NEMA Standards Publication

ANSI C84.1-2016
Electric Power Systems
and Equipment —
Voltage Ratings
(60 Hertz)

National Electrical Manufacturers Association

 ANSI C84.1 -201 6
Page i

ANSI C84.1 -201 6

American National Standard for

Electric Power Systems and Equipment—
Voltage Ratings (60 Hertz)
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Secretariat:
National Electrical Manufacturers Association
Approved: June 9, 201 6
American National Standards Institute, Inc.

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ANSI C84.1 -201 6
Page ii
NOTICE AND DISCLAIMER
The information in this publication was considered technically sound by the consensus of persons
engaged in the development and approval of the document at the time it was developed. Consensus
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American National Standards Institute, Inc. (ANSI) standards and guideline publications, of which the
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AMERICAN Approval of an American National Standard requires verification by the

American National Standards Institute, Inc. (ANSI) that the requirements
NATIONAL for due process, consensus, and other criteria for approval have been met
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The existence of an American National Standard does not in any respect
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CAUTION NOTICE: This American National Standard may be revised or
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Published by

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1 300 North 1 7th Street, Suite 900, Rosslyn, Virginia 22209
© 201 6 National Electrical Manufacturers Association. All rights, including translation into other
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permission of the publisher.

Printed in the United States of America

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ANSI C84.1 -201 6
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CONTENTS

Foreword........................................... ................................................... .......................................... .... iv

1 Scope and Purpose ................................................... ................................................... ...................... 1

1 .1 Scope ................................................... ................................................... ................................. 1
1 .2 Purpose ........................................... ................................................... ...................................... 1

2 Definitions ....................................... ................................................... ................................................. 1

3 System Voltage Classes ........................................... ................................................... ....................... 2

4 Selection of Nominal System Voltages .......................................... ................................................... .. 2

5 Explanation of Voltage Ranges ................................................... ................................................... .... 3

5.1 Application of Voltage Ranges ............................................ ................................................... .. 3
5.1 .1 Range A—Service Voltage ................................................... ....................................... 3
5.1 .2 Range A—Utilization Voltage ........................................... ............................................ 3
5.1 .3 Range B—Service and Utilization Voltages .......................................... ....................... 3
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5.1 .4 Outside Range B—Service and Utilization Voltages ................................................... 3

6 Voltage Ratings for 60-Hz Electric Equipment ................................................... ................................ 4

6.1 General ........................................... ................................................... ....................................... 4
6.2 Recommendation ................................................... ................................................... ............... 4
Annex A Principal Transformer Connections to Supply the System Voltages of Table 1 ...................... 7
Annex B Illustration of Voltage Ranges of Table 1 ................................................... .............................. 8
Annex C Polyphase Voltage Unbalance ......................................... ................................................... ..... 9
Annex D Applicable Standards ................................................... ................................................... ....... 1 1

TABLES
Table 1 ................................................... ................................................... ................................................... . 5

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Foreword (This Foreword is not part of American National Standard C84.1 )

