ABB REG316 4 Series - Definite Time Stator Earth Fault (95 %)

ABB Switzerland Ltd REG 316*4 1MRB520049-Uen / Rev. F
3-122
3.5.11.1. Definite time stator earth fault (95 %)
Settings:
Voltage V-Setting
Delay Delay
The definite time stator E/F scheme (95%) is designed for the
protection of generators or generator/transformer units.
Description
The standard zone of protection in the case of genera-
tor/transformer units is 95 % of the length of the stator winding
(see Fig. 3.5.11.2). It is normal to limit the zone to 95 % to avoid
any risk of false tripping. The stator E/F function is connected
either to the v.t. at the stator star-point or to the v.t’s at the gen-
erator terminals. In either case, the function monitors the dis-
placement of the star-point caused by a stator E/F. The corre-
sponding off-set voltage becomes a maximum for an E/F at a
generator terminal and zero for an E/F at the star-point (see Fig.
3.5.11.2).
HEST 905 029 C
A
U>
U
Generator
5% U
max
Voltage Transformer
9
5
%
5
%
U
m
a
x
Fig. 3.5.11.2 Stator E/F protection for a generator/transformer
unit