CHAPTER 6: PROTECTION SETPOINTS POWER ELEMENTS
850 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL 6–127
Directional Power (32)
The 850 relay provides two identical Directional Power elements per protection group; a
total of 12 elements.
The Directional Power element responds to three-phase directional power and is designed
for reverse power (32REV) and low forward power (32FWD) applications for synchronous
machines or interconnections involving co-generation. The relay measures the three-
phase power from either a full set of wye-connected VTs or a full-set of delta-connected
VTs. In the latter case, the two-wattmeter method is used.
The element has an adjustable characteristic angle and minimum operating power as
shown in the Directional Power characteristic diagram. The element responds to the
following condition:
Where:
P and Q are active and reactive powers as measured per the metering convention
Ɵ is a sum of the element characteristic (DIR POWER 1 RCA) and calibration (DIR
POWER 1 CALIBRATION) angles
SMIN is the minimum operating power.
The element has two independent (as to the Pickup and Delay settings) stages for Alarm
and Trip, and they can be set separately to provide mixed power protection.
Figure 6-55: Directional Power characteristic
By making the characteristic angle adjustable and providing for both negative and positive
values of the minimum operating power, a variety of operating characteristics can be
achieved as presented in the figure below. For example, section (a) in the figure below
shows settings for reverse power, while section (b) shows settings for low forward power
applications.
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