3.3 Commissioning
287
7UM61 Manual
C53000-G1176-C127-3
• Reduce excitation slowly to approximately 30% rated apparent power of generator
(underexcited).
– Read out the motoring power P
2
with polarity (negative) in the operational mea-
sured values and note it (see table below).
– Read out reactive power Q
2
with polarity (negative) in the operational measured
values and note it (see table below).
• Adjust generator to no-load excitation and shut it down or select the desired opera-
tional state.
Figure 3-22 Determination of the Correction Angle W0
The read-out measured values P
1
, and P
2
are now used to carry out CT angle error
correction. First calculate a correction angle from the measured value pairs according
to the following formula:
The power values must be inserted with their correct polarity as read out! Oth-
erwise faulty result!
This angle Ï•
corr
is entered with reversed sign as the new correction angle under
address 204 CT ANGLE W0:
Setting value CT ANGLE W0 = – ϕ
corr
A quarter of the sum of the measured values P
1
+ P
2
is set as pickup value of the
reverse power protection P> REVERSE under address 3102.
Calibrating the
Reverse Power Pro-
tection
If a generator is connected with the network, reverse power can be caused by
• closing of the regulating valves,
• closing of the trip valve
Because of possible leakages in the valves, the reverse power test should – if possible
– be performed for both cases.
In order to confirm the correct settings, repeat the reverse power measurement again.
For this, the reverse power protection (address 3101) is set to Block relay in order
to check its effectiveness (using the indications).
Start up generator and synchronize with network. Close regulating valves.
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