Commissioning and Testing of Protection Relays for Distribution Systems

Protection relays have long been used to protect electrical equipment and networks. During the last 30 years, the design of protection relays has changed significantly with conventional electromagnetic relays being replaced by numeric relays, alternatively known as IEDs (intelligent electronic devices). Modern IEDs are software based and offer many programmable functions within a single relay. To ensure that protection relays meet the requirements of safety, reliability and security of modern power system protection, the protection relay must be adequately tested and proven 'fit for purpose'. When field testing power system protection relays for commissioning purposes, the question of what level of testing is required to confidently place plant into service is highly debatable. As practicing professional engineers, we are often faced with the competing restraints of cost, time and quality when making decisions to design, procure, test and commission protection relays. This project investigates the need for engineering decision making to find intelligent and justifiable decisions for the commissioning and testing of modern IEDs. The dissertation outlines the literature review, protection philosophies used within distribution networks, justifiable engineering strategies and engineering decision making for the selection of, and testing and commissioning of protection relays. A review of Australian and international standards was conducted to identify testing requirements for protection relays, to propose a defendable and robust approach for testing numeric relays and to provide guidelines for effective and efficient testing. Considering the proposed testing philosophy, a review of current industry practices has been conducted and the results published in appendix B2. The outcome of this investigation is to provide sound engineering guidelines around the field testing requirements to confidently and safely commission power system protection relays