Research On The Transmission Of Pilot Protection By Using Optic Cable Self-Healing Rings

Relay protection plays the increasingly important role of safety and reliability in the electric power system. Pilot protections are widely used as main protection on the transmission lines of 220KV and 500KV. Protection equipments not only include departments of measurement, gathering and control but also need to send protection information correctly and quickly in order to cut off the faults in a short time. The characteristics of optic cable can meet the expectation because of its structure. Optic cables are used to transmit transmission lines pilot protection information as main protection in recent years. But the original methods of using private optic cable are waste of resources. As the quick development of electric power communications SDH self-healing networks are used widely in the electric power system. SDH is a short way of saying"Synchronous Digital Hierarchy". SDH can multiplex many services such as telephone, data, fax, voice and so on. It has international standards, standard optic interface and powerful network management. It has the function of self-healing when the transmission channels are interrupted. So we think if we can use SDH self-healing networks of electric power private communication to send and receive pilot protection information such as directional comparison pilot protection and current differential pilot protection. If success, we can save more resources at one time it has titanic application values. We select two substations in the city of Suzhou. They are Jinshan substation and Shishan substation. The reason we selected was that the two substations are located in different SDH self-healing rings. We can adjust easily. We study the characteristics of SDH and analyze the transmission structures of protection. After many experiments, we draw important conclusions. One of them is that only multiplex section Switched Ring of SDH can meet the requirement of current differential pilot protection. After we tested the time delay of channels of all kinds of pilot protection we use SDH self-healing ring to transmit pilot protection. We simulated many faults of transmission lines and SDH self-healing ring. The results indicate that protection equipments acted correctly and run well. So far the SDH self-healing ring transmits the information of pilot protection well between Jinshan substation and Shishan substation correctly, quickly and reliably.