ABB REG316 4 Series Operating Instructions Manual page 232

ABB Switzerland Ltd
E. Setting instructions
There are often several stages of frequency protection using
several single-stage relays.
Settings:
Frequency
Delay
Undervoltage blocking
Under or over frequency
Frequency protection is used either to protect synchronous
machines and prime-movers against the effects of operating at
under or overfrequency or for load-shedding in the event of an
overload.
The adverse effects in the former case prevented by the fre-
quency protection are:
excessive temperature rise and additional iron losses in the
·
generator
damage to the generator and the prime-mover by vibration.
·
Some synchronous machines are subject to severe vibration if
they are operated at speeds other than their rated speed.
Vibration occurs more usual at speeds below rated frequency,
but can occur both above and below. A complete scheme often
comprises therefore 4 stages, two for alarm and tripping for
overfrequency and two for alarm and tripping for underfre-
quency. Tripping is delayed to avoid the risk of maloperation
during transients.
Typical settings:
1. Protection of machines
1st. stage
Alarm
Frequency (Hz) 51.0
Delay (s) 1.5
BlockVoltage 0.6
MaxMin
MAX
Table 3.5.18.1 Typical settings for alarm and tripping stages
3-194
REG 316*4 1MRB520049-Uen / Rev. F
Frequency
Delay
BlockVoltage
MaxMin
2nd. stage 3rd. stage
Tripping Alarm
52.0 49.0
3 1.5
0.6 0.6
MAX MIN
4th. stage
Tripping
48.0
3
0.6
MIN