ABB REG316 4 Series, Operating Instructions Manual

Page: 175 / 980

REG 316*4 1MRB520049-Uen / Rev. F
ABB Switzerland Ltd
3-137
3.5.11.3. Interturn protection
(voltage principle)
Settings:
Overvoltage V-Setting
Delay Delay
The purpose of the interturn protection is to detect short-circuits
between the turns of the generator stator windings.
The scheme should be as sensitive as possible to detect the
majority of interturn faults. However, because of various residual
voltages caused by asymmetries, the setting may not be lower
than 5 % U
N
. A slight delay will prevent false tripping due to
transients.
Both ends of the primaries of v.t’s must be designed for the full
HV potential!
Since the star-points of the generator and the v.t’s are con-
nected, the high short-circuit power of the generator would cause
severe damage in the event of an interturn fault on a v.t. primary.
HV fuses should therefore be inserted in the v.t. primaries.
Typical settings:
V-Setting 0.05 U
N
Delay 0.5 s
HEST 905 017 C
R
S T
Generator
Voltage transformer
U>
Fig. 3.5.11.8 Interturn protection according to the voltage
principle