25% of the rated power to motor it. An engine that is good run in might need no more
than 5%. It is necessary to obtain information from the engine manufacturer and to
measure the reverse power during commissioning.
Gas turbines usually do not require reverse power protection.
Figure 102 illustrates the reverse power protection with underpower protection and
with overpower protection. The underpower protection gives a higher margin and
should provide better dependability
. On the other hand, the risk for unwanted operation
immediately after synchronization may be higher. One should set the underpower
protection (reference angle set to 0) to trip if the active power from the generator is less
than about 2%. One should set the overpower protection (reference angle set to 180) to
trip if the power flow from the network to the generator is higher than 1%.
Underpower protection
Overpower protection
Q Q
P P
Operating point
without
turbine torque
Margin Margin
Operate
Line
Operate
Line
Operating point
without
turbine torque
IEC09000019-2-en.vsd
IEC09000019 V2 EN-US
Figure 102: Reverse power protection with underpower or overpower protection
7.8.3 Setting guidelines
SEMOD172134-4 v7
GlobalBaseSel: Selects the global base value group used by the function to define
IBase, VBase and SBase as applicable.
Operation: With the parameter Operation the function can be set Enabled/Disabled.
Mode: The voltage and current used for the power measurement. The setting
possibilities are shown in table
33.
Section 7 1MRK 505 370-UUS A
Current protection
224 Busbar protection REB670 2.2 ANSI
Application manual
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