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Application Notes P746/EN AP/G31
MiCOM P746 (AP) 6-
45
AP
8.4 General Substation information
Only a few system parameters are required and it is vital that these are included.
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Number of feeders, bus couplers, bus sections
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Positions of bus sections
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Positions of switchgear plant i.e. circuit breakers, isolators
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Positions of CTs (including the polarity (P1/P2 – S1/S2))
•
Planned future extensions with circuit breaker, isolator and current transformer (CT)
•
Type of electrical network earthing (Solid or impedance)
8.5 Short Circuit Levels
Maximum external fault current (phase to phase and phase to ground faults)
•
Solid:
- Minimum two phase busbar fault current
- Minimum load current on the smallest feeder
- Maximum load current on the biggest feeder or coupler
- Optional: Maximum three phase busbar fault current
•
With impedance:
- Minimum two phase busbar fault current
- Minimum single phase to earth busbar fault current
- Minimum load current on the smallest feeder
- Maximum load current on the biggest feeder
- Optional: Maximum three phase busbar fault current
Maximum substation short-circuit withstand time
8.6 Switchgear
•
Nominal CT ratio
8.7 Substation Architecture
Due to the flexibility of the differential busbar protection there is a number of busbar
configurations that can be accommodated via the topology. Each may have very different
architecture and, therefore, vary in complexity.
You will find in the following pages topology examples of layouts most frequently
encountered. For each example, the number of P746 necessary to protect the busbars is
specified.
Generally, the elements of the protection architecture will be identified in a similar manner to
the principal parts of the substation e.g. by the letters A and B.