TM
58111/AFJMAN
321080
SINLE LINE DIAGRAM
VECTOR DIAGRAMS
ASSUMED UTILITY RATES
CALCULATIONS
Losses  I2R
Energy charge
2
= [(2042  186 ) amperes] x 5 miles x 3 conductors x 0.278 ohms per mile

content
.035 per kWh
= 29.27 kw
Power factor
Line loss savings = 29.27 kW x 0.6 load factor x 4,000 hours x
content
.035
clause credit
= 59 a year
= 0.001 times value
in percent that
Power factor savings (increase 82 percent to 90 percent)
power factor (pf)
= 4,000 kW x 0.6 load factor x 4,000 hours x
content
.035 x [0.001 x 8]
is raised above a
= .690 a year
stipulated amount.
Total Savings = 59 + ,690 = 49 a Year
us Army Corps of Engineers
Figure 53. Average Energy Savings Example.
(3) Existing feeders. Circuit capability will be
miles will provide a sufficiently accurate determi
nation. For instance, taking the value for aerial
determined by measuring loads over a suitable
No. 4/0 AWG copper at 25 kV or 29.2 megavolt
period of time. Where such information is unavail
amperemiles and multiplying by (35/25)2 gives a
able, knowledge of the station maximum demand
value of 57.2 megavoltamperemiles which is al
most the value given in table 51. For under
mining an installation's demand factor on the
ground circuits, where proximity effects apply, a
basis of overall connected transformer capacity.
greater variation will be encountered, but esti
Circuit capability can be roughly evaluated by
mated demand loads are probably within the same
accuracy range.
and applying this factor; however, this method is
(2) New feeders. For new installations, with
too inaccurate as a basis for justifying new feeders
estimated demands based on requirements covered
or adding large loads.
b. Automatic circuit reclosers. Chapter 4 covers
in chapter 2 and estimated feeder lengths based on
the site plan, a determination of circuit require
provision of reclosing relays on outgoing feeder
ments can be made. Feeders will be large enough
circuit breakers at a main electric supply station.
Where a reclosing relay on a station circuit
to allow a growth factor of 25 percent of the design
maximum demand.
breaker does not provide a protective zone which
55