This standard supersedes ANSI C84.1 -201 1 American National Standard for Electric Power Systems and
Equipment—Voltage Ratings (60Hz).
With the 201 6 revision, a 690/400V category has been added to the Low Voltage Class in table 1 , and a
paragraph discussing Conservation Voltage Reduction (CVR) has been added to Annex B.
In 1 942, the Edison Electric Institute published the document Utilization Voltage Standardization
Recommendations , EEI Pub. No. J-8. Based on that early document, a joint report was issued in 1 949 by
the Edison Electric Institute (EEI Pub. No. R6) and the National Electrical Manufacturers Association
(NEMA Pub. No. 1 1 7). This 1 949 publication was subsequently approved as American National Standard
EEI-NEMA Preferred Voltage Ratings for AC Systems and Equipment, ANSI C84.1 -1 954.
American National Standard C84.1 -1 954 was a pioneering effort in its field. It not only made carefully
considered recommendations on voltage ratings for electric systems and equipment, but also contained a
considerable amount of much-needed educational material.
After ANSI C84.1 -1 954 was prepared, the capacities of power supply systems and customers' wiring
systems increased and their unit voltage drops decreased. New utilization equipment was introduced and
power requirements of individual equipment were increased. These developments exerted an important
influence both on power systems and equipment design and on operating characteristics.
In accordance with American National Standards Institute policy requiring periodic review of its standards,
American National Standards Committee C84 was activated in 1 962 to review and revise American
National Standard C84.1 -1 954, the Edison Electric Institute and National Electrical Manufacturers
Association (NEMA)being named cosponsors for the project. Membership on the C84 Committee
represented a wide diversity of experience in the electrical industry. To this invaluable pool of experience
were added the findings of the following surveys conducted by the committee:
a) A comprehensive questionnaire on power system design and operating practices, including
measurement of actual service voltages (approximately 65,000 readings were recorded, coming
from all parts of the United States and from systems of all sizes, whether measured by number of
customers or by extent of service areas)
b) A sampling of single-phase distribution transformer production by kilovolt-amperes and primary
voltage ratings to determine relative uses of medium voltages
c) A survey of utilization voltages at motor terminals at approximately 20 industrial locations
The worth of any standard is measured by the degree of its acceptance and use. After careful
consideration, and in view of the state of the art and the generally better understanding of the factors
involved, the C84 Committee concluded that a successor standard to ANSI C84.1 -1 954 should be
developed and published in a much simplified form, thereby promoting ease of understanding and hence
its acceptance and use. This resulted in the approval and publication of American National Standard
C84.1 -1 970, followed by its supplement, ANSI C84.1 a-1 973, which provided voltage limits established for
the 600V nominal system voltage.
The 1 977 revision of the standard incorporated an expanded Foreword that provided a more complete
history of this standard’s development. The 1 970 revision included a significantly more useful table 1 (by
designating “preferred” system voltages), the 1 977 revision provided further clarity, and the 1 982 revision
segmented the system voltages into the various voltage classes.
With the 2006 revision, the scope expanded to include voltages above 230 kV. This increased voltage
range was previously covered by IEEE Std 1 31 2-1 993 (R2004), IEEE Standard Preferred Voltage
Ratings for Alternating-Current Electrical Systems and Equipment Operating at Voltages Above 230 kV
Nominal and its predecessor, ANSI C92.2-1 987. In addition, standard nominal system voltages and
,

voltage ranges were extended to include maximum system voltages of up to and including 1 200 kV.

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With the 201 1 revision, table 1 was modified to reflect changes in lighting characteristics. Note 1 allowed
lower utilization voltages for non-lighting circuits. Modern lighting equipment does not need this special
treatment. Note 1 was dropped and the table was updated with the lower voltages. This treats lighting
equipment like all other utilization equipment.
Suggestions for improvement of the standard are welcome. They should be sent to NEMA, 1 300 North
1 7 th Street, Rosslyn, VA 22209.
This standard was processed and approved for submittal to ANSI by Accredited Standards Committee on
Preferred Voltage Ratings for AC Systems and Equipment, C84. Committee approval of the standard
does not necessarily imply that all committee members voted for its approval. At the time it approved this
standard, the C84 Committee had the following members:

Daniel Ward, Chairman

Khaled Masri (NEMA), Secretary

Organizations Represented Name of Representative

Eversource Energy Lauren Gaunt
Conrad Technical Services Larry Conrad
Dominion Power John Bruce
Dominion Power Daniel Ward
Enphase Energy John Berdner
NRECA Robert
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Standard
EPRI Tom Key
FirstEnergy Technologies Tim Croushore
GE Energy Management Lavelle Freeman
GW Technical Services Gary Weidner
NorthWestern Energy Jim Cole
NRECA Tony Thomas
Quanta Technology James Burke
Baldor Electric Roger Daugherty
Siemens Ted Olsen
Smullin Engineering, Inc. Gary Smullin
SolarCity Michael McCarty
T. David Mills Associates T. David Mills
Walling Energy Systems Consulting Reigh Walling

