Toshiba GR200 Series Instruction Manual page 34

Autoreclosing CB (ARC) after the operation of the protection functions
1.1.8
Most faults that occur on high voltage or extra-high voltage overhead lines are transient faults
caused by lightning. Once a transient fault occurs, the circuit breaker (CB) is tripped to clear
the fault; reclosing the CB is performed after the confirmation of the de-ionized gases in the
CB. The time between clearing the fault and reclosing the CB should be made as short as
possible to keep the power system stable. Given the de-ionization generated by the fault arc,
we should take enough time for the de-ionization, which commences once the CBs at all
terminals are tripped. However, we can take the time in minimum if all CBs at the terminals
are tripped at the same time.
Conventional applications
1.1.9
[OC] Directional/non-directional phase over current protection
The OC function provides some relay elements. The OC function includes inverse time and
definite time characteristics.
[EF] Directional/Non-directional phase earth fault protection
The EF function provides some relay elements. The choice of characteristic is selectable
between inverse time, and definite time.
[SOTF-OC] Switch on to fault protection
In order to quickly remove a fault which may occur when a faulted line or bus-bar is energized,
the SOTF protection will be operational for a certain period after the circuit breaker closes.
[FS] Fail-safe protection
The IED is provided with Fail-safe elements which function as a check relay and enhance
security against a fault a power system with week infeed, or prevent a false tripping due to a
signal failure in the protection system.
[VTF] VT failure detection function
When a fault occurs in the secondary circuit of a voltage transformer (VT), voltage dependent
measuring elements may operate incorrectly. Thereby when the VTF function detects a failure
in the VT, the VTF function blocks the voltage dependent relay.
[CTF] CT failure detection function
When a fault occurs in the secondary circuit of a current transformer (CT), current dependent
measuring elements may operate incorrectly. Thereby when the CTF function detects a failure
in the CT, the CTF function blocks the current dependent relay.
[FL-AZ] Fault locator with communication
When a fault is detected, such function, which communicates with a far end IED, determines
fault location with data in the IEDs between. Were to the IED to fail to communicate with the
far end IED, another fault locator function, which is cited below, would be used as a substitute
for this function.
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6F2S1914 (0.49)
GRL200 (Soft 033 & 037)