COMPUTER CO- ORDINATION OF O/C& E/F RELAYS WITH TWO LEVEL VOLTAGES ON IRAN POWER SYSTEM.

To operate protective relays correctly, Co-ordination of non unit relays specially overcurrent and earth fault protection is vital.Existing Co-ordination programs Can set the settings of the relays installed on a network having one level voltage. The aim of this paper is to present application of Co-ordination program for two level voltages incorporating transformer between two networks. In other work this program is applied to part of 400 KV and 230 KV network of Iran. The results of such application are Compared with the existing one which has been set manually. Relays on different locations of the chosen network are selected according to a classification based on connection of the network with other Darts of the Iran interconnected Analyses are, made for the relays and of that which is directly useful for power industry are given.