Design and Analysis of a New Pressure Relief Valve for Oil-Immersed Electrical Equipment

Abstract

Internal arcing in oil-immersed electrical equipment is inevitable and of great danger. Transient overpressure should be released by protectors quickly and controllably. Currently available pressure relief valves cannot fully protect the electrical equipment due to mismatch between insufficient relief capacity with correspondingly weak valve structure and increasing arcing energy in upgrading electrical systems. Additionally, flaming possibility of ejected high-temperature oil–gas mixture is distinct, and retained oil in an oil tank without any isolation may be ignited by the flame. Unfortunately, resealing of some existing single-outlet valves is out of control due to asymmetrical hydraulic pressure distribution on the valve plate which causes unstable valve plate movement. Therefore, a new pressure relief valve characterized by symmetrical outlets and improved pressure relief capacity was developed. The novel structure and function of the new valve was first introduced, and comprehensive analysis regarding dynamic performances, strength and fluid development during the relief process were conducted. Finally, a prototype was manufactured and tested on a specific arcing test system. The developed valve can well release the overpressure generated by a 6 MJ equivalent arcing fault without any flame during the entire relief process. Furthermore, the valve structure can withstand the pressure load, and valve plate can precisely reseal the oil tank due to optimized fluid pressure distribution. This research provides an optimized pressure relief valve and a design guide for improved pressure relief valve.