12-pulse, kVA rating, and frequency. Provide a
linear load value (kVA @ PF) which represents the
maximum linear load demand when non-linear loads
will also be in use. The generator manufacturer
will be required to meet the total harmonic
distortion limits established in IEEE Std 519.
Delete the non-linear load paragraph when non-linear
loads are not served from the engine-generator set.
Maximum Step Load Increase. Maximum step load
increase is used to account for the addition of
block loads. This affects engine-generator set
frequency and voltage output and usually initiate
governor and regulator response. The change in
engine-generator set output and the response of the
governor and regulator defines the transient loading
response. In the size range covered by this
specification (and for standby applications)
acquisition of full load in one step is typical for
major genset manufacturers (voltage deviation of 30%
or less, frequency deviation of + 5%, recovery time
3 to 5 seconds, typical). If the application
requires a more stringent response, specify the
actual maximum step load and add the allowable
deviations and recovery times to the Engine
Generator Set Parameter Schedule. If it is critical
enough to add these requirements, also add the
Transient Response Test from UFGS-16263A
DIESEL-GENERATOR SET STATIONARY 100-2500 KW, WITH
AUXILIARIES, to verify the results in the field. It
should be noted that this adds significant cost to
the cost of a genset.
Transient Recovery Criteria (short time duration).
Genset response and recovery times vary according to
the size of the set, the block load, and the
controls specified. Normal response to addition of
a block load will include dips in either output
voltage or frequency or both and possible
"overshoot" as the governor and voltage regulator
respond to bring the voltage and frequency back
within bandwidth. Normal response to lose of a
block load will include an upward spike in output
voltage or frequency back within bandwidth. The
Maximum Voltage and Frequency deviation apply to
undervoltage/underfrequency ("dips") from the
addition of block loads and any undershoot resulting
from the recovery of an upward spike, as well as
overvoltage/overfrequecy (upward spikes) from the
loss of block loads and any overshoot resulting from
the recovery of a dip.
Cost Impact. If stringent transient-response
requirements are specified the manufacturer may
select engine and generator models which have
nominal rating much larger than the service load;
may use an unnecessarily expensive governor; and may
use a higher inertia flywheel. The designer should
investigate what may actually be provided so that
SECTION 16264A
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