Benefits of a coordinated control and protection concept for medium voltage substations and its realization

Starting from structural, functional, space and cost requirements specific for medium voltage substations, it was possible to realize a microprocessor based substation control system. This system coordinates control and protection, gives easy access to all system data, and therefore improves the operation and maintenance of the substation and of the power network. Cabling, space and installation time have been drastically reduced compared to conventional systems because the bay units on the 16 kV side are built directly into the switchgear cubicles, and no separate RTU is necessary. The system has demonstrated operational advantages in two cases: the protection units keep maximum current and percentage of time delay on each start condition; and locating earth faults on the 16 kV lines by trial and error is supported by allowing the switching off of the auto reclose function on the appropriate line from the network control center, and remotely switching it on again after the fault has been isolated