the discharge event; The expression of the discharge arc signal set is:

[0027] In the above expression, Represents the discharge arc signal set, Represents the first discharge arc signal in the discharge arc signal set, Represents the discharge arc signal concentration A discharge arc signal, Indicates that there are a total of discharge arc signals A discharge arc signal; The photomultiplier tube is installed on the wall of the switch cabinet or the GIS shell. Two or more photomultiplier tubes are installed around the voltage transformer to obtain the optical signal emitted by the transformer discharge. The position of the photomultiplier tube meets the coverage of the front and back sides of the transformer to avoid detection blind spots. The detection range of the photomultiplier tube includes the 230-400nm band with the largest corona discharge spectrum. The photoelectric detection circuit includes a signal amplifier to amplify the detected signal, which is conducive to subsequent signal analysis; The photomultiplier tube is used to detect the internal discharge arc signal and can promptly detect the partial discharge phenomenon inside the voltage transformer; Photomultiplier tubes can monitor the discharge phenomenon inside the voltage transformer in real time, and detect potential fault hazards in time by detecting the light signal generated by the discharge. This real-time monitoring capability helps to issue early warnings to avoid the expansion of faults or more serious problems. Photomultiplier tubes have high sensitivity and anti-interference ability, and can work stably in complex electromagnetic environments to ensure the accuracy of the detection results. This is crucial for accurately judging the internal state of the voltage transformer. Photomultiplier tubes use non-contact detection methods, without direct contact with the device under test, avoiding interference and errors that may be introduced in traditional methods. This detection method not only improves the safety of detection, but also reduces the difficulty and cost of operation. By real-time monitoring and analysis of the light signal generated by the discharge, the photomultiplier tube system can accurately locate and quantitatively analyze the position and degree of discharge. This helps operation and maintenance personnel to more accurately judge the health status of the equipment and formulate targeted maintenance plans and programs. Real-time monitoring and early warning functions help to promptly discover and deal with defects and hidden dangers inside the voltage transformer and avoid equipment failures or accidents caused by the expansion of defects. This can not only extend the service life of the equipment, but also improve the operational reliability and stability of the entire power system. Through real-time monitoring and early warning, it can reduce unnecessary downtime and maintenance time and frequency, and reduce the maintenance cost of equipment. At the same time, precise positioning and quantitative analysis functions can also help operation and maintenance personnel to formulate maintenance plans and programs more targeted, and further improve maintenance efficiency and quality. The application of photomultiplier tubes in the internal defect monitoring of electromagnetic voltage transformers has significant benefits and effects. It can not only improve the accuracy and safety of detection, but also realize real-time monitoring and early warning functions, providing strong guarantees for the safe and stable operation of the power system; S2. Use ultrasonic sensors to capture partial discharge ultrasonic signals inside the transformer, and aggregate multiple ultrasonic signals into an ultrasonic signal set. By analyzing these ultrasonic signals, internal partial discharge events can be accurately located and identified. The expression of the ultrasonic signal set is:

[0028] In the above expression, represents the ultrasonic signal set, Represents the first ultrasonic signal in the ultrasonic signal set, Represents the ultrasonic signal concentration An ultrasonic signal, Represents the total number of ultrasonic signals An ultrasonic signal; The ultrasonic sensor is installed on the wall of the switch cabinet or the GIS shell. 1-2 ultrasonic sensors are arranged. The ultrasonic sensor is used to capture the internal partial discharge ultrasonic signal. It has sufficient sensitivity and anti-interference ability and can effectively receive the discharge signal in the working frequency band of 20kHz-100kHz. The sensor has sufficient sensitivity to detect the weak signal generated by partial discharge, and the lower limit of the detection intensity is not higher than 0.1mV. The ultrasonic sensor system includes functions such as signal amplification and filtering to improve the signal-to-noise ratio of the signal and accurately capture the partial discharge signal; Ultrasonic sensors are used to capture internal partial discharge ultrasonic signals, which helps to analyze and determine the specific location and extent of the discharge; Ultrasonic sensors detect by capturing internal partial discharge ultrasonic signals without direct contact with the device under test. This non-contact detection method avoids the interference and errors that may be introduced in traditional methods and improves the accuracy of detection. Ultrasonic sensors have sufficient sensitivity to detect weak signals generated by partial discharge, and the lower limit of detection intensity is not higher than 0.1mV. At the same time, it has strong anti-interference ability and can work stably in complex electromagnetic environments to ensure the reliability of detection results. By arranging 1-2 ultrasonic sensors, the discharge phenomenon inside the electromagnetic voltage transformer can be monitored in real time. When partial discharge occurs, the sensor can quickly capture abnormal signals and issue an early warning to provide timely information support for operation and maintenance personnel. The ultrasonic sensor system includes functions such as signal amplification and filtering to improve the signal-to-noise ratio of the signal and accurately capture partial discharge signals. By analyzing and processing the captured signals, the precise positioning and quantitative analysis of the discharge position and degree can be achieved, which helps operation and maintenance personnel to more accurately judge the health status of the equipment. The real-time monitoring and early warning functions help to timely discover defects and hidden dangers inside the electromagnetic voltage transformer and avoid equipment failures or accidents caused by the expansion of defects. This can not only extend the service life of the equipment, but also improve the operational reliability and stability of the entire power system. Through real-time monitoring and early warning, it can reduce unnecessary downtime and maintenance time and frequency, and reduce equipment maintenance costs. At the same time, precise positioning and quantitative analysis functions can also help operation and maintenance personnel to formulate maintenance plans and programs more targeted, further improving maintenance efficiency and quality. The application of ultrasonic sensors on the wall of the switch cabinet or the GIS casing has significant benefits and effects on the internal defect monitoring of electromagnetic voltage transformers. It can not only improve the accuracy and reliability of detection, but also realize real-time monitoring and early warning functions, providing strong guarantees for the safe and stable operation of the power system; S3. Use current sensors to monitor the voltage and current signals of the transformer, and summarize multiple voltage and current signals to form a voltage and current data set, so as to calculate the real-time impedance of the transformer. The change of real-time impedance is the key indicator to determine whether the transformer has defects. The expression for the voltage and current data set is:

