DSEGenset DSEA108, Руководство оператора

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Operation
057-281 ISSUE: 1 Page 38 of 58
5.1.1.3 UNDER FREQUENCY ROLL OFF (UFRO)
NOTE: For further details of module configuration, refer to DSE Publication: 057-271
DSEA108 Configuration Suite PC Software Manual.
To help protect the alternator, output excitation is limited when generator output frequency is low, this
is known as Under Frequency Roll Off. This reduces the alternator output voltage which in turn,
reduces the
load on the generator. This can help to improve the generator’s reaction to step load
changes.
Turning the potentiometer clockwise increases the
Knee Point frequency. Below this frequency, the
generator output voltage is reduced. An Instantaneous Step can be enabled to reduce the voltage to a
percentage of the nominal frequency as soon as the frequency falls below the Knee Point setting.
After which the rate of reduction is configurable using DSE Configuration Suite PC Software between
0 % / Hz and 10% / Hz.
A typical setting to start the
Under Frequency Roll Off function is 3 Hz below nominal frequency.
As the frequency falls, the lower level is protected by the
Under Frequency trip. Should the frequency
fall below the trip level, the AVR excitation is disabled.
Example.
The following chart demonstrates Under Frequency Roll Off on a 50 Hz nominal system. The
Knee
Point is set to 47 Hz, Instantaneous Drop is set to 90% and Ramp Rate is set to 10% / Hz.
0
50
100
150
200
250
40 41 42 43 44 45 46 47 48 49 50
O
u
tp
u
t
V
o
lt
age
(V
A
C)
Nominal Frequency (Hz)
Under Frequency Roll Off With Instantaneous Step
Knee Point
(3 Hz below nominal)
Ramp Rate
(10% of nominal / Hz)
Example of Under Frequency Trip. Below this
frequency, the AVR disables excitation.
Instantaneous Step
(Drop to 90% of nominal)