CHAPTER 5: SETTINGS
GROUPED ELEMENTS
L60 LINE PHASE COMPARISON SYSTEM – INSTRUCTION MANUAL
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5
This setting is forced to “Disabled” if a phase VT bank is not assigned at either source 3 or source 4.
The figure shows possible configurations.
Figure 5-105: Charging current compensation configurations
CHARGE COMPENST BLOCK
— This setting selects an input to block charging current compensation. This input is typically the
VT fuse fail element of the source, where the three-phase VT is configured with this setting to block compensation.
Blocking charging current compensation at one end of the line does not block charging current compensation on the other
end. However, even with compensation operating at one end, half (or one-third) of the charging current is still removed
from the net phase comparison current. Alternatively, switch to another setting group with more conservative phase
comparison settings during a VT fuse fail condition.
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 reactance values are
entered in primary kilo-ohms for the total line length.
If shunt reactors are also installed on the line, the resulting value entered in the
POS SEQ CAPACITIVE REACTANCE
and
ZERO
SEQ CAPACITIVE REACTANCE
settings are calculated as follows:
1.
No shunt reactors on the line or reactor current is subtracted from the line current, forcing the L60 to measure the
uncompensated by shunt reactors load/fault current plus the full charging current.
Eq. 5-8
2.
Three-reactor arrangement
— Three identical line reactors (X
react
) solidly connected phase to ground.
Eq. 5-9
3.
Four-reactor arrangement
— Three identical line reactors (X
react
) wye-connected with the fourth reactor (X
react_n
)
connected between reactor-bank neutral and the ground.
Eq. 5-10
X
1line_capac
= the total line positive-sequence capacitive reactance
X
0line_capac
= the total line zero-sequence capacitive reactance
X
react
=the total reactor inductive reactance per phase. If identical reactors are installed at both ends of the line, the
inductive reactance is divided by 2 (or 3 for a three-terminal line) before inserting in the above equations. If the
reactors installed at both ends of the line are different, the following equations apply:
3.1.
For a two-terminal line
