The combined protection relay is one of the relays, which basically designed to protect the user device from negative phase sequence, single phasing and also the power distribution line with the help of a differential relay. The negative phase sequence relay basically protects the devices against the reverse phase sequence and also against the unbalance phase sequence generated due to unbalance loading. Single phasing relays protect the device against the phase failure. The differential relay protects the zone of the transmission line.The specialty in this project is the design is made on 89c51 micro controller, which is faster and controls all the relays. This is static relay so no much mechanical movement is there. The response time is very fast and can be programmed for any value. The great advantage of programming is available to the user.  

1. Necessity of Starter A Squirrel cage induction motor just before starting is similar to a poly phase transformer with a short-circuited secondary. If normal voltage is applied to the stationary motor then, as in the case of a transformer, a initial current, to the turn of 5 to 6 times the normal current or…