Field experience using a microprocessor relay to protect a 14,000 hp motor

The protective relays discussed in this paper along with individual solid-state relaying protect a 14,000 hp 4-pole compressor induction motor. All protection is located in an outdoor breaker cubicle located at a Gulf coast petrochemical plant without the benefit of HVAC. The protection scheme was designed so that all fault types and abnormal operating conditions are properly detected and cleared. The installation includes unique protection functions for locked rotor protection, blown fuse detection, customized logic for the upstream breaker tripping, customized relay display, and condition monitoring of the primary equipment (breaker, current transformer (CT), voltage transformer (VT) etc). A novel approach using non-saturating current and voltage sensors is also discussed in this paper.