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4.2.2 Under Frequency Shed
Loads are shed on a time scale which is based on the
generator frequency droop. The loads will shed quickly
when the frequency droop is high (output frequency is
lower), and more slowly when the generator is running
close to rated frequency. The timing variation allows
large overloads to be shed very quickly, while allowing
the generator to ride through normal transients (such as
starting an AC compressor).
Figure 23 shows the under frequency shed timing for a
60 Hz generator set. If the underfrequency condition
persists, the load shed timing can be affected by load
shed acceleration. See Section 4.2.3.
Frequency (Hz)
Frequency
Droop (Hz)
Time (seconds)
>59 Hz
<1 Hz
Never Shed
58.5
1.5
5.4
57
3
4.3
56
4
3.4
54
6
1.8
<52.5 Hz
>7.5 Hz
0.3
Figure 23
Under Frequency Shed Timing for a 60Hz
Generator
4.2.3 Load Shed Acceleration
The load control module uses load shed acceleration to
shed
loads
more
quickly
if
an
overload
or
underfrequency condition persists.
If an overload
condition is not cleared by shedding a load, each
subsequent
load
will
shed
more
quickly.
The
acceleration is more pronounced for an underfrequency
shed.
4.2.4 Changing Settings
The Generator Maximum Percent Capacity and
Generator
Overloaded
Percent
settings
can
be
changed using a laptop computer connected to the
RDC2 or DC2 controller and Kohler
r
SiteTech
t
software. The load control settings are found in the
Genset System Configuration group. See Figure 24
and TP-6701, SiteTech Software Operation Manual.
Set the Generator Overload Percent at least 10% higher
than the Generator Maximum Percent Capacity.
1
tt1574
1. LCM settings
Figure 24
SiteTech Screen
