Siemens SIPROTEC 7UT613 series Manual page 247

Pickup Value
7UT613/63x Manual
C53000-G1176-C160-2
In case of a reverse power, the turbine set must be disconnected from the system as
the turbine operation is not permissible without a certain minimum steam throughout
(cooling effect). In case of a gas turbine set, the motor load can also become too heavy
for the network.
In case of a turbine generator unit the level of the active power input is mainly deter-
mined by the friction losses to be overcome and lies within the following ranges:
Steam turbines:
Gas turbines:
Diesel drives:
It is recommended, however, to measure the reverse power of the turbine generator
unit with the protection yourself during primary test (section "Commissioning", "Verifi-
cation of the Voltage Connections"). As setting value, use approx. half the measured
motoring power. The feature to correct angle faults of the current and voltage trans-
formers should be used especially for very large machines with a particularly low mo-
toring energy (see sections 2.1.4 and "Commissioning", "Verification of the Voltage
Connections and Directional Check").
If the reverse power protection has been assigned to one side of the machine to be
protected, the pickup value of the reverse power can be set as relative value (relevant
to machine rated power) under address 5012 Pr pick-up. As the reverse power is
a negative active power, it is set as a negative value (a positive setting value cannot
be set).
However, if the reverse power protection must be set in ampere (secondary) during
operation, the reverse power must be recalculated as a secondary value and set
under address 5011 P> REVERSE. This is the case if the reverse power protection
has been assigned to a measuring location and not to a side of the main protected
object, thus usually in system applications. The following applies:
with
P secondary power
sec
U primary rated voltage of the voltage transformer (interlinked)
Nprim
U secondary nominal voltage of the voltage transformers
Nsec
(phase-to-phase)
I primary rated current of the current transformer
Nprim
I secondary rated current of the current transformer
Nsec
P primary power
prim
If the primary power is referred to the rated power of the main protected object, it
needs to be converted:
with
≈ 1 % to 3 %
P /S
Revere N
≈ 3 % to 5 %
P /S
Reverse N
P /S > 5 %
Reverse N
2.12 Reverse Power Protection
247