A AS arent tein STANDARDS COLLECTION™ | Std 3004.1"-2013 SSM rola sale Marlee Colm Ut Application of Instrument Transformers in Industrial and Commercial Power Systems IEEE STANDARDS ASSOCIATION Cala‘Authorized icensed use limited to: UNIVERSIDAD DE GUANA,LIATO. Downloatied on February 102020 at 17:16:34 UTC trom IEEE Xplore. Restictons apelyIEEE Std 30041-2013, IEEE Recommended Practice for the Application of Instrument Transformers in Industrial and Commercial Power Systems Sponsor Technical Books Coordinating Committee of the IEEE Industry Applications Society Approved 6 February 2013 IEEE-SA Standards Board Approved 31 October 2014 American National Standards Institute ‘Autherized bcensed use lnted fo: UNIVERSIDAD DE GUANAJUATO Downloaded on February 10,2020 at 17 16:34 Crom IEEE Xplore. Restictons apy.Abstract: The selection and application of instrument transformers used in industrial and commercial power systems are covered in this recommended practice. Keywords: CT, current transformer, IEEE 3004.1”, instrument transformer, voltage transformer, VT The Insitute of Elecical and Elecrones Engineers, ne: 2 Park Avenue, Now Yar NY 100166007, USA ‘copyright © 2010 by The Insite of Elecincal and Electronics Engineers, ne [Alngpts reserved Pubished 6 Nay 2078 Pinta inthe Unied Sts of Americ, IEEE Isa relsteesademarkinine US. Patent & Trademark Ofte, owned by The Irsnue of Electreal and Eleevones Engneets neorarntes POF ISENG7eOTO=I-A7a1.5 —sTDBBTAO Pom: ISBNGTOLITS=I-82%2-2 — STDPDSETAD IEEE wonos dsoxmaaton nasser. ra Duta Fo mae eons Ws zt fi par ors paeston maybe repose yf an acre reneval je or Pence not epi waten amasion ofthe zubisher ‘Authorized icensed use limited to: UNIVERSIDAD DE GUANA,LIATO. Downloatied on February 102020 at 17:16:34 UTC trom IEEE Xplore. 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Restictons apelyParticipants At the time this IEEE recommended practice was completed, the Protection & Coordination Working Group had the following membership: Rasheek Rifaat, Chair Douald McCullough I Vice Chair Ray Clare Robert Hoeraut Daniel Neeser Dea Colaberandino Ed Lasoa Prafulla Pillai Carey Cook Claudio Mardegen Louie Powell Gary Fox (Cimeke Mazina ‘Marcelo Valdes With assistance fiom editorial Sub-Work Group including Louie Powell, Chair ‘The following members of the individual balloting conmnittee voted on this recommended practice, Balloters may have voted for approval, disapproval, or abstention, William Ackerman ‘Werner Hoetzl Sergio A. Paneta AU: AL Aviazi Robert Hoeraut Howard Penrose ‘Kennets Behrenst Gary Hoftinan Charles Perry Wallace Binder Gerald Johnson (Christopher Betola ‘Thomas Bishop ohn Kay Louie Powell William Bloethe Gael Kennedy Iulian Profi (Chris Brooks ‘Yuri Khersonsky ‘Michael Roberts Gustavo Brunello Boris Kogan (Charles Rogers William Byrd Jim Kulehisky Steven Sano Reith Chow ‘Saumen Kundo ‘Vincent Saporta Stephen Conrad Ed Larsen Bartien Sayoz0 ‘Tey Conrad Weivlen Lee Robert Schuerger Carey Cook Duane Lesehier Robert Seitz Thomas Domitrovich Greg Lust Gil Shultz Randall Dotson ‘Wayne Manges James Smith Neal Dowling Gary Michel Jeremy Smith (Gary Engmann ‘T.David Malls Jerry Smith Keith Flowers Jeny Murphy ‘Allan St. Peter Gary Fox. Daniel Neeser eter Sutherland (Cari Fredericks Dennis Neitzel David Tepen ‘Manjinder Gill Arthur Neubauer S. Thamilarasan David Gilmer ‘Michael S. Newman Demetrios Taiouvaras Randall Groves Joe Nims ‘Marcelo Valdes Paul Hamer Token John Wang Scott Hictpas Lorraine Paden sian Ya Wiien the IEEE-SA Standards Board approved this recommended practice on 6 February 2013, it had the following membership: John Kulick, Chair Richard H. Hulett, Past Char Konstantinos Karachalios, Secretary ‘Masayuki Asyoshi Stephen Dukes aul Houzé Peter Bama Jean-Philippe Faure sim Hughes Farooq Bari ‘Alexander Gelman, ‘Michael Fanezic ‘Ted Buse Mark Halpin Joseph L. Koepfinges* ‘Wael