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1 Scope and Purpose

1 .1 Scope
This standard establishes nominal voltage ratings and operating tolerances for 60Hz electric power
systems above 1 00 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
systems.
This standard includes preferred voltage ratings up to and including 1 200 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:
a) Promote a better understanding of the voltages associated with power systems and utilization
equipment to achieve overall practical and economical design and operation
b) Establish uniform nomenclature in the field of voltages
c) Promote standardization of nominal system voltages and ranges of voltage variations for
operating systems
d) Promote standardization of equipment voltage ratings and tolerances
e) Promote coordination of relationships between system and equipment voltage ratings and
tolerances
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f) Provide a guide for future development and design of equipment to achieve the best possible
conformance with the needs of the users
g) 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.
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.
NOTE: 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 5–1 0% below the maximum system
voltage for which system components are designed.

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Page 2

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
continuous satisfactory 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
system.
NOTE: 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 utilization voltage is normally somewhat lower than the service voltage. 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.
2.5 voltage level: Voltage level is a generalized term that is synonymous with the rms voltage
averaged over 1 0 minutes.
3 System Voltage Classes
3.1 Low Voltage (LV): A class of nominal system voltages 1 000 volts or less.
3.2 Medium Voltage (MV): A class of nominal system voltages greater than 1 000 volts and less than
1 00 kV.
3.3 High Voltage (HV): A class of nominal system voltages equal to or greater than 1 00 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
1 000 kV.
3.5 Ultra-High Voltage (UHV): A class of nominal system voltages equal to or greater than 1 000 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 stay 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.
The 41 60V, 6900V, and 1 3,800V three-wire systems are particularly suited for industrial systems that
supply predominantly polyphase loads, including large motors, because these voltages correspond to the
standard motor ratings of 4000 volts, 6600 volts, and 1 3,200 volts, as is explained further in 2.4.1 . It is not
intended to recommend the use of these system voltages for utility primary distribution, for which four-wire
voltages of 1 2470Y/7200 volts or higher should be used.

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5 Explanation of Voltage Ranges

For any specific nominal system voltage, the voltages actually existing at various points at various times
on any power system, or on any group of systems, or in the industry as a whole, usually will be distributed
within the maximum and minimum voltages shown in table 1 . The design and operation of power systems
and the design of equipment to be supplied from such systems should be coordinated with respect to
these voltages so that the equipment will perform satisfactorily in conformance with product standards
throughout the range of actual utilization voltages that will be encountered on the system. To further this
objective, this standard establishes, for each nominal system voltage, two ranges for service voltage and
utilization voltage variations, designated as Range A and Range B, the limits of which are given in table 1 .
These limits shall apply to sustained voltage levels and not to momentary voltage excursions that may
result from such causes as switching operations, motor starting currents, and the like.
5.1 Application of Voltage Ranges
5.1 .1 Range A—Service Voltage
Electric supply systems shall be so designed and operated that most service voltages will be within the
limits specified for Range A. The occurrence of service voltages outside of these limits should be
infrequent.
5.1 .2 Range A—Utilization Voltage
User systems shall be so designed and operated that with service voltages within Range A limits, most
utilization voltages will be within the limits specified for this range.
Utilization equipment shall be designed and rated to give fully satisfactory performance throughout this
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5.1 .3 Range B—Service and Utilization Voltages

Range B includes voltages above and below Range A limits that necessarily result from practical design
and operating conditions on supply or user systems, or both. Although such conditions are a part of
practical operations, they shall be limited in extent, frequency, and duration. When they occur, corrective
measures shall be undertaken within a reasonable time to improve voltages to meet Range A
requirements.
Insofar as practicable, utilization equipment shall be designed to give acceptable performance in the
extremes of the range of utilization voltages, although not necessarily as good performance as in Range A.
5.1 .4 Outside Range B—Service and Utilization Voltages
It should be recognized that because of conditions beyond the control of the supplier or user, or both,
there will be infrequent and limited periods when sustained voltages outside Range B limits will occur.
Utilization equipment may not operate satisfactorily under these conditions, and protective devices may
operate to protect the equipment.
When voltages occur outside the limits of Range B, prompt, corrective action shall be taken. The urgency
for such action will depend upon many factors, such as the location and nature of the load or circuits
involved, and the magnitude and duration of the deviation beyond Range B limits.