[0029] In the above expression, represents the voltage and current data set, Represents the current and voltage data collected for the first time in the voltage and current data set. Represents the voltage and current data set The current and voltage data collected are The current and voltage data in the voltage and current data set are collected in total Second-rate, Represents the time for collecting voltage and current data for the corresponding number of times, Represents the voltage data in the voltage and current data collected at the corresponding times, Represents the current data in the voltage and current data collected at the corresponding times; The current sensor is installed between the tail end of the primary winding of the voltage transformer and the grounding point. A current sensor is installed on each phase voltage transformer winding. The current transformer can use a Rogowski coil or a photoelectric current sensor to monitor its voltage and current signals in real time. The lower limit of the current sensor detection accuracy is not higher than 0.1mA, and the detection accuracy of the current sampling system is not less than 1kHz; The current sensor is used to monitor its voltage and current signals in real time. By analyzing these signals, the real-time impedance of the voltage transformer can be calculated to determine whether there is a turn-to-turn short circuit or core saturation. The present invention obtains a voltage signal from a metering coil in a secondary winding of a monitored voltage transformer for voltage harmonic analysis.

[0030] Further, the current sensor detection result is used to determine whether the transformer is abnormal. Under normal circumstances, the current of the primary winding of the monitored voltage transformer monitored by the current sensor is in the order of 1mA. When the primary winding is discharged, there will be a transient pulse signal, and when ferromagnetic resonance occurs, there will be iron core saturation, which is manifested in the appearance of a narrow pulse width current peak, and the current peak increases rapidly. At the beginning of resonance, its peak reaches 100mA, and the peak is about 50mA in steady state; Real-time impedance calculation not only helps detect specific defects such as inter-turn short circuit and core saturation inside the transformer, but can also be used for early warning and fault diagnosis. By analyzing the changes in current and voltage signals, the real-time impedance calculation can promptly detect abnormal conditions inside the transformer, thereby providing maintenance personnel with accurate diagnostic information and achieving efficient management and maintenance of power equipment; The current sensor can monitor the voltage and current signals of the voltage transformer in real time. By analyzing these signals, the real-time impedance of the voltage transformer can be calculated to determine whether there are defects such as inter-turn short circuit or core saturation. This real-time monitoring capability helps to timely detect potential fault hazards and issue early warnings to avoid the expansion of faults or more serious problems. The current sensor has high sensitivity and anti-interference ability, and can work stably in complex electromagnetic environments to ensure the accuracy of the detection results. This is crucial for accurately judging the internal state of the voltage transformer. The current sensor adopts a non-contact detection method, which does not require direct contact with the device under test, avoiding interference and errors that may be introduced in traditional methods. This detection method not only improves the safety of detection, but also reduces the difficulty and cost of operation. By real-time monitoring and analysis of voltage and current signals, the current sensor system can accurately locate and quantitatively analyze the discharge position and degree. This helps operation and maintenance personnel to more accurately judge the health status of the equipment and formulate targeted maintenance plans and programs. The real-time monitoring and early warning functions help to timely detect and deal with defects and hidden dangers inside the voltage transformer and avoid equipment failures or accidents caused by the expansion of defects. This can not only extend the service life of the equipment, but also improve the operational reliability and stability of the entire power system. The application of current sensors in the internal defect monitoring of electromagnetic voltage transformers has significant benefits and functions. It can not only improve the accuracy and safety of detection, but also realize real-time monitoring and early warning functions, providing strong guarantee for the safe and stable operation of the power system; S4. Comprehensively analyze the internal defects of the transformer by combining the optical signal, ultrasonic signal, voltage and current signals detected above. The health status of the transformer can be judged