4–254 889 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUALPROTECTION CHAPTER 4: SETPOINTSPath: Setpoints > Protection > Group 1(6) > Power > Directional Power 1(X)FUNCTIONRange: Disabled, Trip, Alarm, Latched Alarm, ConfigurableDefault: DisabledRCARange: 0 to 359° in steps of 1°Default: 180°This setting specifies the Relay Characteristic Angle (RCA) for the Directional Powerfunction. Application of this setting is threefold:1. It allows the element to respond to active or reactive power in any direction (activeoverpower/underpower, etc.).2. Together with a precise calibration angle, it allows compensation for any CT and VTangular errors to permit more sensitive settings.3. It allows for required direction in situations when the voltage signal is taken frombehind a delta-wye connected power transformer and phase angle compensation isrequired.For example, the active overpower characteristic is achieved by setting DIR POWER 1RCA to “0°,” reactive overpower by setting DIR POWER 1 RCA to “90°,” active underpowerby setting DIR POWER 1 RCA to “180°,” and reactive underpower by setting DIR POWER 1RCA to “270°”.CALIBRATIONRange: 0 to 0.95° in steps of 0.05°Default: 0°This setting allows the Relay Characteristic Angle to change in steps of 0.05°. This maybe useful when a small difference in VT and CT angular errors is to be compensated topermit more sensitive settings.The setting virtually enables calibration of the Directional Power function in terms of theangular error of applied VTs and CTs. The element responds to the sum of the DIRPOWER 1 RCA and DIR POWER 1 CALIBRATION settings.STAGE 1 SMINRange: -1.200 to 1.200 x Rated Power in steps of 0.001 x Rated PowerDefault: 0.100 x Rated PowerThe setting specifies the minimum power as defined along the relay characteristic angle(RCA) for the stage 1 of the element. The positive values imply a shift towards theoperate region along the RCA line; the negative values imply a shift towards the restrainregion along the RCA line. Refer to the Directional power sample applications figure fordetails. Together with the RCA, this setting enables a wide range of operatingcharacteristics.The setting applies to three-phase power and the rated power is as follows:Rated Power = 3 x VTSecondary (phase-neutral) x VT Ratio x CTPrimary (Wye-connected VT), orRated Power = (3)1/2 x VTSecondary (phase-phase) x VTRatio x CTPrimary (Delta-connected VT)For example:A setting of 2% for a 200 MW machine is 0.02 × 200 MW = 4 MW. If 7.967 kV is a primaryVT phase-neutral voltage and 10 kA is a primary CT current, the source rated power is239 MVA, and, SMIN must be set at 4 MW/239 MVA =0.0167 x Rated ≈ 0.017 x Rated. Ifthe reverse power application is considered, RCA = 180° and SMIN = 0.017 x Rated.The element drops out if the magnitude of the positive-sequence current becomesvirtually zero, that is, it drops below the cutoff level.
