Recovery Time Back to Bandwidth. The designer
should determine the required recovery time for the
loads served. The recovery time to bandwidth is not
critical to operation of most equipment if the
voltage and frequency do not deviate from the
critical limits, or if momentary interruption is
acceptable to the loads being served. The primary
importance of this requirement is to ensure that the
engine generator set recovers and stabilizes after
load changes. Most engine generator sets can
respond to 100% block loads ;and return to voltage
and frequency bandwidths within 15 - 20 seconds,
depending on the size of the machine (RPM, relative
mass of the rotating elements, and ambient
conditions).
Transient Recover Time
[_____] seconds
with Step Load Increase
(Voltage).
Transient Recovery Time
[_____] seconds
with Step Load Increase
(Frequency).
Maximum Step Load Decrease (without shutdown). An
engine generator set should be capable of being
unloaded in a single step without tripping offline.
In these situations the voltage and frequency
transients are of no concern because there is no
load being served.
Nominal Step Load Decrease. Step load decrease is
used to account for dropping of block loads. This
affects engine-generator set frequency and voltage
output and usually initiates governor and regulator
response. The change in engine-generator set output
and the response of the governor and regulator
defines the transient loading response. Where the
load served may be sensitive to voltage and
frequency variation due to significant load
decrease, included the items below in the Parameter
Schedule. The Nominal Step Load Decrease provided
the genset manufacturer with the information
necessary to set the governor response for load
decreases such that an overspeed (over-frequency)
condition does not occur. The cost of
engine-generator sets increase by large percentages
for smaller frequency and voltage deviations from
bandwidth and improved recovery times. Carefully
analyze the user's need for restrictions on
If required add the following to the Engine
Generator Set Parameter Schedule and 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.
Nominal Step Load
[25] [50] [75]
Decrease at [_____] PF
percent of Service
SECTION 16264A
Page 20
Previous Page
