Post-fault analysis of operation of distance protective relays of power transmission lines

This paper deals with the post-fault analysis of operation of distance protective relays from the line terminals. The signals of the digital distance relays are processed in the off-line regime with the aim of evaluating the particular relay operation case. First, the program enables the emulation of the fault loop impedance measurements of the distance relays. Second, the two-end unsynchronized measurements of the relays are considered. The unknown synchronization angle is determined with using the developed non-iterative procedure. Then, the distance to fault is calculated. It is applied for calculating the actual values of impedance for the line sections. Performance of such two steps allows investigating the operation of the relays under resistive fault cases. The described post-fault analysis algorithm has been tested with the fault data obtained from versatile ATP-EMTP simulations. The sample examples are reported and discussed