A Proposed Circuit for Controlling the Reactive Power in Electrical Networks

This paper addresses some problems encountered in the electric networks under light load conditions. Some operation engineers prefer to leave the standby transformers continuously connected under such conditions to increase the reliability of the network Some others consider this strategy a valid method for improving the power factor especially with the wide use of underground cables in the networks. However, leaving the standby transformers may lead to many problems such as loosing relay coordination, high power losses and increase in the short circuit level. This paper presents a novel control circuit that can be implemented in any station to automatically control the connection/disconnection of the standby feeders. By this circuit, a large number of underground cables will be disconnected under light load without any impact on the system reliability. At the same time, the reactive power will be effectively reduced. It is very suitable for unmanned substations. The circuit is fully described and its features and implementation feasibility are discussed.