Commissioning of Protective Relay Systems

Performing tests on individual relays is a common practice for relay engineers and technicians. Most utilities have a wide variety of test plans and practices. However, properly commissioning an entire protection system, not just the individual relays, presents a challenge. This paper suggests a process for performing consistent and thorough commissioning tests through many sources: breaking out relay logic into schematic drawings; using SER, metering, and event reports from relays; simulating performance using end-to-end testing and lab simulations; and utilizing other tools, including synchrophasor measurements. We examine and suggest approaches for commissioning several applications: distribution bus protection, short line protection using communications-aided tripping, main-tie-main scheme, line and transformer differential protection. Finally, we propose that, while 100% commissioning certainty may not be possible, we can approach 100% by integrating event report analysis to validate our commissioning strategy.

I. Introduction

Protective relays now perform many functions besides protection. The advantages that modern microprocessor-based relays provide over traditional relays are well documented. These advantages include fault location, event reports, and programmable logic that allow many functions to be included in one device, thus saving hardware and wiring costs. One important complication of the technology shift is the increasing portion of the protection system design that resides in algorithms and logic in relays.