Multi-line 2 General Guidelines for Commissioning
DEIF A/S Page 14 of 19
Voltage droop
The AVR controls the generator voltage in a way which is comparable to the speed governor
controlling the prime mover speed.
This means that the generator AVR must have a voltage droop of 3-4% (voltage dropping 3-4%
from no load to full reactive load when the multi-line 2 has no control). In order to ensure equal
var sharing on parallel running generators, all generators must have the same voltage droop
setting.
Voltage range
When using the analogue interfacing, the resistor installed across the output terminals is
selected to obtain the necessary speed range. The voltage range must be defined similar to the
speed range for the governor.
The voltage range must be wide enough for the voltage droop and for the full loading of the gen-
set. A typical value is +/- 10% * U
NOM
. The necessary control signal level is often specified
depending on the AVR type.
Terminals
The AVR can either be prepared for analogue interfacing or digital interfacing. When analogue
interfacing is used, a +/- 20mA signal from the multi-line 2 is applied. This signal can be
converted to the necessary voltage level. When the digital interfacing is used, two relays are
used as increase/decrease outputs.
The terminals must be identified depending on the necessary interfacing. Some general
examples are shown in the illustrations in the chapter about ‘governor check’.
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