ABB RELION REB500 Technical Manual page 67

1MRK 505 406-UEN B
phase impedance loops are continuously processed in sequence, providing the enabling and
ground fault criteria are fulfilled.
The equations used to calculate the loop impedances are the same as those used in
It is then determined whether the impedance measured lies within the characteristic and
whether it is in the direction of the zone being measured. The overreaching zone and reverse
measuring zone are evaluated as part of the measurement of the first zone. The corresponding
tripping and other signals are processed by the system logic. Tripping of the circuit-breaker,
however, only takes place after a measuring unit has operated twice.
Bay protection functions REB500
Technical manual
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Section 5
Bay protection functions
Section .
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