Toshiba GR200 Series Instruction Manual page 58

If the user wishes to reset the DIFL-CTF operation after the breaking wire is removed, the
user should set On for scheme switch [CTFL-EN]. If the user wishes to reset the DIFL-CTF
operation after any operation of the DUV-DIFL relays, the user should set OPT-On for the
scheme switch [CTFL-EN]. On the other hand, if the user wishes not to operate the DIFL-CTF
function, set Off for the scheme switch.
If the failure in the CT circuit lasts for 10sec or longer, signal "DIFL-CTF-ALARM" is
also provided‡. The user can use an external CT circuit-failure function, provided the user
wishes to use the external function in place of the DIFL-CTF function; a PLC connection point
"EXTERNAL-DIFL-CTF" is provided for this purpose.
If the CT circuit-failure detection function is required not to operate, the user can remove
the operation using PLC connection point "DIFL-CTF_BLOCK". The CT circuit-failure
detection function can also be stopped when the AMF-ON signal is injected.
†Note: AMF feature is used for the test. To generate the AMF signal for the test, see
chapter
‡Note: They are transferred to the automatic supervision function, which we shall
discuss separately.
Charging-current compensation (DIFL-Ic)
2.2.4
As illustrated in Figure 2.2-7, when the DIFL function is used for underground cables or long
overhead transmission lines, charging-current flows due to the influence of the line capacitance.
The changing-current may be observed as an erroneous differential current.
Figure 2.2-7 Phenomenon of charging current
The DIFL sensitivity can be compensated using the charging current, but its
compensation can be performed at the expense of reduced sensitivity to internal faults. In
addition, the charging current can vary strongly in response to the running line-voltage. Thus,
the user should take into account it for the setting.
The DIFL function provides a charging current compensation function in order to avoid
the effect of the charging current so that the DIFL sensitivity is maintained. The compensation
User interface: Test sub-menu
Bus G
IED G
- 35 -
.
Bus H
IED H
Ic
6F2S1914 (0.49)
GRL200 (Soft 033 & 037)