ABB REG316 4 Series - Page 306

ABB Switzerland Ltd REG 316*4 1MRB520049-Uen / Rev. F
3-268
Fig. 3.5.26.2 Determining the settings for Z
A
, Z
B
, Z
C
, and Phi
according to X
d
', X
T
and Z
S
.
Setting: WarnAngle
The rotor angle is given by the triangle bounded by the instanta-
neous impedance and the impedances Z
A
and Z
B
. The protec-
tion, however, measures the angle between the instantaneous
voltage and the rotor voltages E
A
and E
B
,
which closely ap-
proximates the impedance triangle.
The setting for ‘WarnAngle’ can be set between 0° and 180° and
determines the rotor angle above which alarm of imminent slip-
ping is given.
With the ‘WarnAngle’ = 0°, alarm is given immediately the rotor
angle changes, providing it lies within the pick-up range.
'WarnAngle’ enables the operating status of the generator to be
corrected, because its rotor angle setting is reached before the
first slip. The machine can normally be stabilised for rotor angles
up to 135°, for example, by changing the excitation or switching
in compensators.
For a setting of ‘WarnAngle’ = 180°, alarm is not given until the
first slip takes place,
i.e. at the same time as the signal for zone 1
or zone 2.
Typical setting: WarnAngle = 110°.