MiCOM P921/P922/P923 - Schneider - error

P92x/EN FT/H42Page 30/70Technical GuideUser GuideMiCOM P921/P922/P9232.4 MeasurementsAll measured quantities are displayed in primary values (true RMS values, up to the10 th harmonic). They are refreshed once per second.2.4.1 ConfigurationAccording to the connection scheme, which is selected, the phase or line voltages willbe measured and then displayed.2.4.1.1 "3Vpn" configuration (3VTs "Phase-Neutral")The 3 phase voltages VA, VB and VC will be measured by the MiCOM relay.The derived quantities are the symetrical components of the voltage: zero-sequencevoltage (V0), positive and negative sequences voltages (V1 and V2 for MiCOM P922and P923).V 1= 1/ 3(VA + aVB + a²VC)with a = e j2π/3V 2 = 1/ 3(VA + a²VB + aVC)V 0 = 1/ 3(VA + VB + VC)If the protection mode is “Phase-Phase”, the line voltages Vab, Vbc and Vca will beused in the protection algorithms. These line voltages are derived from the formulasbelow:VAB = (VB − VA)VBC = (VC − VB)VCA= (VA − VC)2.4.1.2 "3Vpp+Vr" configuration (3 "Phase-Phase" VTs + 1 residual VT)The 3 line voltages Vab, Vbc, Vca and the residual voltage Vr are then measured bythe MiCOM relay.The derived quantities are: positive and negative sequences voltages (V1 and V2,only for MiCOM P922 and P923):(a − 1)V1 = −1/ 3(UAB + VBC)with a = e j2π/3(1 + 2a)(2 + a)V2 = −1/ 3(UAB + VBC)(1 + 2a)The only protection mode, which is available in this configuration, is the "Phase-Phase" mode.