Toshiba GR-200-5 Instruction Manual page 247

CT failure detection (CTF)
If a failure occurs on the secondary circuit in the current transformer (CT), the operation in
relays cannot be obtained properly because the relays do not measure incoming currents
correctly. Therefore, the CT failure detection (CTF) function is provided to block operating the
relays upon occurrence of the CT failure. Accordingly, an alarm signal is issued if a CT failure
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is detected by the CTF function; a detection signal by the CTF function blocks operating the
relay for the current monitor
After the disappearance of the CT failure, the CTF function can take account of the CT
secondary circuit being in healthy condition in the three-phase; the operation of the CTF
function is reset . Thus, the blocked relays are allowed to operate again. Incidentally, issuing
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the CTF alarm is automatically removed and then the user can find resetting the CTF alarm.
Note: The CTF function can block the operation in several relays, but it does not block
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the operation in other relays. To know the blocking, refer sections of the respective
protection functions.
Note: The user can programmable the operation using the setting and the PLC signals.
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6F2T0207 (0.01)
GRE200 (5,6)