ABB REG650 Technical Manual page 259

1MRK 502 034-UEN -
Technical Manual
IEC07000186 V1 EN
Figure 129: Simplified Start and Trip logical diagram of the STEFPHIZ protection
There are two different cases of generator block configuration; with or without
generator circuit breaker. If there is no generator breaker the capacitive coupling to
earth is the same under all operating conditions. When there is a generator breaker,
the capacitive coupling to earth differs between the operating conditions when the
generator is running with the generator breaker open (before synchronization) and
with the circuit breaker closed. This can be shown as in figure 130.
- DU
- U +
3N
IEC07000002 V2 EN
Figure 130: Generator block with generator circuit breaker
With the circuit breaker open, the total capacitance will be smaller compared to
normal operating conditions. This means that the neutral point 3
voltage will be reduced compared to the normal operating condition. Therefore,
- U
3
+
3
Section 8
Voltage protection
+
+
Ctr/3
U
3T,L1
-
+
Ctr/3
U
3T,L2
-
+
Ctr/3
U
3T,L3
-
en07000002-2.vsd
rd
harmonic
253