VAMP 257
Feeder and motor manager
Technical description
VAMP Ltd
108
VAMP 24h support phone : +358 (0)20 753 3264
VM257.EN002
3.4.
Ring network protection
Figure 3.4-1 Feeder terminals VAMP 257 used for protection of ring main
circuit with one feeding point.
Ring networks can be protected with complete selectivity using
directional overcurrent relays as long as there is only one
feeding point in the network. Figure 3.4-1 shows an example of
a ring main with five nodes using one circuit breaker at each
end of each line section (e.g. a ring main unit). When there is a
short-circuit fault in any line section, only the faulty section
will be disconnected. The grading time in this example is 150
ms.
3.5.
Trip circuit supervision
Trip circuit supervision is used to ensure that the wiring from a
protective manager to a circuit-breaker is in order. This circuit
is unused most of the time, but when a feeder manager detects
a fault in the network, it is too late to notice that the circuit-
breaker cannot be tripped because of a broken trip circuitry.
The digital inputs of the manager can be used for trip circuit
monitoring.
3.5.1.
Internal parallel digital inputs
•
The output relays T5, T6, T7 and T8 have internal, parallel
digital inputs available for trip circuit supervision.
•
These inputs are DI29, DI30, DI31 and DI32.
