The slip frequency is
0.0 Hz
. There is a risk that there will be no movement, and thus no synchronisation.
Speed up for slip frequency under 0.3 Hz
If the slip frequency is under 0.3 Hz, the controller automatically speeds up the synchronisation rotation until the phase angle
difference is 30 degrees. This cannot be configured or disabled.
Dynamic synchronisation principle
The dynamic synchronisation principle is shown in the following example.
Figure 5.1
Dynamic synchronisation principle, with vector diagrams
Synchronised
L1
L2
L3
L1
L2
L3
L1
L2
L3
L1
L2
L3
Connected genset
Synchronising genset
L1
L2
L3
L1
L2
L3
L1
L2
L3
L1
L2
L3
2.5
7.5
5.0
0
Time [s]
180
90
0
L1
(genset
)
-
L1
(busbar
) [
°]
270
1503 RPM
50.1 Hz
GB
GB
1500 RPM
50.0 Hz
G
G
Rotation (relative)
Rotation (relative)
The two power sources are the three-phase electricity from the generator and the three-phase electricity at the busbar.
Synchronisation minimises the phase angle difference between the power sources.
In this example, the synchronising genset is running at 1503 RPM (about 50.1 Hz). The online genset is running at 1500 RPM
(about 50.0 Hz). This gives the synchronising genset a positive slip frequency of 50.1 Hz - 50.0 Hz = 0.1 Hz. If the slip frequency is
less than
Delta frequency max.
, and more than
Delta frequency min.
, then the controller can close the breaker when the power
sources are synchronised.
In the example above, the difference in the phase angle between the synchronising genset and the busbar gets smaller and smaller.
When difference in the phase angle is near zero, the controller will send the breaker close signal based on the
Breaker closing time
(this is not shown in the example). In this way, the breaker physically closes when the genset is exactly synchronised with the
busbar.
When the generator is running with a positive slip frequency of 0.1 Hz relative to the busbar, the two systems will be synchronised
every 10 seconds:
DESIGNER'S HANDBOOK 4189340911K UK
Page 154 of 521
