Numerical Simulation of Overpressure Caused by Arcing Faults Within an On-Load Tap Changer

Abstract

In recent years, serious explosion and fire accidents caused by intertap short-circuit faults inside converter transformer on-load tap changers have occurred continually, which has attracted great interest from grid companies, equipment manufacturers and researchers. When a short-circuit fault occurs in an on-load tap changer, the arc rapidly vaporizes the nearby insulating oil to a gas bubble, resulting in a sudden pressure rise in the oil compartment. However, due to a long-standing lack of understanding and defects in simulation methods, existing theoretical methods have difficulty accurately describing characteristics such as changes in oil pressure under arc fault conditions. This paper simulates the flow and structural fields of the on-load tap changer under fault conditions by establishing a coupled fluid-solid physical field model. The results of the calculations show that the on-load tap changer oil pressure rises sharply for a short period of time during a fault and then pulses continuously and decreases slowly. The investigation in this paper has certain academic significance and application meaning on the identification of tap changer faults and the design and optimization of the structure.