T
sync
= 1 / (f
sync genset
- f
online genset
) = 1 / (50.1 Hz - 50.0 Hz) = 10 s
INFO
The phases for both three-phase systems rotate. However, in this example, the vectors for the busbar are shown as
stationary to simplify the explanation. This is because we are only interested in the phase angle difference to calculate
when to send the Breakers > [Breaker] > Control > [*B] Close signal.
Load distribution after synchronisation
When the breaker closes, the synchronising genset will take some of the load if it has a positive slip frequency. A negative slip
frequency may lead to reverse power in the synchronising genset.
INFO
The proportion of the load that the synchronising genset takes depends on the frequency difference, and the prime mover
characteristics.
The following example shows that at a given positive slip frequency, the synchronising genset will export power to the load after the
breaker closes.
Figure 5.2
Example of load distribution after synchronisation with a positive slip frequency
G G
Connected genset Synchronising genset
Power
GBGB
Power
0 % 100 %
Fuel injection
0 % 100 %
Fuel injection
The following example shows that at a given negative slip frequency, the synchronising genset will receive power from the
connected genset when the breaker closes. This can cause a reverse power trip.
Figure 5.3
Example of load distribution after synchronisation with a negative slip frequency
G
G
0 % 100 %
Connected genset
Synchronising genset
Power
GB
GB
Power
0 % 100 %
Fuel injection
Fuel injection
DESIGNER'S HANDBOOK 4189340911K UK Page 155 of 521
To Next Page
Loading...
