ABB RES670 Technical Manual page 267

1MRK 511 408-UUS A
Phasor measurement unit RES670 2.2 ANSI
Technical manual
Often, the motoring condition may imply that the turbine is in a very dangerous state.
The task of the reverse power protection is to protect the turbine and not to protect the
generator itself.
Figure 83 illustrates the low forward power and reverse power protection with
underpower and overpower functions respectively. 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%.
When IED with a metering class input CTs is used pickup can be set to more sensitive
value (e.g.0,5% or even to 0,2%).
Underpower IED
Q
Trip
Line
Margin
Tripping point
without
turbine torque
ANSI06000315 V1 EN-US
Figure 83: Reverse power protection with underpower IED and overpower IED
Overpower IED
Q
Trip
Line
Margin
P
Tripping point
without
turbine torque
ANSI06000315-1-en.vsd
Section 8
Current protection
P
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