Toshiba GRL100-701B Instruction Manual page 432

DEFFV, DEFRV > Max. zero sequence voltage (3V o ) in normal conditions
c. IDMT overcurrent element (EFI)
The EFI element should not be operated by the unbalance current present under normal
conditions. It is recommended to set the current after measuring the actual unbalance residual
current for the protected line.
EFI > Max. zero sequence current (3I o ) in normal condition
d. Switch-on-to-fault/stub protection (OCH)
The setting of the OCH element should be lower than the minimum fault current (I fmin ) at the
busbar:
OCH < (I fmin /CT ratio) × 0.5
= {(0.8(margin) × 2.47kA)/(600/5)} × 0.5
= 8.23A
e. Breaker failure protection (BF)
The setting of the BF element should be lower than the minimum fault current:
OCBF < (I fmin /CT ratio) × 0.5
= {(0.5 × 2.47kA)/(600/5)} × 0.5
= 5.14A
Setting of TBF1 = Breaker opening time + OCBF reset time + Margin
= 40ms + 10ms + 20ms
= 70ms
Setting of TBF2 = TBF1 + Output relay operating time + Breaker opening time +
= 70ms + 10ms + 40ms + 10ms + 10ms
= 140ms
Element Setting
DEFFI 2.5 (A)
DEFRI 2.5 (A)
DEFFV 21.0 (V)
DEFRV 21.0 (V)
DEFF θ
85
DEFR θ 85
Element Setting
EFI 2.5 (A)
TEFI 0.5
MEFI S
Element Setting
OCH 8.2 (A)
OCBF reset time + Margin
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