Power Transformer PD Detection Method And Interference Suppression

      The power monitoring of partial discharge of power transformers mainly includes the monitoring of the internal charge distribution, the tracking monitoring of electrical signals, and the insulation performance monitoring of insulating materials.

I UHF PD Monitoring

      UHF partial discharge monitoring mainly uses the powerful data analysis ability of the computer to effectively track the lost charge through the difference between the input and output of the charge at both ends of the transformer, so that the damaged part of the insulation layer can be seen intuitively timely maintenance by technicians. The disadvantage of this method is that due to the complexity of the internal structure of the power transformer and the collision in the flow of charge, it will bring certain errors to the measurement and data collection of the computer. 

II Over-frequency Broadband PD Monitoring

      Over-frequency broadband partial discharge monitoring method is suitable for partial discharge detection of large industrial transformers. Using the high scan of the frequency spectrum and the small probability of misalignment, it is possible to simultaneously monitor the insulation of the transformer in a larger area at the same time. Because this method has the advantages of wide monitoring range, full coverage, and large amount of collected information, it is widely used in the partial discharge monitoring of transformers in large-scale operation equipment.

III Non-electrical Measurement of PD 

      The non-electrical measurement method of partial discharge was originally applied to the biological and chemical aspects, mainly to detect and track the micro-charge in the living body. Due to the development of modern science and technology, various disciplines can communicate well with each other, especially among disciplines with relevant research content, and their professional measurement methods can be very common. This method is to use chemical quantitative analysis to analyze the chemical cycle through the determination of the chemical properties of the ions in the transformer, thereby judging the area with active chemical properties. Close to the non-electrical measurement method are the transformer oil chromatography online monitoring method and the transformer oil hydrogen concentration online monitoring, collectively referred to as the three major chemical methods of transformer partial discharge monitoring. 

IV PD Optical Fiber Technology Detection Method

      Optical fiber technology is a relatively successful method of ultrasonic detection. The optical fiber technology is connected with the local detection of the power transformer, and the technological innovation of the local detection of the transformer is realized. The use of optical fiber to detect partial discharge has obvious advantages: the fiber is propagated unidirectionally in the internal path of the transformer, thereby avoiding the repetition of partial discharge signals and preventing the secondary impact on the composite circuit. The measuring principle is that when the insulating layer of the power transformer is broken down, the ultrasonic signal emitted by the discharge part will propagate along the path that the optical fiber passes through. In this process, collision of charge volume will not occur, thereby avoiding additional loss of charge. When the electric charge propagates to a certain degree, the external modem connected to the computer will extract the electrical signal generated by the partial discharge, and convert it into data information and import it to the computer connected to it, and then calculate the high-speed quantitative relationship through the computer. 

V Infrared Detection Method of PD 

      Infrared detection has also been applied to the detection of partial discharges in power transformers. Infrared detection is based on the temperature rise of the partial discharge point, using the thermal imaging principle of the infrared detector to achieve hot spot measurement. However, due to the complexity of the transformer structure and heat transfer process, it is very difficult to directly detect partial discharges located inside the transformer body using infrared imaging methods. At present, the infrared detection of the transformer is effective for the external faults of the transformer (including poor conductor connection, box eddy current caused by magnetic leakage, cooling device failure and transformer bushing failure, etc.).

Electromagnetic Interference and Suppression of PD Detection

      The partial discharge detection of the transformer can effectively reflect the actual insulation of the transformer, but in the actual measurement, due to the constraints of external environmental factors, the measurement results are reduced to a large extent, even in severe cases, the measurement work cannot continue . 

      The factors that cause partial discharge detection not to be performed normally are various, and they can be divided into different categories according to different classification conditions. Common interferences include periodic interference, pulsed interference, white noise interference, laboratory shielding interference, etc. Take strong targeted suppression measures for different types of interference. As far as the current interference suppression situation is concerned, a completely effective control method has not been found. The existing measures are more or less restricted by some unfavorable factors, and the application is relatively narrow. According to relevant professional reports, a more advanced digital anti-interference processing system is currently being established. With the help of modern scientific technical means, good progress has been made. I hope that with the continuous development of related scientific research work, we can develop a targeted a new type of transformer partial discharge anti-interference system with strong and wide application range.

      The purpose of partial discharge detection is to achieve a better guarantee for the safety performance of power transformers. With the continuous improvement of computer technology and digital signal processing technology in the power industry, partial discharge detection can provide sufficient data guarantee that it will be widely used in the future.

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