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Fig. 1. Substation O/C and E/F protection using the standard configuration A or B with relevant options. In the incoming feeder bay, the protection functions not used are uncoloured and indicated with a dashed block outline. The relays are equipped with optional arc protection functions, enabling fast and selective arc protection throughout the switchgear.
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Fig. 2. Substation O/C and E/F protection using the standard configuration C or D with relevant options. In the incoming feeder bay the unemployed protection functions are uncoloured and indicated with a dashed block outline. The busbar protection is based on the interlocking principle, where the start of the O/C protection of the outgoing feeder sends a blocking signal to the instantaneous O/C stage of the incoming feeder. In the absence of the blocking signal, the O/C protection of the incoming feeder will clear the internal switchgear (busbar) fault.
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Fig. 3. Protection and control of two incoming feeders using IEDs with standard configuration F. The two incoming feeders can be connected in parallel by closing the busbar-sectionalizing breaker. To achive selective overcurrent protection, directional overcurrent stages are needed. Busbar main and back-up protection for outgoing feeders is implemented using residual overvoltage protection stages. Phase undervoltage and overvoltage protection can be used for tripping or just alarming purposes.