ABSTRACT
The output signals generated by the computer-based protection and control system energize the actuating coils of switches and power transformer tap-changers, change the settings of analogue devices, are displayed on the screens of workstations and registered by recording devices and transmitted to remote locations by communications equipment. Digital computers, initially used in electrical power systems for off-line calculations, statistics etc., and then for planning and forecasting, soon found their way into load dispatching centers and on-line applications. A major advantage of digital techniques is their ability to continuously self-monitor important circuits and functions and ensure the uninterrupted availability of the devices. The basic requirements which digital protection and control systems have to fulfil with regard to selectivity, availability, speed etc., are naturally the same as for conventional analogue protection and control devices. The input signals may be analogue, digital or binary states.
