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Power System Protection Relay Settings Customized to Fit Your Needs


Authored by: Gregory Bee, Settings Engineer at Power Grid Engineering

System protection engineers play an incredibly important role in the safe and reliable operation of the power grid. The primary focus of system protection engineers is to develop protective relay settings and schemes that will appropriately protect system equipment during adverse system events. These events, which might require a protective operation, include unstable power swings, power-line faults, or equipment failures. When appropriately set, relays will operate to de-energize the minimum amount of equipment necessary to maintain grid stability and equipment integrity during an adverse system event, while also avoiding unnecessarily de-energizing equipment during a non-protective event. Equipment integrity, grid stability, and most importantly, the safety of the public and utility workers depends on an aptly designed and accurately operating power system protection.

While some relay setting design criteria is based on reliability standards dictated by regulating entities, like the North America Electric Reliability Corporation (NERC) or IEEE standards, many design considerations come from decades of industry best practices. At the individual utility level, a system protection department will have its own setting philosophy based on many different factors. Some of these factors include legacy equipment models already in service, event restoration procedures, or tolerance for potentially nuisance protective operations. Special consideration is given to past events for both correct and incorrect operations on specific portions of the utility system. Over decades, minor adjustments from system events and company practices evolve into a set of protection standards that is unique to each individual transmission, generation, or distribution owner. For example, a line feeding a critical service area like a hospital, requires deviating from otherwise typical protection criteria. In such an instance, relay settings should be selective enough to only trip for faults associated with the hospital feed to prevent unnecessary service interruptions.

Considering how specific utility protection schemes can be, relay settings are often one of the last services to be contracted to an outside engineering service. There can be the valid concern of receiving a generic product that does not follow the utility’s established protection philosophies. Increasingly complex protection automation schemes and newly mandated reliability standards such as NERC PRC-027 can also add additional workloads to a utility’s existing system protection department. This is where Power Grid Engineering’s system protection team can assist in developing fully customized protection settings that include the utility’s unique protection philosophy and setting criteria. The system protection team members at PGE each bring from five to twenty-five years of experience from utility, consulting, and academic backgrounds. With a broad variety of experience in transmission, distribution, and generation protective relaying, PGE’s team uses knowledge and experience from multiple systems and setting philosophies to produce a fully tailored product to fit your company’s protection needs.