Feeder protection and control / Feeder protection
15 ABB
Table 26. Low-set earth-fault protection, stage Io> / 51N
Setting range of pick-up current ‘Io>’
External earth measurement : 0.05...2.0 x In in steps 0.001, infinite
Internal earth measurement : 0.5...2.0 x In in steps 0.001, infinite
External earth measurement : ± 5.0% of set value
External earth measurement : ± 10.0% of set value, for set value <
0.05
Internal earth measurement : ± 15.0% of set value
Operate time delay (DMT) ‘t >’
0.04...64 s in steps of 0.01
1.2 x setting of pick-up current “Io >”
External earth measurement : ± 5.0% of set value or ± 30 ms
Internal earth measurement : ± 10.0% of set value or ± 30 ms
IEC 60255-3:
Normal inverse, Very inverse, Extremely inverse, Long-time inverse
ANSI C37.112:
Moderate inverse, Normal Inverse, Very inverse, Extremely inverse
Special curves: RI inverse
Time multiplier setting ‘k’
0.02...1.6, in steps of 0.01
Operation time accuracy
IEC and ANSI characteristics
RI characteristics
IEC and ANSI characteristics
RI characteristics
External earth measurement : class E(5) or ± 30 ms
External earth measurement : class E(7.5) or ± 30 ms
Internal earth measurement : ± 5.0% of set value or ± 30 ms
Internal earth measurement : ± 10.0% of set value or ± 30 ms
IDMT : 0.96 and DT : 0.98
Table 27. High- set earth-fault protection, stage Io>> / 50N
Setting range of pick-up current ‘Io >>’
External earth measurement : 0.05...12.5 x In in steps 0.001, infinite
Internal earth measurement : 0.5...12.5 x In in steps 0.001, infinite
External earth measurement : ± 5.0% of set value
Internal earth measurement : ± 15.0% of set value
Definite time, Instantaneous
Operate time delay (DMT) ‘to >>’
0.04...64 s in steps of 0.01
External earth measurement : ± 5.0% of set value or ± 30 ms
Internal earth measurement : ± 10.0% of set value or ± 30 ms