3.1. Regulation and control of distribution points
Control and measuring of electrical switchgears is realized in two levels – process and operator level.
The process level is realized with help of one or more Programmable Logic Controllers (PLC, SPS), which receive and process the measured values and all available information about the position of circuit breakers, disconnecting switches, earthing switches, condition of transformers etc.
PLC programs include the interlocking and interface conditions and ensure the correct manipulation with switchgear equipment. During creation of programs, we take into account the operating manuals of switchgear manufacturer, switchgear configuration, and requirements of the operator. The control system provides evaluation, visualization, and recording of position indication faults, position and control command discrepancies, overflow of analogue value limits.
Configuration of PLC at the process level may be centralized, or (in case of extensive electrical systems) decentralized.
Two-way communication between the process and operator level is ensured through suitable communication protocol. The measured values are being transmitted in one direction, commands of the operator in the reverse direction. The connection link may be provided with help of metallic or optical cable.
The operator level is realized with respect to the required comfort of control - with help of a PC and color monitor, or with help of a console without rotating drive, equipped with a flat LCD display. The complete electrical equipment is divided and displayed on several screen pictures, for example a common overview diagram of switchgear 110 kV, 6 kV and 0.4 kV, individual overview diagrams of switchgear at different voltage levels, and individual control pictures of respective circuit breakers, disconnectors, earthing switches etc. Division of pictures and the color and shape design is always consulted with the operator.
The PLC or the operator station can also communicate with different types of multifunction measuring, control, and protective instruments.
