Fundamental Reliability Considerations in the Design, Manufacturing and Application of Multifunction Digital Relays for Generator Protection

A major concern in the application of multifunction digital relays for the protection of generators is that almost all the electrical protection, including both primary and the backup relay functions, are embodied in one digital package. The failure of that package results in the loss of virtually all generator electrical protection. This paper discusses how multifunction relays can be designed and manufactured to minimize such failures. It describes the role of self-diagnostics in determining the health of the relay. Most importantly, it proposes cost-effective application strategies which can be employed to survive an in-service multifunction relay failure without loss of generator protection.