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6 Vo l tag e R ati n g s fo r 60H z El ectri c E q u i pm en t

6. 1 G en eral

This standard includes information, as given in Annex C, to assist in the understanding about the effects
of unbalanced voltages on utilization equipment applied in polyphase systems.
6. 2 R ecom m en d ati o n

Insofar as practicable, whenever electric equipment standards are revised:

a) Nameplate voltage ratings should be changed as needed in order to provide a consistent
relationship between the ratings for all equipment of the same general class and the nominal
system voltage on the portion of the system on which they are designed to operate.
b) The voltage ranges for which equipment is designed should be changed as needed in order to be
in accordance with the ranges shown in table 1 .
The voltage ratings in each class of utilization equipment should be either the same as the nominal
system voltages or less than the nominal system voltages by the approximate ratio of 1 1 5 to 1 20.

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Table 1
Standard Nominal System Voltages and Voltage Ranges (Preferred system voltages in bold-face type)
Nominal System Voltage Nominal Voltage Range A Voltage Range B
Utilization (Note b) (Note b)
VOLTAGE

Voltage Maximum Minimum Maximum Minimum

CLASS

(Note a) (Note h)
2-wire 3-wire 4-wire 2-wire Utilization and Service Utilization Utilization and Service Utilization
3-wire Service Voltage Voltage Voltage Service Voltage Voltage Voltage
4-wire (Note c)
Single-Phase Systems
1 20 115 1 26 114 1 08 1 27 110 1 04
1 20/240 1 1 5/230 1 26/252 1 1 4/228 1 08/21 6 1 27/254 1 1 0/220 1 04/208
Three-Phase Systems
208Y/1 20 200 21 8Y/1 26 1 97Y/1 1 4 1 87Y/1 08 220Y/1 27 1 91 Y/1 1 0 1 80Y/1 04
Low Voltage

(Note d) (Note i) (Note i)

240/1 20 230/1 1 5 252/1 26 228/1 1 4 21 6/1 08 254/1 27 220/1 1 0 208/1 04
240 230 252 228 21 6 254 220 208
480Y/277 460Y/266 504Y/291 456Y/263 432Y/249 508Y/293 440Y/254 41 6Y/240
480 460 504 456 432 508 440 41 6
600 575 630 570 540 635 550 520
(Note e) (Note e) (Note e)
690Y/400 660 720 655 630 725 635 61 0
2400 2520 from Standard
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2540 2280 2080
41 60Y/2400 4370/2520 4050Y/2340 3740Y/21 60 4400Y/2540 3950Y/2280 3600Y/2080
41 60 4370 4050 3740 4400 3950 3600
4800 5040 4680 4320 5080 4560 41 60
6900 7240 6730 621 0 7260 6560 5940
8320Y/4800 8730Y/5040 81 1 0Y/4680 8800Y/5080 7900Y/4560
1 2000Y/6930 1 2600Y/7270 1 1 700Y/6760 1 2700Y/7330 1 1 400Y/6580 (Note f)
1 2470Y/7200 1 3090Y/7560 1 21 60Y/7020 (Note f) 1 3200Y/7620 1 1 850Y/6840
1 3200Y/7620 1 3860Y/8000 1 2870Y/7430 1 3970Y/8070 1 2504Y/7240
Medium Voltage

1 3800Y/7970 1 4490Y/8370 1 3460Y/7770 1 4520Y/8380 1 31 1 0Y/7570

1 3800 1 4490 1 3460 1 2420 1 4520 1 31 1 0 1 1 880
20780Y/1 2000 21 820Y/1 2600 20260Y/1 1 700 22000Y/1 2700 1 9740Y/1 1 400
22860Y/1 3200 24000Y/1 3860 22290Y/1 2870 24200Y/1 3970 21 720Y/1 2540 (Note f)
23000 241 50 22430 (Note f) 24340 21 850
24940Y/1 4400 261 90Y/1 51 20 24320Y/1 4040 26400Y/1 5240 23690Y/1 3680
34500Y/1 9920 36230Y/20920 33640Y/1 9420 3651 0Y/21 080 32780Y/1 8930
34500 36230 33640 3651 0 32780
Maximum
Voltage (Note g)
46000 48300
69000 72500
Continued on next page

