GE L30 Instruction Manual page 198

5.4 SYSTEM SETUP
A B C
Figure 5–14: 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 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
ZERO SEQ CAPACITIVE REACTANCE
1. Three-reactor arrangement: three identical line reactors (X
5
2. Four-reactor arrangement: three identical line reactors (X
connected between reactor-bank neutral and the ground.
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 line ends, the
react
value of the inductive reactance is divided by 2 (or 3 for a three-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.
2.
X = the total neutral reactor inductive reactance. If identical reactors are installed at both line ends, the
react_n
value of the inductive reactance is divided by 2 (or 3 for a three-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.
2.
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-
NOTE
tion error.
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
5-62
Possible 3-Reactor
Line Capacitive Reactance
arrangement
Xreact
X1line_capac
X0line_capac
settings should be calculated as follows:
⋅
X X
1line_capac react
X
= ------------------------------------------------
C1
X X
–
react 1line_capac
⋅
X X
1line_capac react
X
= ------------------------------------------------
C1
X – X
react 1line_capac
For 2 terminal line: X =
react
For 3 terminal line: X =
react
For 2 terminal line: X
react_n
For 3 terminal line: X
react_n
actual values menu. This effect is very dependent on CT and VT accuracy.
L30 Line Current Differential System
Possible 4-Reactor
arrangement
) solidly connected phase to ground:
react
⋅
X X
0line_capac react
, X
= ------------------------------------------------
C0
X X
–
react 0line_capac
) wye-connected with the fourth reactor (X
react
⋅ (
X X
0line_capac react
, X
= -------------------------------------------------------------------------------- -
C0
X + X 3 –
react react_n
⎛
1 1
⁄
1 ---------------------------------- - + ---------------------------------- -
⎝
X X
react_terminal1 react_terminal2
⎛
1 1
⁄
1 ---------------------------------- - + ---------------------------------- -
⎝
X X
react_terminal1 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 SETTINGS
A B C
Xreact
Xreact_n
831731A3.CDR
POS SEQ CAPACITIVE REACTANCE
)
+ X 3
react_n
X
0line_capac
⎞
⎠
⎞
1
+ ---------------------------------- -
⎠
X
react_terminal3
⎞
1
⎠
⎞
1 1
+ --------------------------------------- -
⎠
X
react_n_terminal3
is "Enabled" and the
and
(EQ 5.7)
)
react_n
(EQ 5.8)
METERING
GE Multilin