CAUTION
If the generator is underexcited, there is the risk of an out-of-step condition!
Non-observance of the following measures can result in minor personal injury or material damage.
²
The following measures prevent the risk of an out-of-step condition.
²
Regulate the driving power to 0 by closing the control valves. The generator draws its reverse power from
the electrical power system.
²
Change the excitation until the reactive power Q = 0. As a control measurement, read the active power P
0
and the reactive power Q
0
with the sign, and enter the values in Table 11-1.
²
Increase the excitation slowly until reaching approx. 30 % of the rated apparent power of the generator
(overexcited).
Read the reverse power P
1
with the sign (negative) and the reactive power Q
1
with the sign (positive) in
the functional measured values and note these 2 values in the values table.
²
Reduce the excitation slowly until reaching approx. 30 % of the rated apparent power of the generator
(underexcited).
Read the reverse power P
2
with the sign (negative) and the reactive power Q
2
with the sign (negative) in
the functional measured values and note these 2 values in the values table.
²
Run the generator again at no-load excitation and select the desired operating state.
²
With the measured value pairs (P
1
, Q
1
and P
2
, Q
2
), calculate the correction angle ϕ
corr
with the following
formula:
[fo_RPP correction angle, 2, en_US]
NOTE
Insert the power values with the signs that you read previously!
²
Enter this angle φ
corr
with the same sign as the new correction angle (parameter (_:2311:101) Angle
correction ):
Setting value (_:2311:101) Angle correction = φ
corr
²
You can determine the pickup value of the reverse-power protection from the measured values P1 and
P2.
Use the following formula: P
pickup
= (P
1
+P
2
)/4
Set the value as pickup value: Parameter (_:991:3) Threshold = Ppickup
Check of the Reverse-Power Protection
With a generator that is connected to the power system, the reverse power results from closing the control
valves or from closing the quick stop.
²
In both cases, check the consumed active power (reverse power). The valves could be leaking.
²
Repeat the reverse-power measurement to confirm that the settings are correct.
Functional Tests
11.14 Reverse-Power Protection
SIPROTEC 5, Overcurrent Protection, Manual 1397
C53000-G5040-C017-8, Edition 07.2017
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