Integrated protection of distribution lines using transient comparison technique

This paper presents a novel integrated protection scheme for distribution lines based on Transient Polarity Comparison technique. In the proposed scheme, the specially designed interface units are installed at each substation and connected to the CTs on every line associated to the busbar. The unit converts the measured signals to optical format and sends to the central protection relay through a substation communication network, which is interfaced to all the interface units in the substation. A central protection relay receives measured currents from all locations in the substation and extracts the fault generated transient current signals. The super-imposed components containing in the transient signals captured from each relay are then extracted and the polarities of the signals derived. The polarity of the signals is then sent over to other end(s) of the protected line section(s). The comparison of the polarities of the signals from the line ends will determine whether a fault is inside in a protected network. Simulation results presented in the paper confirm the feasibility of the scheme.