FEM Simulation and Test Verification of PD Ultrasonic Signal Propagation in a Power Transformer Model
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ORIGINAL ARTICLE
FEM Simulation and Test Verification of PD Ultrasonic Signal Propagation in a Power Transformer Model Zan Wang1 · Chaofei Gao2 · Liwei Zheng1 · Jikun Ren3 · Wei Wang1 · Yushuai Zhang1 · Shijie Han1 Received: 27 November 2019 / Revised: 31 August 2020 / Accepted: 15 September 2020 © The Korean Institute of Electrical Engineers 2020
Abstract Ultrasonic signals will be generated when partial discharge occurs in internal insulation faults in large oil immersed power transformers: because the ultrasonic signal has strong anti-interference ability and has no direct electromagnetic contact with the equipment, it is widely used in transformer fault detection and positioning. In this paper, the finite element method (FEM) is used to simulate the ultrasonic signal in a 35 kV power transformer. The influence of transformer case on ultrasonic signal propagation is considered, and the propagation law of the ultrasonic signal inside the transformer is obtained. Fabry–Pérot (F–P) fibre acoustic sensors with a centre frequency of 28 kHz were fabricated. A partial discharge detection test was carried out in a 35 kV transformer winding model using the F–P sensors. The test results show that the ultrasonic waveform detected by the F–P sensors are in good agreement with the simulation results, and the propagation of the ultrasonic wave inside the transformer is verified. It lays a foundation for detecting and locating PDs in power transformer by F–P acoustic sensors. Keywords Power transformers · Partial discharge · FEM · Propagation property
1 Introduction The insulation condition monitoring, diagnosis, and defect location of the oil-immersed power transformer and the timely arrangement of its maintenance are key measures used to reduce transformer failures and ensure the safe operation of power systems. Partial discharge (PD) is one of the key indicators of insulation condition in power transformers [1–3]. When PD occurs, ultrasound signals will be generated, the PD can be detected and located by detecting ultrasonic signals by multiple sensors. Due to the complicated internal structure of large power transformers, especially when PD occurs in windings with weak transformer insulation, the propagation of ultrasonic signals will be affected by coils, iron cores, and insulating paperboard, which makes * Chaofei Gao [email protected] 1
State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
2
School of Automation, Beijing Information and Technology University, Beijing 100192, China
3
Gaoyi Power Supply Company, State Grid Hebei Provincial Power Crop, Shijiazhuang 051330, Hebei, China
PD detection and positioning more difficult [4–7]. Therefore, PD detection and positioning in transformer windings is a very meaningful, but challenging, task. In recent years, due to the high precision of the Finite Element Method (FEM) and its ability to deal with various complex models and complex boundary conditions, the
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