Development of microcontroller based over-current relay controls

Abstract

This Project is about designing the controls of an Overcurrent relay using microcontroller. Relay is an electrical switch. Generally it operates on electromagnetic principle for switching action. Over current (OC) relay is a type of relay which performs its switching action based on an input current to it. When the input current exceeds a particular pick up value the relay operates. Microcontroller based relays are gaining popularity as these have no mechanical contacts. These can operate at very high speeds. Any kind of characteristics can be obtained by using these. In a typical microcontroller based relay there is a current transducer, a controller, current transformer and a circuit breaker. Microcontroller reads load current via CT, transducer and ADC. When current is above pickup it gives a signal to circuit breaker to trip. Microcontroller can be programmed to obtain IDMT characteristics