REG 316*4 1MRB520049-Uen / Rev. B ABB Switzerland Ltd
4-35
4.2.5.9. Required REG 316*4 functions
The following REG 316*4 functions are required for a discrimina-
tive ground fault scheme:
· 1 100 V voltage input
· 1 metering current input
· 1 to 4 tripping channels
depending on the number of circuit-breaker tripping coils and
whether redundancy is required or not
· 1 “Ground fault” signalling channel
· 2 signalling inputs.
The start-up scheme requires:
· 1 100 V voltage input
· 1 or 2 tripping channels for the de-excitation switch
· 1 “Start-up ground fault” signalling channel
· 1 “Generator CB closed” signalling input.
4.2.5.10. Protection sensitivity
For a ground fault at the generator terminals, a real power cur-
rent of 20 A results in a voltage of approximately 80 V, respec-
tively 100 V at the input of the REG 316*4. The lower of the two
voltages takes the voltage drops of three single-phase v.t’s into
account. A current of 4 A and a voltage of 16 V are produced by
a ground fault at 20 % of the winding from the start-point. The
current at the input of the REG 316*4 in the case of a core-bal-
ance c.t. with a ratio of 100/1 A is 0.04 A which corresponds to a
power of 0.64 W at 16 V. This is detected by the power function
with a setting of 0.5 % or 0.5 W at U
RN
= 100 V and I
RN
= 1 A.
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