Application Note

3 Fluke Corporation Saving energy through load balancing and load scheduling
The more data available to
analyze, the more likely you are
to come up with energy sav-
ing ideas. However, do not be
overwhelmed with data. In the
Power Log software, select only
the specific set of data you wish
to analyze at one time by check-
ing the appropriate checkboxes
on the top menu.
Once the data is downloaded
to the PC, select the “Frequency/
Unbalance Tab” in the Power
Log software. View data graphi-
cally by selecting the minimum,
maximum or average value of
each desired set of informa-
tion. (See Figure 3, Power Log
Frequency/Unbalance Tab). For
further analysis of the data,
export the data to a spread-
sheet by selecting “Export data”
under the File tab. You can then
compare the exact dates, times
and voltage unbalance values
to other plant data. Savvy engi-
neers and technicians, armed
with knowledge of what single-
phase equipment was operating
at what time and, with an up-
to-date one-line diagram of the
distribution system, can now
isolate loads and equalize them
across all three phases to correct
the unbalance problem.
Load scheduling
In addition to reducing energy
costs through load balancing,
technicians and engineers can
also create immediate energy
savings through load schedul-
ing. Load scheduling is the part
of energy load management that
minimizes demand.
Electric utilities charge large
commercial and industrial cus-
tomers a “peak demand penalty.”
This peak demand penalty is
in addition to the total usage
of electricity over the billing
period. “Maximum Demand” is
the maximum amount of elec-
tricity used by a customer at any
point in time. The utility must
be capable of supplying this
load, must size its distribution
equipment accordingly, and will
therefore charge the customer
to be able to meet this need.
This maximum electrical energy
usage, or demand, is averaged
over a 15 minute period, (typi-
cal), and determines the rate
schedule at which a customer
will be charged. Peak demand
is usually caused by a spike in
power consumption, most often
when multiple loads come on
simultaneously. These addi-
tional penalties can be high and
add significantly to the cost of
electrical energy. It only makes
sense to minimize the amount of
peak power being used, if at all
possible. Power logging provides
this opportunity.
If you are attempting to more
effectively schedule load opera-
tion, conduct power logging
recording sessions to measure
energy usage over time and
identify large loads that oper-
ate concurrently. Use one-line
diagrams to determine the
energy demand of various loads
and compare them to operating
needs. Do not look for just one
particular load to be causing the
problem. Quite often you must
work with operations personnel
and adjust a process by stagger-
ing cycling times, or complete
certain processes during off-
peak hours to reduce demand.
Engineers and operations man-
agement must work together
to review the electrical energy
bill and compare it to collected
power logging data to aid in
making the best plant opera-
tions and energy cost savings
decisions.
Figure 3. Power Log Frequency/Unbalance Tab. By selecting the various checkboxes at the
top of the Power Log software Frequency/Unbalance Tab the various sequence components
can be compared. In this comparison the negative sequence voltage component and its effect
upon amperage are plotted.
Unbalance
Aneg %
Unbalance
Vneg %
Date Time Unbalance An Avg Unbalance An Max Unbalance Vpos Min
10/9/2008 21:47:16 909ms 8.79 8.79 159.46
10/9/2008 21:47:26 909ms 8.79 8.8 159.46
10/9/2008 21:47:36 909ms 13.28 15.64 139.09
10/9/2008 21:47:46 909ms 15.63 15.64 139.09
10/9/2008 21:47:56 909ms 15.63 15.64 139.09
10/9/2008 21:48:06 909ms 15.63 15.64 139.09
10/9/2008 21:48:16 909ms 15.63 15.64 139.09
Data can be easily exported to a spreadsheet program for further analysis.