Toshiba GR200 Series Instruction Manual page 96

DIFL applied to three-terminal line (RDIF and Fault current flowing)
The user can trip a CB remotely when the communication failure occurs. The remote CB is
tripped when the function of remote differential trip is available.
On the other hand, the user should have a special attention for the DIFL settings when
the DIFL function is applied for the line having three-terminals (three-terminal line). This is
because the fault current flows out of the line when a fault occurs internally. Additionally, the
user should have another attention for the occurrence of an external fault on the outgoing line,
because the CT saturation may be induced by the external fault.
Remote different trip
2.7.1
Figure 2.7-1 exemplifies the transmission line and the communication structure on the three-
terminal line. Suppose a fault occurs on the three-terminal line; suppose that the
communication from the terminal-H to the terminal-J is broken down. Then the DIFL function
at the terminal-J cannot issue a trip signal (that is, the terminal-J cannot calculate because of
the absent of remote-current data at terminal-H). However, the terminals G and H can
generate a trip signal because that the DIFL functions at both are able to receive the data from
the terminal-J. In Figure 2.7-1, trip signals should be issued at all terminals as for the fault
occurrence; we know that DIFL functions can calculate in spite of the communication failure.
That is, when the terminal-G starts to provide a trip signal to the terminal-J, the CB at the
terminal-J begins to trip. Remote differential trip function (RDIF) is possible for the above
operation when sub-channels† are provided in the communication. Note that the RDIF
function is just possible to issue a trip signal under the following conditions: (1) a trip signal
being received from a remote terminal, (2) a failure of local-DIFL operation being determined,
(3) communication failure being determined, and (4) settings being completed for the RDIF
operation.
The RDIF function is available for the DIFGL function, as well. In other words, the RDIF
function can operate for both the DIFL and DIFGL functions.
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6F2S1914 (0.49)
GRL200 (Soft 033 & 037)