Toshiba GR200 Series Instruction Manual page 391

VTF features
2.30.1
The VTF function has three relay elements in order to decide the failure in the VT; hence two
criterions (i.e., for VTF1 and VTF2) exist to detect the failure in the VT.
Phase-to-earth under voltage element (UVVTF)
(i)
For the VTF1 function, the under-voltage element (UVVTF) monitors the under voltage. The
threshold of the UVVTF relay is set using the [UVVTF].
Earth fault overcurrent element (EFVTF)
(ii)
For the VTF2 function, the earth fault overcurrent element (EFVTF) monitors the overcurrent
in zero-sequence. The threshold of the EFVTF relay is set using the [EFVTF].
Earth fault overvoltage element (OVGVTF)
(iii)
For the VTF2 function, the earth fault overvoltage element (OVGVTF) monitors the over
voltage in zero-sequence. The threshold of the OVGVTF relay is set the using [OVGVTF].
Detection criterion for the VTF1
(iv)
The criterion for the VTF1 function is defined when the UVVTF relay operates whereas the
OCD relay does not operate.
Detection criterion for the VTF2
(v)
The criterion for the VTF2 function is defined when both the EFVTF relay and the OCD relay
are not operated whereas the OVGVTF relay is operated.
Operation for the VTF function
2.30.2
When the VTF function detects the failure, issuing the VTF1_DETECT signal is continuing
regardless of the operation of the OCD relay, provided On is set for both the [VTF1EN] and the
[VTF2EN]. Issuing the VTF2_DETECT signal is also continuing regardless of the operation of
both the OCD and the EFVTF relays. Note that issuing the VTF_DETECT signal is cleared
when the operations of the UVVTF relay and the OVGVTF relay are reset.
However, nonetheless the OCD/EFVTF relay is still running after the VTF detection,
issuing the VTF_DETECT signal is cleared, provided OPT-On is set for the settings [VTF1-EN]
and the [VTF2EN].
When issuing the VTF_DETECT signal continues longer than ten seconds, the signal
VTF_DETCT clears to generate the VTF_ALARM signal.
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6F2S1914 (0.49)
GRL200 (Soft 033 & 037)