5-126 G30 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUALSYSTEM SETUP CHAPTER 5: SETTINGS5Because energy parameters are accumulated, these values should be recorded and then reset immediately prior tochanging VT characteristics.Two banks of phase/auxiliary VTs can be set, where voltage banks are denoted in the following format (X represents themodule slot position letter):Xa, where X = {F, M} and a = {5}See the Introduction to AC Sources section at the beginning of this chapter for details.With VTs installed, the relay can perform voltage measurements as well as power calculations. Enter the PHASE VT F5CONNECTION made to the system as “Wye” or “Delta.” An open-delta source VT connection is entered as “Delta.”5.5.2 Power systemSETTINGS SYSTEM SETUP POWER SYSTEMThe power system NOMINAL FREQUENCY value is used as a default to set the digital sampling rate if the system frequencycannot be measured from available signals. This can happen if the signals are not present or are heavily distorted. Beforereverting to the nominal frequency, the frequency tracking algorithm holds the last valid frequency measurement for asafe period of time while waiting for the signals to reappear or for the distortions to decay.The phase sequence of the power system is required to properly calculate sequence components and power parameters.The PHASE ROTATION setting matches the power system phase sequence and informs the relay of the actual system phasesequence, either ABC or ACB. CT and VT inputs on the relay, labeled as A, B, and C, must be connected to system phases A,B, and C for correct operation. PHASE VT F5SECONDARY: 66.4 VRange: 25.0 to 240.0 V in steps of 0.1 PHASE VT F5RATIO: 1.00 :1Range: 1.00 to 24000.00 in steps of 0.01 AUXILIARY VT F5CONNECTION: VagRange: Vn, Vag, Vbg, Vcg, Vab, Vbc, Vca AUXILIARY VT F5SECONDARY: 66.4 VRange: 25.0 to 240.0 V in steps of 0.1 AUXILIARY VT F5RATIO: 1.00 :1Range: 1.00 to 24000.00 in steps of 0.01The nominal PHASE VT F5 SECONDARY voltage setting is the voltage across the relay input terminals when nominalvoltage is applied to the VT primary.For example, on a system with a 13.8 kV nominal primary voltage and with a 14400:120 volt VT in a deltaconnection, the secondary voltage is 115; that is, (13800 / 14400) × 120. For a wye connection, the voltage valueentered must be the phase to neutral voltage, which is 115 / = 66.4.On a 14.4 kV system with a delta connection and a VT primary to secondary turns ratio of 14400:120, the voltagevalue entered is 120; that is, 14400 / 120. POWER SYSTEM NOMINAL FREQUENCY:60 HzRange: 25 to 60 Hz in steps of 1 PHASE ROTATION:ABCRange: ABC, ACB REVERSE PH ROTATION:OffRange: FlexLogic operand FREQUENCY AND PHASEREFERENCE: SRC 1Range: SRC 1, SRC 2, SRC 3, SRC 4 FREQUENCYTRACKING:EnabledRange: Disabled, Enabled
