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Title[ANSI C84.1-2006] Electric Power Systems and Equipment - Voltage Ratings (60 Hertz)
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Page 1

ANSI C84.1-2006

American National Standard

for Electric Power Systems
and Equipment—

Voltage Ratings (60 Hertz)

Page 11

ANSI C84.1-2006



For Electric Power Systems and Equipment—
Voltage Ratings (60 Hertz)

1 Scope and purpose

1.1 Scope

This standard establishes nominal voltage ratings and operating tolerances for 60-hertz electric power
systems above 100 volts. It also makes recommendations to other standardizing groups with respect to
voltage ratings for equipment used on power systems and for utilization devices connected to such

This standard includes preferred voltage ratings up to and including 1200 kV maximum system voltage,
as defined in the standard.

In defining maximum system voltage, voltage transients and temporary overvoltages caused by abnormal
system conditions such as faults, load rejection, and the like are excluded. However, voltage transients
and temporary overvoltages may affect equipment operating performance and are considered in
equipment application.

1.2 Purpose

The purposes of this standard are to:

(1) Promote a better understanding of the voltages associated with power systems and utilization
equipment to achieve overall practical and economical design and operation

(2) Establish uniform nomenclature in the field of voltages
(3) Promote standardization of nominal system voltages and ranges of voltage variations for

operating systems
(4) Promote standardization of equipment voltage ratings and tolerances
(5) Promote coordination of relationships between system and equipment voltage ratings and

(6) Provide a guide for future development and design of equipment to achieve the best possible

conformance with the needs of the users
(7) Provide a guide, with respect to choice of voltages, for new power system undertakings and

for changes in older ones

2 Definitions

2.1 system or power system: The connected system of power apparatus used to deliver electric
power from the source to the utilization device. Portions of the system may be under different ownership,
such as that of a supplier or a user.

2.2 system voltage terms. As used in this document, all voltages are rms phase-to-phase, except
that the voltage following a slant-line is an rms phase-to-neutral voltage.

2.2.1 system voltage: The root-mean-square (rms) phase-to-phase voltage of a portion of an
alternating-current electric system. Each system voltage pertains to a portion of the system that is
bounded by transformers or utilization equipment.

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ANSI C84.1-2006


2.2.2 nominal system voltage: The voltage by which a portion of the system is designated, and to
which certain operating characteristics of the system are related. Each nominal system voltage pertains
to a portion of the system bounded by transformers or utilization equipment.

The nominal voltage of a system is near the voltage level at which the system normally operates. To
allow for operating contingencies, systems generally operate at voltage levels about 5–10% below the
maximum system voltage for which system components are designed.

2.2.3 maximum system voltage: The highest system voltage that occurs under normal operating
conditions, and the highest system voltage for which equipment and other components are designed for
satisfactory continuous operation without derating of any kind.

2.3 service voltage: The voltage at the point where the electrical system of the supplier and the
electrical system of the user are connected.

2.4 utilization voltage: The voltage at the line terminals of utilization equipment.

2.4.1 nominal utilization voltage: The voltage rating of certain utilization equipment used on the

The nominal system voltages contained in table 1 apply to all parts of the system, both of the supplier and
of the user. The ranges are given separately for service voltage and for utilization voltage, these normally
being at different locations. It is recognized that the voltage at utilization points is normally somewhat
lower than at the service point. In deference to this fact, and the fact that integral horsepower motors, or
air conditioning and refrigeration equipment, or both, may constitute a heavy concentrated load on some
circuits, the rated voltages of such equipment and of motors and motor-control equipment are usually
lower than nominal system voltage. This corresponds to the range of utilization voltages in
table 1. Other utilization equipment is generally rated at nominal system voltage.

3 System voltage classes

3.1 low voltage (LV): A class of nominal system voltages 1000 volts or less.

3.2 medium voltage (MV): A class of nominal system voltages greater than 1000 volts and less than
100 kV.

3.3 high voltage (HV): A class of nominal system voltages equal to or greater than 100 kV and equal
to or less than 230 kV.

3.4 extra-high voltage (EHV): A class of nominal system voltages greater than 230 kV but less than
1000 kV.

3.5 ultra-high voltage (UHV): A class of nominal system voltages equal to or greater than 1000 kV.

4 Selection of nominal system voltages

When a new system is to be built or a new voltage level introduced into an existing system, one (or more)
of the preferred nominal system voltages shown in boldface type in table 1 should be selected. The
logical and economical choice for a particular system among the voltages thus distinguished will depend
upon a number of factors, such as the character and size of the system.

Other system voltages that are in substantial use in existing systems are shown in lightface type.
Economic considerations will require that these voltages continue in use and in some cases may require
that their use be extended; however, these voltages generally should not be utilized in new systems or in
new voltage levels in existing systems.

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ANSI C84.1-2006



Standard *

Room fan-coil air conditioners
Rotating electrical machinery
AC induction motors
Cylindrical rotor synchronous generators
Salient pole synchronous generator and condensers
Synchronous motors
Universal motors
Self-contained humidifiers
Self-contained mechanically refrigerated drinking-water coolers
Shunt power capacitors
Solenoid valves for liquid and gaseous flow
Static power conversion equipment
Surge arresters
Transformers, regulators, and reactors
Arc furnace transformers
Constant-current transformers
Current-limiting reactors
Distribution transformers, conventional subway-type
Dry type
Instrument transformers
Power transformers
Rectifier transformers
Secondary network transformers
Step-voltage and induction-voltage regulators
Three-phase load-tap-changing transformers
Unit ventilators
Unitary air-conditioning equipment
Commercial and industrial unitary air-conditioning equipment
Unitary heat-pump equipment
Wiring devices

ARI 441

ANSI C50 Series and



ARI 760

ANSI C62.1, IEEE C62.11 & NEMA LA 1

ANSI C57 Series

ARI 330
ARI 210

ARI 240

ANSI C73 Series

*See list of organizations in Section D2.



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ANSI C84.1-2006


D.2 Organizations Referred to in Section D.1

AEIC Association of Edison Illuminating Companies
P.O. Box 2641
Birmingham, AL 35291-0992

AHAM Association of Home Appliance Manufacturers
1111 19th Street NW, Suite 402
Washington, DC 20036

AMCA Air Movement and Control Association
30 West University Drive
Arlington Heights, IL 60004

ANSI American National Standards Institute, Inc
11 West 42nd Street, 13th Floor
New York, NY 10036

ARI Air Conditioning and Refrigeration Institute
4301 N. Fairfax Drive; Suite 425
Arlington, VA 22203

CS Commercial Standards
Office of Commodity Standards
National Institute of Standards and Technology,
U.S. Department of Commerce
Gaithersburg, MD 20899-0001

IBR* Hydronics Institute
35 Russo Place,
P.O. Box 218
Berkeley Heights, NJ 07922

IEEE The Institute of Electrical and Electronics
Engineers, Inc.
445 Hoes Lane
Piscataway, NJ 08855

ICEA Insulated Cable Engineers Association
PO Box 1568
Carrollton, GA 30112

NEMA National Electrical Manufacturers Association
1300 North 17th Street; Suite 1847
Rosslyn, VA 22209

*Institute of Boiler and Radiator Manufacturers.


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