A new generation of control and diagnostic techniques for gas insulated switchgear

New secondary systems on the bay and station levels of high-voltage substations with gas insulated switchgear (GIS) offer the opportunity for an optimisation of reliability, together with a reduction of the life cycle cost, of the GIS. These goals can be reached by decreasing the outage time of the switchgear, by reducing failures in service, by new more effective maintenance strategies and by optimizing the utilization of the switchgear. For all these measures, more information about the status of the switchgear is necessary. Modern secondary equipment capable of providing these information is characterized by a systematic use of serial data bus connections replacing the parallel wiring of conventional GIS bays. A major communication link of this system is the process bus. It connects all installed devices in the bay, e.g. circuit breaker, disconnector/earthing switches, current and voltage transducers etc., with the bay related control and protection devices. Major devices are intelligent modules equipped with their own small computers performing the main monitoring and diagnostic functions independently. The computers acquire the data from a number of sensors, process them and transmit the information onto the data bus system. Vice versa they receive information from the data bus system and activate actuators if necessary. This GIS design offers opportunities to apply new diagnostic technologies which can detect a wide range of physical variables. The control and communication system as well as the diagnostic system are described in detail.