TM
5-811-1
AFJMAN
32-1080
Distribution voltage
be divided into short sections by collector roadway
System voltage in the range of 5 kV to 34.5 kV.
systems.
Distribution voltage (sometimes referred to as
Low-voltage
primary voltage) is normally transformed down to
A class of nominal system voltage 1 kV or less.
utilization voltage with distribution transformers.
Major
Diversity factor
That part of the roadway system which serves as
The radio of the sum of the individual maximum
the principal network for through-traffic flow. The
demands of various subdivisions of the system to
routes connect areas of principal traffic generation
the maximum demand of the complete system.
Diversity Factor-(Sum of Ind. Max. Demands)/(Max
and important rural highways entering the city.
System Demand)
Maximum demand
Equipment pole
The greatest of all demands that have occurred
A pole used to support equipment, such as trans-
during a specified period of time.
formers, in addition to supporting conductors.
Maximum system voltage
Follow (power) current
The highest root-mean-square phase-to-phase volt-
The current from the connected power source that
age that occurs on the system under normal
flows through an arrester during and following the
operating conditions, and the highest root-mean-
passage of discharge current.
square phase-to-phase voltage for which equipment
and other system components are designed for
Guyed pole
satisfactory continuous operation without derating
Any pole strengthened with a guy wire.
of any kind. (When defining maximum system
voltage, voltage transients and temporary over-
High-fire-point liquid-insulated transformers
voltages cause by abnormal system conditions,
Same as less-flammable liquid-insulated trans-
such as faults, load rejection, etc., are excluded.
formers.
However, voltage transients and temporary over-
High-voltage
voltages may affect equipment life and operating
A class of nominal system voltages equal to or
performance as well as conductor insulation and
greater that 100,000 V.
are considered in equipment application.)
Intermediate
Medium-voltage
Those areas of a municipality often characterized
A class of nominal system voltage above 1 kV to
by moderately heavy nighttime pedestrian activity
99.9 kV.
such as in blocks having libraries, community
Multi-grounded
recreation centers, large apartment buildings, in-
A system grounding method where the neutral
dustrial buildings, or neighborhood retail stores.
conductor is carried along with the phase conduc-
Less-flammable liquid-insulated transformers
tors and grounded with at least four ground
Fire point not less that 300 degrees C. Fire point
connections per mile. See the MESC.
is the lowest temperature at which a liquid will
NADIR
give off vapors sufficient for continuous combus-
Lowest point.
tion.
Nominal system voltage
load factor
The root-mean-square phase-to-phase voltage by
The radio of the average load over a designated
which the system is designated and to which
period of time to the peak load occurring in that
certain operating characteristics of the system are
period. Load factor is used by utilities to deter-
related. (The nominal system voltage is near the
mine the excess capacity required to serve peak
voltage level at which the system normally oper-
loads.
ates. To allow for operating contingencies, systems
Loads factor-(Avg. Load)/(Peak Load)
generally operate at voltage levels about 5-10
percent below the maximum system voltage for
Local
which system components are designed.)
Roadways used primarily for direct access to resi-
dential, commercial, industrial, or other abutting
Nonflammable fluid-insulated transformers
property. They do not include roadways carrying
No flash or fire point and not flammable in air.
through traffic. Long local roadways will generally
Flash point is the temperature at which a liquid
GLOSSARY 2
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