Toshiba GR200 Series Instruction Manual page 83

When the IED_G has a VCT12B†for secondary currents from the CT1 G and the CT2 G ,
in the DIFL function a restraining current (Ir) may be obtained sufficiently by summing the
secondary currents in scalar. In the IED_G the Ir can be generated sufficiently compared with
the Id that may be measured erroneously due to the non-identical CT1 and CT2 characteristics;
thus the DIFL function does not operate. Conversely, in the IED_H, the Ir may not be generated
sufficiently; accordingly, in the IED_H the DIFL function may operate erroneously in response
to the close-in fault.
The through-fault-current countermeasure (TFC) is designed not to issue a trip signal
until the DIFL functions in the IED_G and the IED_H operate simultaneously. The TFC can
operate in the DIFL function when On is set for scheme switch [DIFL-TFC-EN]. The user can
use the TFC in the DIFGL function when scheme switch [DIFGL-TFC-EN] On, as well. Note
that the issuing the trip signal is delayed due to the communication propagation.
†Note: The VCT12B is designed to obtain a pair of three-phase currents. For more
information, see Chapter
analogue input (VCT)
Operation of TFC countermeasure in DIFL
(i)
For the operation of the TFC function, the local DIFL function (i.e., at terminal-G) should
obtain the DIFL operating information at the opposite-terminal (i.e., at terminal-H). Thus, the
DIFL function is required to receive the signal from the opposite-terminal for the TFC function.
The user can use the TFC function when On is set for scheme switch [DIFL-TFC-EN].
During the TFC operation, issuing a trip signal is only carried out when the local DIFL element
and the remote DIFL element operate at the same time. If the TFC function is not required,
the user should set Non for the scheme switch.
Sending DIFL operation signal for the opposite
The signals of the DIFL elements at the both-terminals are exchanged mutually. Figure 2.6-2
shows the DIFL elements; the operated signals (DIFL-A, DIFL-B, and DIFL-C) are sent for
the opposite terminal by the communication.
Technical description: Transformer module for AC
.
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6F2S1914 (0.49)
GRL200 (Soft 033 & 037)