The energy based directional protection of transmission lines

In this paper we present an ultra high speed relay based on the energy function in the fault component. The fault direction can be held for a long time after the fault inception and which will not be influenced by the transient harmonics. To resolve the problems caused by the unbalanced situation in system swing, we propose an adaptive determination of fault direction. As a result, the speed and the security are both improved. Computer simulations with the Electromagnetic Transients Program (EMTP) are also included.