Toshiba GRL100-701B Instruction Manual page 39

double-circuit lines, lines with outer loop circuit, or double-circuit lines with one-and-a-half
busbar system. DIFI2 should be set larger than the possible largest value of outflow current in
case of an internal fault.
As the occurrence of current outflow depends on the power system configuration or operation, it
is necessary to check whether it is possible for the fault current to flow out of the line. If so, the
factor must be taken into consideration when making the setting.
In other applications, only the first and second factors need be considered.
Setting of DIFGI
The setting of DIFGI is determined from the high-impedance earth fault current.
The setting value of DIFGI must be identical at all terminals. If the terminals have different CT
ratios, then the settings for DIFGI must be selected such that the primary settings are identical.
Setting of DIFSV
When using the differential current monitoring function, the setting of DIFSV is determined
from the maximum erroneous differential current during normal service condition.
K⋅Ierr < DIFSV < DIFI1 / (1.5 to 2)
Ierr: maximum erroneous differential current
For the GRL100 provided with the charging current compensation, the condition related to the
charging current can be neglected.
The setting value of DIFSV must be identical at all terminals. If the terminals have different CT
ratios, then the settings for DIFSV must be selected such that the primary settings are identical.
Setting of DIFIC
The internal charging current under the rated power system voltage is set for DIFIC. The
charging current is measured by energizing the protected line from one terminal and opening the
other terminal.
If the measured power system voltage differs from the rated one, the measured charging current
must be corrected.
The setting value of DIFIC must be identical at all terminals. If the terminals have different CT
ratios, then the settings for DIFIC must be selected such that the primary settings are identical.
Setting of OCCHK
This setting is available for [COMMODE]='GPS-MODE' setting. The OCCHK must be set
larger than any of the following three values, taking the errors due to charging current and
measurement inaccuracy into consideration. If the differential current setting in the small current
region DIFI1 differs between terminals due to different CT ratios, the larger DIFI1 is applied.
• 14 × charging current (A)
• 0.5 × DIFI1 setting (A)
• 0.5A (or 0.1A in case of 1A rating)
Setting of PDTD, [COMMODE], [GPSBAK], [AUTO2B], [TERM], [SRC θ] and [RYIDSV]
The setting of these items must be identical at all terminals.
COMMODE: generally set to 'B-MODE' which is standard operating mode. Set to 'A-MODE'
if the opposite terminal relay is an old version of GRL100, that is GRL100-∗∗∗A,
-∗∗∗N or -∗∗∗Y. If the relay is applied to the GPS-based synchronization, set to
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6 F 2 S 0 8 5 0