ABB Switzerland Ltd REG 316*4 1MRB520049-Uen / Rev. F
3-120
E. Setting instructions
Settings:
Voltage V-Setting
Delay Delay
Over or undervoltage MaxMin
Single or three-phase meas. NrOfPhases
By detecting excessively high voltages, the overvoltage function
prevents insulation breakdown of the windings of generator sta-
tors and power transformers and also excessive temperature
rise due to increased iron losses. Excessively high voltages of
longer duration are especially likely in the event of voltage
regulator failure. A time delay is set to prevent false tripping
during transients. Usually there are two voltage stages, both of
which are arranged to trip the protected unit.
Overvoltage setting (V-Setting)
The first stage is intended for moderate overvoltages of long du-
ration.
The second stage provides protection against high overvoltages
and is set to 70 % of the stator test voltage.
Where the rated voltages of the protected unit and the v.t’s differ,
the primary pick-up value in p.u. does not agree with the setting
of the protection and this has to be compensated using the
reference value of the A/D channel.
For example, for a generator rated voltage of U
GN
= 12 kV and a
primary v.t. rated voltage of U
1N
= 15 kV, the setting of the sec-
ond stage is
14 14
12
15
112
1
...
U
U
GN
N
==
Over/undervoltage setting (MaxMin)
This parameter enables the following operating modes to be
selected:
· MAX (1ph): Pick-up when the highest phase voltage ex-
ceeds the setting.
· MAX (3ph): Pick-up when the lowest phase voltage also
exceeds the setting. This setting is not permit-
ted, if the function is set to single-phase meas-
urement.
To Next Page
Loading...
