TM
5-811-1/AFJMAN
32-1080
a. Basis for design. The basis for design will
the installation including any pollution abatement
requirements, and annual costs for energy and
include a concise outline of functional features,
operating personnel wages.
including a description of existing systems and
b. Selection of electrical energy sources for exist-
other considerations affecting the design. In addi-
ing installations. Selection of an electrical energy
tion, a full description of any special requirements
source will be made when the existing source is
and justification for any proposed departure from
inadequate to supply the requirements for the
standard criteria are required.
(1) Exterior electrical distribution systems. The
facility being added. If the facility is incorporated
as a part of the overall installation master planning
description of exterior electrical distribution sys-
program, then the energy needs should have been
tems will include statements on all features rele-
forecast in the electrical systems master planning,
vant to the specific project as follows:
(2) Electrical power sources. Electrical charac-
and determination already made as to whether the
teristics of the electrical power supply to an entire
existing electrical energy source should be ex-
installation, or that portion of the installation
panded or whether some other alternative would be
involved, including circuit interrupting require-
more economical. When the master plan does not
ments and voltage regulation will be covered. A
provide the contemplated electrical requirements,
statement discussing the adequacy of the existing
an engineering study will be prepared.
electrical power supply (including primary feeders)
(1) Engineering studies. Outside energy sup-
at the point of take-off will be given. If the
plies will be evaluated based on the following:
electrical power source is inadequate, a statement
of the measures proposed to correct the deficiency
(b) Cost of energy to the installation, based
will be included. If a new electrical power source
on projected demand and usage requirements.
or local electrical generation is required, the vari-
(c) The suppliers ability to serve the present
ous possibilities will be covered, except where the
and the expected load for the next 5 years.
design directive has stipulated requirements. The
(d) System outages over the last five years,
advantages and disadvantages of various suitable
if available. Where outage information for at least
methods will be analyzed and cost comparisons
one year is not available, or where it is meaning-
submitted. Where a design directive permits a
less because it applies to a system since changed,
choice among alternatives, the merits of each
the system being considered will be evaluated on
alternative will be examined. If the use of a
the basis of the utilities reliability projections.
certain system or equipment has been directed and
(2) Electrical master planning. When an elec-
the designer recommends another approach, the
trical master plan is not available, existing facil-
designer will indicate any deviation from the
ities will be evaluated by making a physical
directed design and justify such deviations.
inspection of the existing facilities and accumulat-
(3) Loading. An estimate of total connected
ing the following data:
loads, power factors, demand factors, diversity
(a) Condition and characteristics of the ex-
factors, load profiles where required, resulting
isting off-site electrical energy sources including
demands, and sizes of proposed transformers to
data previously listed.
serve either the complete project or the various
(b) Number, condition, and characteristics of
portions involved will be provided. Transformer
prime and auxiliary generating plants.
peak loads and load cycling will be analyzed for
(c) Load information.
transformers when appropriate. Designer will coor-
dinate estimates with the using agency.
1-9. Design Analysis.
(4) Electrical distribution systems. The basis
for selection of primary and secondary distribution
The designer preparing plans and specifications for
work covered in this manual will also prepare an
voltages, and of overhead or underground construc-
accompanying design analysis. The design analysis
tion will be provided. The proposed type of conduc-
will completely cover the electrical design require-
tors such as copper or aluminum, bare or insu-
lated, where each type is used, and any special
ments for electrical systems necessary to the
basis for selection are required. Statements de-
project. The design analysis will also be used to
scribing pertinent standards of design such as
justify decisions recommended in concept or feasi-
voltage drop, maximum primary circuit interrupt-
bility studies, although a separate section is not
ing requirements, physical characteristics of over-
required if necessary material and computations
head or underground circuits, switching, circuit
are contained in a study, either in the body or in
protection, lightning protection, type of lighting
an appendix. The analysis will be submitted in two
units, and lighting intensities are required. Elec-
parts, a basis for design and design computations.
1-4
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