Purpose/Aim
Acoustic detection of partial discharges is one of the major methods for detecting partial discharge in transformer. The arrangement of ultrasonic sensors is a key factor affecting the sensitivity of the sensor. When studying the optimal arrangement of ultrasonic sensors, it is necessary to know the ultrasonic characteristics in the transformer. At present, there are little research on the ultrasonic propagation characteristics and distribution of ultrasonic of large transformer.
Experimental/Modeling methods
This paper established a 3D simulation model of a 220kV power transformer by the COMSOL Multiphysics, based on the high-order discontinuous Galerkin method, for studying the ultrasonic wave propagation. It coupled two physics interfaces, and modeled sound-structure interaction, involving solid mechanics and pressure. The propagation characteristics of the acoustic waves at different media interfaces and the distribution law of sound pressure in the transformer are studied. And 10 sensor installation positions and 20 sound source positions were selected to compare the detection sensitivity of sensors at different locations.
Results/discussion
The acoustic pulse generated by the partial discharge propagates through the transformer to the sensor, it would be deformed and attenuated due to the different propagation distance and medium. However, the distribution of ultrasonic waves on the transformer tank has general law in different materials such as iron and transformer oil. All of them take the vertical mapping point from the partial discharge source to the transformer tank wall as the center of the circle and spread to the surrounding. And according to the simulation results higher detection coverage was achieved when the sensor was mounted on the center of the long side.
Conclusions
The simulation in this paper visualized the propagation path and acoustic waveforms, and analyzed the propagation characteristics of ultrasonic wave in the transformer. Besides, the optimal arrangement of ultrasonic sensors was proposed. It provided the basis for partial discharge ultrasonic detection.

ultrasonic,power transformer,partial discharge,multiphysics,discontinuous Galerkin method