Toshiba GR200 Series Instruction Manual page 71

Charging-current compensation (DIFGL-Ic)
2.3.4
Setting for the compensation
(i)
When the DIFGL function is applied for the protection of underground cables or long overhead
transmission lines, charging-current should be taken account. In other word, the DIFGL
function is influenced by the line capacitance. The user may see charging-current as an
erroneous differential-current†. Therefore, the user should set the values of "line charging
current" and "line voltage" using settings [DIFGL-IcC] and [DIFGL-Vn] when the charging
current compensation function is used in the DIFGL function. The setting values are used to
calculate the line capacitance. The setting values are divided by two when there are two relays
in the system, whereas the setting values are divided by three when there are three relays in
the system.
If line-voltage is not absent, charging-current is shared continuously per-sample-by-
sample basis. The equation is denoted as follows:
where,
Ic = line charging current
C = line capacitance calculated using settings [DIFGL-IcC] and [DIFGL-Vn]
V = line voltage measured
After that, the line current compensated for the charging-current is calculated per-
sample-by-sample basis:
where,
I = compensated current
I' = actual measured current
All necessary phase information has to be taken account basically. This is because the
DIFL function calculates both the charging current and the compensated line current per
sample-by-sample basis.
Activation switch
(ii)
The user should set On for scheme switch [DIFGL-IcC.EN] for the DIFGL-Ic operation.
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Ic = C
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'
I = I − Ic
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6F2S1914 (0.49)
(2.3-9)
(2.3-10)
GRL200 (Soft 033 & 037)