Setting Guidelines - ABB RES670 Applications Manual

1MRK 511 407-UEN C
8.7.3
Phasor measurement unit RES670 2.2 IEC
Application manual
that the turbine runner moves axially and touches stationary parts. They are not
always strong enough to withstand the associated stresses.
Ice and snow may block the intake when the outdoor temperature falls far below
zero. Branches and leaves may also block the trash gates. A complete blockage of
the intake may cause cavitations. The risk for damages to hydro turbines can justify
reverse power protection in unattended plants.
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 68 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-US
Figure 68: 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, UBase and SBase as applicable.
Overpower IED
Q
Operate
Line
Margin
Operating point
without
turbine torque
IEC06000315-2-en.vsd
Section 8
Current protection
P
SEMOD172150-4 v7
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