Medium voltage switchgear application guide

Medium voltage switchgear application guide
4 - GENERATOR 4 - 1 Switchgear to be used
The control device usually used for operating and protecting
generators is a circuit breaker.
The ■low two power most station current generator uses for the protection generator circuit breaker are:
In (generator/transformer practical cases, power set). station A VHV generators circuit breaker are built is used as self-contained to operate and units
■protection them.
circuits in the of event auxiliary of a generators distribution providing network failure. a power supply to priority
In Its this characteristics case, the circuit are those breaker described used in as chapter a transformer 1 (transformer). protection incomer.
power station generator
G
generator
distributor power supply
power
generator
G
essential
power supply
MV circuit breaker
LV
transformer
MV
MV capacitors
MV
transformer
VHV
VHV circuit breaker
VHV network
4 - 2 Device characteristics
date
11/94
- B•3•2 -
revised
05/2004
When in use, the generator circuit breaker comes up against very
different operating conditions. It must:
■ withstand high load currents (overheating),
■ break strong and highly asymmetrical fault currents which may
be higher than 100% (generator terminal fault),
■ close on very high currents generated by the asymmetry,
■ withstand transient recovery voltage with highly increasing speeds,
■ withstand phase displacement.
DIFFERENT IN OPERATION, CONDITIONS THE GENERATOR OF RUNNING. CIRCUIT IT MUST BREAKER BE ABLE MEETS TO: VERY
■
The
WITHSTAND
rated current
HIGH
is given
LOAD
by
CURRENTS
the following equation: I ≥
3 S
• U
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