GE T60 Instruction Manual page 481

CHAPTER 5: SETTINGS GROUPED ELEMENTS
The sensitive directional power element responds to three-phase directional power and is designed for reverse power and
low forward power 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. See the UR-series Metering Conventions section in chapter 6 for details
regarding the active and reactive powers used by the sensitive directional power element.
The element has an adjustable characteristic angle and minimum operating power as shown in the Directional Power
Characteristic diagram that follows. The element responds to the following condition:
P cos θ + Q sin θ > SMIN Eq. 5-55
where
P and Q are active and reactive powers as measured per the UR metering convention
θ is a sum of the element characteristic ( ) and calibration ( ) angles
DIR POWER 1 RCA DIR POWER 1 CALIBRATION
SMIN is the minimum operating power
The operating quantity is displayed in the actual value.
ACTUAL VALUES  METERING  SENSITIVE DIRECTIONAL POWER 1(2)
The element has two independent (as to the pickup and delay settings) stages for alarm and trip, respectively.
Figure 5-174: Directional power characteristic
5
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 following figure. For example,
section (a) in the figure shows settings for reverse power, while section (b) shows settings for low forward power
applications.
T60 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL 5-299