Toshiba GR-200-5 Instruction Manual page 88

Sensitive earth fault protection (SEF)
If an earth fault occurs, a sensitive earth fault (SEF) function is appropriate in which a fault
current flows very small, in which case there is a distribution system earthed with a high-
impedance. The SEF function is also appropriate for protections such as "standby earth fault"
or "high impedance restricted earth fault in a transformer†". Some directional/non-directional
stages (i.e., SEF1 and other elements) are provided. For simplicity, the SEF1 element is only
discussed, but the characteristic of the other elements are identical to the one of the SEF1
element; hence, the user should understand the expression for the SEF1 as the others unless
a special explanation or instruction has been provided.
†Note: The relay for the restricted earth fault in the transformer can use such quantity
supplied from the core-balanced CT, when Metrosil (Varistors) and setting-
resistors are used externally.
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6F2T0207 (0.01)
GRE200 (5,6)