Setting Guidelines - ABB REB670 Applications Manual

1MRK 505 337-UUS -
7.9.3
Application manual
A hydro turbine that rotates in water with closed wicket gates will draw electric power
from the rest of the power system. This power will be about 10% of the rated power. If
there is only air in the hydro turbine, the power demand will fall to about 3%.
Diesel engines should have reverse power protection. The generator will take about 15%
of its rated power or more from the system. A stiff engine may require perhaps 25% of the
rated power to motor it. An engine that is well 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 95 illustrates the reverse power protection with underpower IED and with
overpower IED. The underpower IED 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 IED to trip if the active
power from the generator is less than about 2%. One should set the overpower IED to trip
if the power flow from the network to the generator is higher than 1%.
Underpower IED
Q
Operate
Line
Margin
P
Operating point
without
turbine torque
IEC06000315 V2 EN
Figure 95: Reverse power protection with underpower IED and overpower IED

Setting guidelines

GlobalBaseSel: Selects the global base value group used by the function to define (IBase),
(VBase) and (SBase).
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 34.
Overpower IED
Q
Operate
Line
Margin
Operating point
without
turbine torque
IEC06000315-2-en.vsd
Current protection
P
Section 7
217