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Table 1
Standard Nominal System Voltages and Voltage Ranges (continued)
(Preferred system voltages in bold-face type)

Nominal System Voltage Nominal Maximum

Utilization Voltage
VOLTAGE Voltage (note g)
CLASS (Note a) (Note h)
2-wire 3-wire 4-wire
1 1 5000 1 21 000
1 38000 1 45000
High Voltage 1 61 000 1 69000
230000 242000
345000 362000
400000 420000
Extra-High Voltage 500000 550000
765000 800000
1 1 00000 1 200000
Ultra-High
Voltage

NOTES:
a) Three-phase three-wire systems are systems in which only the three-phase conductors are carried out from
the source for connection of loads. The source may be derived from any type of three-phase transformer
connection, grounded or ungrounded. Three-phase four-wire systems are systems in which a grounded
neutral conductor is also carried out from the source for connection of loads. Four-wire systems in table 1 are
designated by the phase-to-phase voltage, followed by the letter Y (except for the 240/1 20V delta system), a
slant line, and the phase-to-neutral voltage. Single-phase services and loads may be supplied from either
single-phase or three-phase systems. The principal transformer connections that are used to supply single-
phase and three-phase systems are illustrated in Annex A.
b) The voltage ranges in this table are illustrated in Annex B.
c) For 1 20-600V nominal systems, voltages in this column are maximum service voltages. Maximum utilization
voltages would not be expected to exceed 1 25 volts for the nominal system voltage of 1 20, nor appropriate
multiples thereof for other nominal system voltages through 600 volts.
d) A modification of this three-phase, four-wire system is available as a 1 20/208YV service for single-phase,
three-wire, open-wye applications.
e) Certain kinds of control and protective equipment presently available have a maximum voltage limit of 600
volts; the manufacturer or power supplier or both should be consulted to assure proper application.
f) Utilization equipment does not generally operate directly at these voltages. For equipment supplied through
transformers, refer to limits for nominal system voltage of transformer output.
g) For these systems, Range A and Range B limits are not shown because, where they are used as service
voltages, the operating voltage level on the user’s system is normally adjusted by means of voltage
regulators or load tap-changers to suit their requirements.
h) Nominal utilization voltages are for low-voltage motors and control.
i) Many 220V motors were applied on existing 208V systems on the assumption that the utilization voltage
would not be less than 1 87V. Caution should be exercised in applying the Range B minimum voltages of
table 1 to existing 208V systems supplying such motors.

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Annex A
(informative)
Principal Transformer Connections to Supply the System Voltages of Table 1
(See Figure A1 )

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Figure A1
NOTES:
a) The above diagrams show connections of transformer secondary windings to supply the nominal system
voltages of table 1 . Systems of more than 600 volts are normally three-phase and supplied by connections
(3), (5) ungrounded, or (7). Systems of 1 20-600 volts may be either single-phase or three phase, and all of
the connections shown are used to some extent for some systems in this voltage range.
b) Three-phase, three-wire systems may be solidly grounded, impedance grounded, or ungrounded but are not
intended to supply loads connected phase to-neutral (as the four-wire systems are).
c) In connections (5) and (6) the ground may be connected to the midpoint of one winding as shown (if
available), to one phase conductor ("corner" grounded), or omitted entirely (ungrounded).
d) Single-phase services and single-phase loads may be supplied from single-phase systems or from three-
phase systems. They are connected phase-to-phase when supplied from three-phase, three-wire systems
and either phase-to-phase or phase-to-neutral from three-phase, four-wire systems.

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Annex B
Illustration of Voltage Ranges of Table 1
Figure B1 shows the basis of the Range A and Range B limits of table 1 . The limits in table 1 were
determined by multiplying the limits shown in this chart by the ratio of each nominal system voltage to the
1 20V base. [For exceptions, see note (c) to Figure B1 .]
A technique commonly called Conservation Voltage Reduction (CVR) is sometimes used for energy and
or demand reduction. Determination of the value of CVR is beyond the scope of this standard. However, it
is recommended that the application of CVR should be limited to voltages in Range A for normal
operation. Range B should be reserved for emergency, infrequent operation. CVR systems should not be
designed to operate below Range B for any condition.

