ABSTRACT
In some applications, combinations of protective relay functions, combinations of protective relays and control logic, or combinations of protective relays and timers provide enhanced fault detection, better protective device coordination, or improved security when compared to single-function protective relays. Some of the combinations are
Voltage-Controlled Time Overcurrent Relay Torque-Controlled Time Overcurrent Relay Logic-Controlled Instantaneous Overcurrent Relay Torque-Controlled Instantaneous Overcurrent Relay Logic-Controlled Overvoltage Relay Logic-Controlled Undervoltage Relay Logic-Controlled Distance Relay Current-Supervised Distance Relay Logic-Supervised Differential Relay Current-Supervised Differential Relay Current-Supervised Underfrequency Relay Dual Underfrequency Relays
A voltage-controlled time overcurrent relay is one that is not permitted to start to time out unless voltage falls below a threshold value for the voltage detector and current exceeds the setpoint of the overcurrent detector.
