Advancement of Safety Features for Industrial Power System Operations and Control

For safe operation of electrical systems at various voltage levels, implementation of various interlocks is arguably as important as protective relaying. This paper chronicles the evolution of the various mechanical and electrical interlocks that build inherent safety in the operation of switchgear. This is accompanied by development of complex logics within the protective relays and their communications over fiber-optic networks that reduce the number of required control cable installations, the potential points of physical failure, and the ongoing maintenance effort. The paper begins with an overview of the industry practice common to most balanced, polyphase power systems. This is followed by specific features that apply to various types of switchgear.A case study of a state-of-the-art interlock system on a large oil and gas facility, where every electromechanical action of the switchgear interlocks is mimicked by the power management system, is discussed. This includes not only the mechanisms present within the switchgear at each voltage level, but those necessary across various voltage levels.This paper aims to simplify the understanding of power system interlocks and their interactions with protection and control systems by providing rule-of-thumb guidelines and innovative solutions incorporated in modern power systems, improving operational safety and reliability of the power systems.