GE L90 Instruction Manual page 131

5 SETTINGS
Possible 3-Reactor
A B C
arrangement
Figure 5–9: CHARGING CURRENT COMPENSATION CONFIGURATIONS
• POSITIVE and ZERO SEQUENCE CAPACITIVE REACTANCE: The values of positive and zero sequence capacitive
reactance 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 compensation
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
ZERO SEQ CAPACITIVE REACTANCE
1. 3-reactor arrangement: three identical line reactors (X
2. 4-reactor arrangement: three identical line reactors (X
nected between reactor-bank neutral and the ground.
X
C1
X = the total line positive sequence capacitive reactance
1line_capac
X = the total line zero sequence capacitive reactance
0line_capac
X = the total reactor inductive reactance per phase. If identical reactors are installed at both ends of the line,
react
the value of the inductive reactance is divided by 2 (or 3 for a 3-terminal line) before using in the above
equations. 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:
X = the total neutral reactor inductive reactance. If identical reactors are installed at both ends of the line,
react_n
the value of the inductive reactance is divided by 2 (or 3 for a 3-terminal line) before using in the above
equations. 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.
NOTE
Differential current is significantly decreased when
proper reactance values are entered. The effect of charging current compensation is viewed in the
!"
NOTE
87L DIFFERENTIAL CURRENT
GE Multilin
Line Capacitive Reactance
Xreact
X1line_capac
X0line_capac
settings should be calculated as follows:
⋅
X X
1line_capac react
X ------------------------------------------------ , X
=
C1
X X
–
react 1line_capac
⋅
X X
1line_capac react
------------------------------------------------ , X
=
C0
X X
–
react 1line_capac

⁄
X 1 ---------------------------------- -
=

react
X
react_terminal1

⁄
X 1 ---------------------------------- -
=

react
X
react_terminal1

⁄
X 1
=

react_n

⁄
X 1
=

react_n
actual values menu. This effect is very dependent on CT and VT accuracy.
L90 Line Differential Relay
Possible 4-Reactor
arrangement
Xreact_n
POS SEQ CAPACITIVE REACTANCE
) solidly connected phase to ground:
react
⋅
X X
0line_capac react
------------------------------------------------
=
C0
X X
–
react 0line_capac
) wye-connected with the fourth reactor (X
react
⋅ (
X X + X 3
0line_capac react react_n
-------------------------------------------------------------------------------- -
=
X + X 3 X
–
react react_n 0line_capac
1 1

---------------------------------- -
+

X
react_terminal2
1 1
---------------------------------- -
+ +
X
react_terminal2
1 1
--------------------------------------- - --------------------------------------- -
+
X X
react_n_terminal1 react_n_terminal2
1 1
--------------------------------------- - ------------------------------------------
+
X X
react_n_terminal1 react__n_terminal2
CHARGING CURRENT COMPENSATION
5.3 SYSTEM SETUP
A B C
Xreact
831731A3.CDR
(EQ 5.6)
) con-
react_n
)
(EQ 5.7)
1

---------------------------------- -

X
react_terminal3


1 
--------------------------------------- -
+

X
react_n_terminal3
is "Enabled" and the
METERING
and
5
5-41