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 ELECTRICAL ENERGY SURVEYS
Section 5.
1. DATA FROM DEMAND SURVEYS. Electric bills may provide only the peak demand
for a month or the average of three or four highest peaks for a month,
depending on how the particular utility company computes maximum billing
demand. No indication is given of how this peak compares to the balance of
the demand profile for the interval, nor what combinations of loads caused the
peak. This information can only be acquired by monitoring key points in the
internal electrical system.
1.1 System Information. Each electrical system is different, but system
information for each follows a similar pyramid pattern, with overall system
information available at the peak and an increase in detailed information
available as the base is approached. Figures 9-15, 9-16, and 9-17 illustrate
the process of demand surveying in three phases.
1.2 Survey Starting Point. The survey should begin at the utility service
entrance. If a pulse initiator is in place, a demand analyzer can be
connected without need for voltage or current connections. If a pulse
initiator is not installed, additional connections will be required. Consult
the user manual for the demand analyzer before making any connections.
1.2.1 Utility Service Entrance. A utility service entrance demand profile
gives considerable information about the overall system. Comparing profiles
obtained from system monitoring will provide answers to the following
questions and will prove valuable in analyzing an electrical system.
(a) What is the peak facility load in kilowatts?
(b) What day of the week did it occur?
(c) Was the peak the same each day? If not, why?
(d) What is the after-hours load? Was it the same each day/night?
(e) Is there evidence of power wasted by starting equipment before hours
or letting it run unnecessarily during lunch or after hours?
(f) HOW does the peak compare with the utility company's demand charge
for the previous month?
(g) Could a slight change in startup time save money?
(h) HOW long did it take the facility to reach full power load after
starting time?
(i) Is there a tendency to anticipate quitting time?
(j) What is the maximum power factor of the load? What is the minimum?
9-37
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