more accurately through the comprehensive analysis of these signals. The process of transformer defect identification method is as follows: When the current sensor detects that the current has saturation characteristics, the peak value rises from 1mA to 50mA or more and remains for more than 10 cycles, and the waveform has narrow pulse width waveform characteristics, that is, there are high-frequency harmonic components exceeding 50Hz. This indicates that ferromagnetic resonance has occurred; Furthermore, the ferromagnetic resonance characteristics are determined based on the monitored voltage waveform. The frequency spectrum characteristics of the voltage waveform are obtained using the Fourier analysis method; If there are odd harmonic components such as 3 times (150Hz), 5 times (250Hz), 7 times (350Hz) in addition to the 50Hz component, it means that the resonance type is high-frequency resonance; If there are fractional frequency components such as 1 / 2 (25Hz), 1 / 3 (16.7Hz) in addition to the 50Hz component, it means that the resonance type is frequency division resonance; If the resonant component is mainly 50Hz and other frequency components are below 10%, it means that power frequency resonance occurs; If the frequency components are not dominated by 50 Hz and its integer (fractional) multiples, and the frequency components are widely distributed, it indicates that chaotic resonance occurs; At this time, the primary winding is heated, and infrared imaging detection shows that the primary winding of the transformer is heated as a whole, and the heating phase is the same as the current saturation phase. The photoelectric sensor does not find obvious discharge light signals; When the current sensor detects a pulse discharge waveform, or the ultrasonic sensor detects a discharge feature, and the discharge feature has acoustic-electric synchronization and is highly correlated with the power frequency signal cycle, it indicates that there is a partial discharge phenomenon in the primary winding. At this time, the photoelectric sensor should not find an obvious photoelectric signal; When the photoelectric sensor detects an obvious discharge signal and the current sensor detects a large current signal, a large arc discharge occurs in the transformer. The arc is a turn-to-turn fault or a ground fault, and voltage fluctuations or a significant drop occur. The electromagnetic voltage transformer internal defect detection system of the present invention can not only timely detect problems such as inter-turn short circuit and partial discharge inside the transformer, but also greatly improve the safety and reliability of the power system, which is of great significance for preventing power accidents and ensuring the stable operation of the power system; It can obtain multi-parameter indicators of the transformer, comprehensively analyze the operating conditions of the transformer through multi-parameter data, obtain the precise state of the internal defects of the reactor, and identify the types of voltage transformer defects, including winding discharge, transformer resonance, etc. It can further accurately identify the type of resonance, and distinguish high-frequency resonance, power frequency resonance, frequency division resonance and chaotic resonance, covering the main defect types that may be encountered in the operation of the transformer; This multi-parameter online monitoring method can not only realize the early detection and early warning of internal defects of voltage transformers, but also improve the overall operation efficiency and safety of power systems. Through this real-time and comprehensive monitoring, the maintenance cost and potential risks caused by voltage transformer failures can be greatly reduced; By integrating multiple characteristic parameter detection technologies, it can monitor and identify various potential defects inside the electromagnetic voltage transformer in real time, such as turn-to-turn short circuit, ferromagnetic resonance, etc., thereby greatly improving the operating safety and efficiency of the power system.

[0031] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A multi-parameter online monitoring method for internal defects of an electromagnetic voltage transformer, characterized in that: The following steps are involved: S1. Using a photomultiplier tube to detect the discharge arc signal inside the transformer, and summarizing the detected multiple discharge arc signals to obtain a discharge arc signal set; S2, using an ultrasonic sensor to capture the partial discharge ultrasonic signal inside the transformer, and aggregating multiple ultrasonic signals to obtain an ultrasonic signal set; S3, using a current sensor to monitor the voltage and current signals of the transformer, and summarizing multiple voltage and current signals to form a voltage and current data set; S4. Comprehensively analyze the internal defects of the transformer by combining the optical signal, ultrasonic signal, voltage and current signals detected above.

