Protection of remotely located motors

This paper discusses application issues for motors located 1000 feet or more from protective relays. Differential protection of the motor, ground fault protection of the motor, thermal protection of the motor, and selectivity between motor and cable faults are discussed. Possible solutions for each one of these protection methods are presented, with a discussion of advantages and disadvantages for each method. Specific application concepts addressed are CT dimensioning, sizing CT secondary leads to maintain adequate CT performance, installing differential and ground fault protection at the motor location, installing thermal protection at the motor location, and using digital communications to transmit thermal data from the motor to the protective relay.