MICROPROCESSOR
BASED
IMPEDANCE RELAY

ABSTRACT

With growing complexity of modern power systems, faster, more accurate and reliable than existing protection schemes have become essential. Microprocessor based protective schemes are the latest development in this area.
These micro processor based schemes generally deliver better performance at relatively lower cost and with simpler construction because the operation of the scheme depends largely on programming the micro processor and little on the actual hardware connections.
In this paper the implementation of an impedance relay using 8085 microprocessor is described. That kit used for this purpose is Vinytics VMC 8506 which has an inbuilt ADC interface based on ADC0809 chip and also some relays which can be turned on or off by providing simple 8085 instructions. The relay is operated in three zones with the required delay based on impedance.