Power-System Protection in an Oil-Field Distribution System

Power-system protection for oil-field distribution systems consists of protection for electrical submersible pump (ESP) installations and their upstream electrical circuits. In this paper, a comprehensive protective-device coordination and an arc-flash hazard analysis are conducted for a large oil-field distribution system. Various protection schemes are investigated and compared. This paper focuses on three areas: ESP installation protection using switchboards, the protective-device coordination of upstream electrical circuits of ESP wells, and how to obtain the optimized protective-device settings for both protection and arc-flash-safety concerns. ESP installation protection using fuses is first addressed. ESP wells that cannot be protected by fuses are particularly investigated, and a motor controller used with a fuse can provide a better protection for such ESP wells. A motor control center (MCC) for two large water injection pumps is used as a case study for the protective-device coordination of upstream circuits of ESP wells. Nuisance tripping was experienced during a motor starting at a 1750-hp water injection pump. The investigation indicates that improper relay settings at the MCC were the root cause. The optimized protective-device settings can be achieved by conducting a protective-device-coordination study and an arc-flash hazard analysis by keeping both protection and arc safety in mind.