MICROCONTROLLER BASED FREQUENCY RELAY

Abstract

Frequency is an important operating parameter of power system. Frequency of a power system remains constant if sum of all loads plus losses equals total generation in the system. However, frequency starts to decrease if total generation is less than the sum of loads and losses. On the other hand, the system frequency increases if total generation exceeds the sum of loads and losses. The frequency changes that can be tolerated in a system are governed by the characteristics of the rotating equipment in the system. Reliable frequency measurements are therefore a pre-requisite for effective power system protection and control. These measurements should produce frequency readings as accurately and as fast as possible. Typically, both under and over frequency relays are used for Generator protection, Feeder protection Load shedding, EHV line schemes, Synchronism check and so on. A micro controller (8051) based frequency relay has been developed utilizing Zero crossing technique and also simulation of one of the frequency measurement technique, namely `Demodulation' method has been incorporated in this dissertation.