(informative)
Figure B1
NOTES:
a) The shaded portion of Range A does not apply to 1 20-600-volt systems. See note (c) to table 1 .
b) The difference between minimum service and minimum utilization voltages is intended to allow for voltage
drop in the customer's wiring system. This difference is greater for service at more than 600 volts to allow
for additional voltage drop in transformations between service voltage and utilization equipment.
c) The Range B utilization voltage limits in table 1 for 2400V through 1 3,800V systems are based on 90% and
1 1 0% of the voltage ratings of the standard motors used in these systems with some having a slight
deviation from this figure.

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Annex C
(Informative)
Polyphase Voltage Unbalance
C.1 Introduction
Studies on the subject of three-phase voltage unbalance indicate that: (1 ) all utility-related costs required
to reduce voltage unbalance and all manufacturing-related costs required to expand a motor's
unbalanced voltage operating range are ultimately borne directly by the customer, (2) utilities' incremental
improvement costs are maximum as the voltage unbalance approaches zero and decline as the range
increases, and (3) manufacturers' incremental motor-related costs are minimum at zero voltage
unbalance and increase rapidly as the range increases.
When these costs, which exclude motor-related energy losses, are combined, curves can be developed
that indicate the annual incremental cost to the customer for various selected percent voltage unbalance
limits.
The optimal range of voltage unbalance occurs when the costs are minimum.
a) Field surveys tend to indicate that the voltage unbalances range from 0–2.5 percent to 0–4.0
percent with the average at approximately 0–3.0 percent
b) Approximately 98 percent of the electric supply systems surveyed are within the 0–3.0 percent
voltage-unbalance range, with 66 percent at 0–1 .0 percent or less

C.2 Recommendation
Electric supplyGet
systems should be designed and operated to limit the maximum voltage unbalance to 3
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percent when measured at the electric-utility revenue meter under no-load conditions.
This recommendation should not be construed as expanding the voltage ranges prescribed in 5. If the
unbalanced voltages of a polyphase system are near the upper or lower limits specified in table 1 , Range
A or Range B, each individual phase voltage should be within the limits in table 1 .

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ANSI C84.1 -201 6
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C.3 Calculation for Voltage Unbalance
Voltage unbalance of a polyphase system is expressed as a percentage value and calculated as follows:

Percent voltage unbalance =1 00 ×( maximum deviation from average V)

( Average Voltage)
Example: with phase-to-phase voltages of 230, 232, and 225, the average is 229; the maximum deviation
from average is 4; and the percent unbalance is (1 00 × 4)/229 = 1 .75 percent.
C.4 Derating for Unbalance
The rated load capability of polyphase equipment is normally reduced by voltage unbalance. A common
example is the derating factor, from figure C1 , used in the application of polyphase induction motors.

Figure C1
Derating factor
NOTE: See 1 4.36 of NEMA MG 1 -2009 for more complete information about the derating factor.

C.5 Protection from Severe Voltage Unbalance

User systems should be designed and operated to maintain a reasonably balanced load.
In severe cases of voltage unbalance, consideration should be given to equipment protection by applying
unbalance limit controls.

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 ANSI C84.1 -201 6
Page 1 1

Annex D
(Informative)
Applicable Standards
D.1 List of Standards
The following is a partial list of standards (by general number) for equipment from which voltage ratings
and other characteristics can be obtained.

