Some lessons learned from commissioning substation and medium voltage switchgear equipment

This paper presents some general procedures for the proper inspection, testing, and start-up of critical, but often overlooked, electrical items in substations and medium voltage switchgear commonly found in petro-chemical facilities. The paper emphasizes procedures for protective relay and circuit breaker control circuit testing. Practical methods for testing current and potential circuits, which are the critical sensing inputs for most protective relaying, are discussed. Recommendations are made for confirming control circuits to ensure that protective equipment operates as intended. Finally, examples of common commissioning oversights are presented to emphasize the thoroughness needed to avoid potentially damaging consequences.