2. The method for online monitoring of internal defects of an electromagnetic voltage transformer according to claim 1, characterized in that: In S1, the expression of the discharge arc light signal set is: In the above expression, Represents the discharge arc signal set, Represents the first discharge arc signal in the discharge arc signal set, Represents the discharge arc signal concentration A discharge arc signal, Indicates that there are a total of discharge arc signals A discharge arc signal.

3. The method for online monitoring of internal defects of an electromagnetic voltage transformer according to claim 2, characterized in that: In S2, the expression of the ultrasonic signal set is: In the above expression, represents the ultrasonic signal set, Represents the first ultrasonic signal in the ultrasonic signal set, Represents the ultrasonic signal concentration An ultrasonic signal, Represents the total number of ultrasonic signals An ultrasonic signal.

4. The method for online monitoring of internal defects of an electromagnetic voltage transformer according to claim 3, characterized in that: In S3, the expression of the voltage and current data set is: In the above expression, represents the voltage and current data set, Represents the current and voltage data collected for the first time in the voltage and current data set. Represents the voltage and current data set The current and voltage data collected are The current and voltage data in the voltage and current data set are collected in total Second-rate, Represents the time for collecting voltage and current data for the corresponding number of times, Represents the voltage data in the voltage and current data collected at the corresponding times, Represents the current data in the voltage and current data collected at the corresponding times.

5. The method for online monitoring of internal defects of an electromagnetic voltage transformer according to claim 4, characterized in that: The photomultiplier tube is installed on the wall of the switch cabinet or the GIS shell. Two or more photomultiplier tubes are installed around the voltage transformer to obtain the optical signal emitted by the transformer discharge. The detection range of the photomultiplier tube includes the 230-400nm band with the largest corona discharge spectrum, and the photoelectric detection circuit includes a signal amplifier.

6. The method for online monitoring of internal defects of an electromagnetic voltage transformer according to claim 5, characterized in that: The ultrasonic sensor is installed on the switch cabinet wall or GIS housing, 1-2 ultrasonic sensors are arranged, the lower limit of sensor detection intensity is not higher than 0.1mV, and the ultrasonic sensor system includes signal amplification and filtering functions.

7. The method for online monitoring of internal defects of an electromagnetic voltage transformer according to claim 6, characterized in that: The current sensor is installed between the tail end of the primary winding of the voltage transformer and the grounding point. A current sensor is installed on each phase voltage transformer winding. The current transformer adopts a Rogowski coil or a photoelectric current sensor. The lower limit of the current sensor detection accuracy is not higher than 0.1mA, and the detection accuracy of the current sampling system is not lower than 1kHz.

8. The method for online monitoring of internal defects of an electromagnetic voltage transformer according to claim 7, characterized in that: In S4, the transformer defect identification method process is as follows: When the current sensor detects that the current has saturation characteristics, the peak value rises from 1mA to 50mA or more and remains for more than 10 cycles, and the waveform has narrow pulse width waveform characteristics, that is, there are high-frequency harmonic components exceeding 50Hz; indicating that ferromagnetic resonance has occurred; Determine the ferromagnetic resonance characteristics based on the monitored voltage waveform; use Fourier analysis method to obtain the frequency spectrum characteristics of the voltage waveform; If there are 150Hz, 250Hz, and 350Hz odd harmonic components in addition to the 50Hz component, it means that the resonance type is high-frequency resonance; If there are fractional frequency components such as 25Hz and 16.7Hz in addition to the 50Hz component, it means that the resonance type is frequency division resonance; If the resonant component is mainly 50Hz and other frequency components are below 10%, it means that power frequency resonance occurs; If the frequency components are not dominated by 50 Hz and its integer multiples, and the frequency components are widely distributed, it indicates that chaotic resonance occurs; At this time, the primary winding heats up, which assists the infrared imaging detection in showing that the primary winding of the transformer is heating up as a whole, and the heating phase is the same as the current saturation phase; the photoelectric sensor does not find any obvious discharge light signal.

9. The method for online monitoring of internal defects of an electromagnetic voltage transformer according to claim 8, characterized in that: When the current sensor detects a pulse discharge waveform, or the ultrasonic sensor detects a discharge feature, and the discharge feature has acoustic-electric synchronization and is highly correlated with the power frequency signal cycle, it indicates that local discharge exists in the primary winding. At this time, the photoelectric sensor should not find obvious photoelectric signals.

10. The method for online monitoring of internal defects of an electromagnetic voltage transformer according to claim 9, characterized in that: When the photoelectric sensor detects an obvious discharge signal and the current sensor detects a large current signal, a large arc discharge occurs in the transformer. The arc is a turn-to-turn fault or a ground fault, and voltage fluctuations or a significant drop occur.

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