Equipment Standard
Air-conditioning and refrigerating equipment nameplate ARI 1 1 0
voltages
Air filter equipment ARI 680
Ammonia compressors and compressor units ARI 51 0
Application, installation, and servicing of unitary systems ARI Series
Automatic commercial ice makers ARI 81 0
Cable terminating devices (power) IEEE 48
Central forced-air electric heating equipment ARI Series
Central-station air-handling units ARI 430
Connectors for electric utility applications ANSI C1 1 9.1
Definite purpose magnetic contactors ARI 780
Dehumidifiers ANSI/AHAM DH-1
Electrical measuring instruments ANSI C39 Series
Electrical power insulators ANSI C29 Series
Electricity metering ANSI C1 2 Series
Forced circulation, free-delivery air coolers for refrigeration ARI 420
Gas-firedGet furnaces
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Series
Industrial control apparatus ANSI/NEMA ICS Series
Insulated conductors ANSI/NFPA 70
AEIC Series
ICEA Series
Lamps
Bactericidal lamps ANSI C78 Series
Electrical discharge lamp
Incandescent lamps
Lamp ballasts ANSI C82 Series
Low-voltage fuses ANSI/NEMA FU 1
Low-voltage molded-case circuit breakers NEMA AB 1
Mechanical transport refrigeration units ARI 1 1 1 0
Packaged terminal air conditioners ARI 31 0/380
Positive displacement refrigerant compressor and compressor ANSI/ARI 520
units ANSI/ARI 540

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ANSI C84.1 -201 6
Page 1 2
Equipment Standard
Power switchgear
Automatic circuit reclosers
Automatic line sectionalizers
Capacitor switches
Distribution current-limiting fuses
Distribution cutout and fuse links
Distribution enclosed single-pole air switches
Distribution oil cutouts and fuse links ANSI C37 Series
Fused disconnecting switches
High-voltage air switches
Manual and automatic station control
Power circuit breakers
Power fuses
Relays and relay systems
Supervisory and associated telemetering equipment
Switchgear assemblies including metal enclosed bus
Reciprocating water-chilling packages ANSI/ARI 550
ANSI/ARI 590
Remote mechanical draft air-cooled refrigerant condensers ARI 460
Room air conditioners ANSI/AHAM RAC-1
Room fan-coil airs ARI 440
Rotating electrical machinery
AC induction motors
Cylindrical rotor synchronous generators ANSI C50 Series
Salient pole synchronous generator and condensers NEMA MG1
Synchronous motors
Universal motors
Central system humidifiers ANSI/ARI 620
Self-contained mechanically refrigerated drinking-water coolers ANSI/ARI 1 01 0
Shunt power capacitors ANSI/IEEE 1 8
Solenoid valves for liquid and gaseous flow ARI 760
Static power conversion equipment ANSI C34
Surge arresters ANSI/IEEE C62.2
ANSI/IEEE C62.21
NEMA LA1
Transformers, regulators, and reactors
Arc furnace transformers
Constant-current transformers
Current-limiting reactors
Distribution transformers, conventional subway-type
Dry type ANSI/IEEE C57 Series
Instrument transformers ANSI/NEMA ST20
Power transformers
Rectifier transformers
Secondary network transformers
Specialty
Step-voltage and induction-voltage regulators
Three-phase load-tap-changing transformers
Unit ventilators ARI 840
Unitary air-conditioning and air-source heat pump equipment ARI 21 0/240
Commercial and industrial unitary air-conditioning equipment ARI 340/360
Wiring devices ANSI C73 Series
*See list of organizations in Section D2.

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D.2 Organizations Referred to in Section D.1
AEIC Association of Edison Illuminating Companies
P.O. Box 2641
Birmingham, AL 35291
AHAM Association of Home Appliance Manufacturers
1 1 1 1 1 9th 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
25 West 43rd Street, 4th Floor
New York, NY 1 0036
ARI Air Conditioning and Refrigeration Institute
(Air-Conditioning, Heating, and Refrigeration Institute)
41 00 N. Fairfax Drive; Suite 200
Arlington, VA 22203
HI Hydronics Institute
Division of GAMA Gas Appliance Manufacturers Association
21 07 Wilson Blvd.
Arlington, VA 22201 -3042
IEEE The Institute of Electrical and Electronics Engineers, Inc.
445 Hoes Lane
Piscataway, NJ 08855
ICEA Insulated Cable Engineers Association
PO Box 1 568
Carrollton, GA 301 1 2
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NEMA National Electrical Manufacturers Association
1 300 North 1 7th Street; Suite 900
Rosslyn, VA 22209
NFPA National Fire Protection Association
1 Batterymarch Park
Quincy, MA 021 69-7471

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