ANSI C Consensus does not necessarily mean that there is unanimous agreement among every person participating in the development of this document. NEMA standards and guideline publications, of which the document contained herein is one, are developed through a voluntary consensus standards development process. While NEMA administers the process and establishes rules to promote fairness in the development of consensus, it does not write the document and it does not independently test, evaluate, or verify the accuracy or completeness of any information or the soundness of any judgments contained in its standards and guideline publications. NEMA disclaims liability for any personal injury, property, or other damages of any nature whatsoever, whether special, indirect, consequential, or compensatory, directly or indirectly resulting from the publication, use of, application, or reliance on this document.
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ANSI C Consensus does not necessarily mean that there is unanimous agreement among every person participating in the development of this document. NEMA standards and guideline publications, of which the document contained herein is one, are developed through a voluntary consensus standards development process.
While NEMA administers the process and establishes rules to promote fairness in the development of consensus, it does not write the document and it does not independently test, evaluate, or verify the accuracy or completeness of any information or the soundness of any judgments contained in its standards and guideline publications. NEMA disclaims liability for any personal injury, property, or other damages of any nature whatsoever, whether special, indirect, consequential, or compensatory, directly or indirectly resulting from the publication, use of, application, or reliance on this document.
NEMA disclaims and makes no guaranty or warranty, express or implied, as to the accuracy or completeness of any information published herein, and disclaims and makes no warranty that the information in this document will fulfill any of your particular purposes or needs.
In publishing and making this document available, NEMA is not undertaking to render professional or other services for or on behalf of any person or entity, nor is NEMA undertaking to perform any duty owed by any person or entity to someone else.
Anyone using this document should rely on his or her own independent judgment or, as appropriate, seek the advice of a competent professional in determining the exercise of reasonable care in any given circumstances. Information and other standards on the topic covered by this publication may be available from other sources, which the user may wish to consult for additional views or information not covered by this publication.
NEMA has no power, nor does it undertake to police or enforce compliance with the contents of this document. NEMA does not certify, test, or inspect products, designs, or installations for safety or health purposes. Any certification or other statement of compliance with any health or safety—related information in this document shall not be attributable to NEMA and is solely the responsibility of the certifier or maker of the statement.
Consensus is established when, in the judgment of the ANSI Board of Standards Review, substantial agreement has been reached by directly and materially affected interests. Substantial agreement means much more than a simple majority, but not necessarily unanimity. Consensus requires that all views and objections be considered, and that a concerted effort be made toward their resolution.
The use of American National Standards is completely voluntary; their existence does not in any respect preclude anyone, whether he has approved the standards or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not conforming to the standards.
The American National Standards Institute does not develop standards and will in no circumstances give an interpretation of any American National Standard. Moreover, no person shall have the right or authority to issue an interpretation of an American National Standard in the name of the American National Standards Institute.
Requests for interpretations should be addressed to the secretariat or sponsor whose name appears on the title page of this standard. The procedures of the American National Standards Institute require that action be taken periodically to reaffirm, revise, or withdraw this standard. Purchasers of American National Standards may receive current information on all standards by calling or writing the American National Standards Institute.
No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher. Printed in the United States of America. Standard nominal system voltages and voltage ranges shown in the previous standard have been extended to include maximum system voltages of up to and including kV.
American National Standard C 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. 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.
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: 1 A comprehensive questionnaire on power system design and operating practices, including measurement of actual service voltages.
Approximately 65, 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. 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 C This resulted in the approval and publication of American National Standard C Suggestions for improvement of the standard will be welcome.
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 J. Saar Joel G. Solis Reuben F. Burch IV Albert J. Keri Frank Denbrock Daniel J. Ward, P. Larry E. Conrad Gregory T. Obenchain, P. Gail Royster Ed M. Yandek Peter Philips Michael C. Pehosh Robert D. Saint Ronald N.
Helms Howard L. Wolfman, P. Smullin Engineering, Inc. Synergetic Design Roger H. Daugherty T. Olsen Gary T. Smullin, P. James J. 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 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. Portions of the system may be under different ownership, such as that of a supplier or a user.
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. Each system voltage pertains to a portion of the system that is bounded by transformers or utilization equipment. 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.
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. 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.
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.
The occurrence of service voltages outside of these limits should be infrequent. Utilization equipment shall be designed and rated to give fully satisfactory performance throughout this range. 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. Utilization equipment may not operate satisfactorily under these conditions, and protective devices may operate to protect the equipment.
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. 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 to Caution should be exercised in applying the Range B minimum voltages of table 1 and note 1 to existing volt systems supplying such motors.
The source may be derived from any type of threephase 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.
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. Maximum utilization voltages would not be expected to exceed volts for the nominal system voltage of , nor appropriate multiples thereof for other nominal system voltages through volts.
For equipment supplied through transformers, refer to limits for nominal system voltage of transformer output. Systems of more than volts are normally three-phase and supplied by connections 3 , 5 ungrounded, or 7. Systems of 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.
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. 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 volt base. See note 1 to table 1. See note c to table 1. This difference is greater for service at more than volts to allow for additional voltage drop in transformations between service voltage and utilization equipment.
ANSI C However, it does not include momentary disturbances, which may be the result of, but not limited to, utility switching operations, large motor starts, lightning strikes, fault clearing and similar occurrences. Basically, the standard stated the following objectives: 1. Promote a better understanding of the voltages associated with power systems and utilization equipment to achieve overall practical and economical design and operation. 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.
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