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

ABB Switzerland Ltd
3.5.11.1.

Definite time stator earth fault (95 %)

Settings:
Voltage
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).
Voltage Transformer
Fig. 3.5.11.2
3-122
A
Generator
Stator E/F protection for a generator/transformer
unit
REG 316*4 1MRB520049-Uen / Rev. F
V-Setting
Delay
U> 5% U
max
HEST 905 029 C