5-90 L30 Line Current Differential System GE Multilin5.4 SYSTEM SETUP 5 SETTINGS5Figure 5–20: CHARGING CURRENT COMPENSATION CONFIGURATIONS• POSITIVE and ZERO SEQUENCE CAPACITIVE REACTANCE: The values of positive and zero-sequence capacitivereactance of the protected line are required for charging current compensation calculations. The line capacitive reac-tance values should be entered in primary kohms for the total line length. Details of the charging current compensa-tion algorithm can be found in Chapter 8: Theory of operation.If shunt reactors are also installed on the line, the resulting value entered in the POS SEQ CAPACITIVE REACTANCE andZERO SEQ CAPACITIVE REACTANCE settings should be calculated as follows:1. Three-reactor arrangement: three identical line reactors (Xreact ) solidly connected phase to ground:(EQ 5.7)2. Four-reactor arrangement: three identical line reactors (Xreact) wye-connected with the fourth reactor (Xreact_n)connected between reactor-bank neutral and the ground.(EQ 5.8)X1line_capac = the total line positive-sequence capacitive reactanceX0line_capac = the total line zero-sequence capacitive reactanceXreact = the total reactor inductive reactance per phase. If identical reactors are installed at both line ends, thevalue of the inductive reactance is divided by 2 (or 3 for a three-terminal line) before using in the aboveequations. If the reactors installed at both ends of the line are different, the following equations apply:1. For 2 terminal line:2. For 3 terminal line:Xreact_n = the total neutral reactor inductive reactance. If identical reactors are installed at both line ends, thevalue of the inductive reactance is divided by 2 (or 3 for a three-terminal line) before using in the aboveequations. If the reactors installed at both ends of the line are different, the following equations apply:1. For 2 terminal line:2. For 3 terminal line:Charging current compensation calculations should be performed for an arrangement where the VTs are con-nected to the line side of the circuit; otherwise, opening the breaker at one end of the line will cause a calcula-tion error.Possible 3-Reactorarrangement Line Capacitive ReactanceXreact XreactXreact_nX1line_capacX0line_capacPossible 4-ReactorarrangementA B C A B C831731A3.CDRX C1X1line_capac Xreact⋅Xreact X1line_capac–------------------------------------------------= , X C0X0line_capac Xreact⋅Xreact X0line_capac–------------------------------------------------=X C1X1line_capac Xreact⋅Xreact X1line_capac–------------------------------------------------= , X C0X0line_capac Xreact 3+ Xreact_n( )⋅Xreact 3+ Xreact_n X0line_capac–---------------------------------------------------------------------------------=Xreact 1 1Xreact_terminal1----------------------------------- 1Xreact_terminal2-----------------------------------+ ⁄=Xreact 1 1Xreact_terminal1----------------------------------- 1Xreact_terminal2----------------------------------- 1Xreact_terminal3-----------------------------------+ + ⁄=Xreact_n 1 1Xreact_n_terminal1---------------------------------------- 1Xreact_n_terminal2----------------------------------------+ ⁄=Xreact_n 1 1Xreact_n_terminal1---------------------------------------- 1Xreact__n_terminal2------------------------------------------ 1Xreact_n_terminal3----------------------------------------+ + ⁄=NOTE
