Development of high resolution and high reliability time synchronizing signal distribution technique for substation systems

A high reliability, high resolution synchronizing signal distribution technique suitable for application to the entire substation system has been developed. This technique has already been widely applied in operational systems and protection relays. Results have been excellent to date. A digital signal is transmitted over optical fiber for synchronization with high resolution. A signal encoding technique is used to solve the problem of incorrect timing detection caused by optical device deterioration and therefore high reliability synchronization has been achieved. Commercial GPS receiver and asynchronous communication is used to provide a cost reduced and simplified system. A signal superimposing technique is used to reduce the number of optical fibers. A long-term test was conducted using a GPS receiver and line current differential relay system developed in our factory. No problems were encountered in the availability of the synchronizing signal and no relay faults have occurred. High reliability performance is confirmed and we are convinced that this technique can be applied to all substations in the future.