GE Multilin B30 Bus Differential System 6-116 ACTUAL VALUES 6.3 METERING66.3METERING 6.3.1 METERING CONVENTIONSa) UR CONVENTION FOR MEASURING PHASE ANGLESAll phasors calculated by UR-series relays and used for protection, control and metering functions are rotating phasors thatmaintain the correct phase angle relationships with each other at all times.For display and oscillography purposes, all phasor angles in a given relay are referred to an AC input channel pre-selectedby the SETTINGS SYSTEM SETUP POWER SYSTEM FREQUENCY AND PHASE REFERENCE setting. This settingdefines a particular AC signal source to be used as the reference.The relay will first determine if any “Phase VT” bank is indicated in the source. If it is, voltage channel VA of that bank isused as the angle reference. Otherwise, the relay determines if any “Aux VT” bank is indicated; if it is, the auxiliary voltagechannel of that bank is used as the angle reference. If neither of the two conditions is satisfied, then two more steps of thishierarchical procedure to determine the reference signal include “Phase CT” bank and “Ground CT” bank.If the AC signal pre-selected by the relay upon configuration is not measurable, the phase angles are not referenced. Thephase angles are assigned as positive in the leading direction, and are presented as negative in the lagging direction, tomore closely align with power system metering conventions. This is illustrated below.Figure 6–1: UR PHASE ANGLE MEASUREMENT CONVENTIONb) UR CONVENTION FOR MEASURING SYMMETRICAL COMPONENTSThe UR-series of relays calculate voltage symmetrical components for the power system phase A line-to-neutral voltage,and symmetrical components of the currents for the power system phase A current. Owing to the above definition, phaseangle relations between the symmetrical currents and voltages stay the same irrespective of the connection of instrumenttransformers. This is important for setting directional protection elements that use symmetrical voltages.For display and oscillography purposes the phase angles of symmetrical components are referenced to a common refer-ence as described in the previous sub-section.WYE-CONNECTED INSTRUMENT TRANSFORMERS:The above equations apply to currents as well.• ABC phase rotation: • ACB phase rotation:827845A1.CDRUR phase anglereference0 o-45 o-90 o-135 o-270 o-225 o-180 o-315 opositiveangledirectionV_0 13--- V AG V BG V CG+ + =V_1 13--- V AG aV BG a2V CG+ + =V_2 13--- V AG a2V BG aV CG+ + =V_0 13--- V AG V BG V CG+ + =V_1 13--- V AG a2V BG aV CG+ + =V_2 13--- V AG aV BG a2V CG+ + =