William Diab Gary Hoftinan David J. Law Copyright © 2013 IEEE. Al rights reserved. ‘Authorized icensed use limited to: UNIVERSIDAD DE GUANA,LIATO. Downloatied on February 102020 at 17:16:34 UTC trom IEEE Xplore. Restictons apelyOleg Logvinov Jon Walter Rosdahl Yatia Trivedi Ron Petersen ‘Adtian Stephens Phil Winston Gary Robinson Peter Sutherland Yu Yuan Member Emeritus Also inchuded are the following nonvoting IEEE-SA Standards Board liaisons: Richard DeBlasio, DOE Representative “Michael Janeze, IST Representative Julie Alessi IEEE Standards Program Manager. Document Development Lisa Perry IEEE Standards Program Mager, Technical Program Development Copyright® 2013 IEEE. Al ights esorvod ‘Authorized icensed use limited to: UNIVERSIDAD DE GUANA,LIATO. Downloatied on February 102020 at 17:16:34 UTC trom IEEE Xplore. Restictons apelyIntroduction “This iniroduction isnot part of IEEE Sid 30041-2013, IEEE Recommended Practice for the Application of Instrument “Transformers in Industrial and Commercial Power Systems. TH IEEE 3000 Standards Collection’ ‘This recommended practice was developed by the Technical Books Coordinating Committee of the Industrial and Commercial Power Systems Department of the Industry Applications Society as part of a project fo repackage the popular IEEE Color Books®. The goal of this project is to speed up the revision process eliminate duplicate material, and facilitate use of modem publishing and distribution tecluologics. When this project is completed, the technical material in the thirteen IEEE Color Books will be included in a series of new standards—the most significant of which will be a new standard, IEEE Std 3000"™, IEEE Recommended Practice for the Engineering of Industrial and Commercial Power Systems. The new standard will cover the fundamentals of planning, design, analysis, construction, installation, startup, ‘operation, and maintenance of electrical systems in industrial and commercial facilities. Approximately 60 additional dot standards, organized into the following categories, will provide in-depth treatment of many of the topics introduced by IEEE Std 3000 — Power Systems Design (3001 series) — Power Systems Analysis (3002 series) — Power Systems Grounding (3003 series) — Protection and Coordination (3004 series) — Emergency, Standby Power, and Eneray Management Systems (3005 series) — Power Systems Reliability (3006 series) — Power Systems Maintenance, Operations, and Safety (3007 seties) In many cases, the material in a dot standard comes from a particular chapter of a particular IEEE Color ‘Book. In other cases, material from several IEEE Color Books has been combined into a new dot standard. 2™ (EEE Buff Book™ ‘The material inthis recommended practice largely comes from IEEE Std IEEE Std 3004.1™ This recommended practice covers the selection and application of instrument transfonuers used in industrial and commercial power systems. Copyright © 2013 IEEE. Al rights reserved. ‘Authorized icensed use limited to: UNIVERSIDAD DE GUANA,LIATO. Downloatied on February 102020 at 17:16:34 UTC trom IEEE Xplore. Restictons apelyContents 1. Overview 1.1 Scope. - Nonmnative references. 3. Definitions 4, Current transformers. 4.1 Equivalent cireuit for current transformers. 4.2 Burden. 4.3 Current transformer ratings and performance parameters 44 Accuracy ratings. 4.5 Current transformer voltage and BIL ratings, 466 Unuswal service conditions 4.7 Current transformer construction. 4.8 Current transformer connections 4.9 Current transformer application guide.. 5. Voltage (potential) transformers. 5.1 Funetional definition, 5.2 Voltage transformer performance... 533 Voltage transformer ratings and performance parameters. Ea $44 Voltage transformer construction. : co BL 5.5 Voltage transformer comestions 32 5.6 Voltage transformer application guide co ‘Annex A (informative) Bibliography 36 Copyright® 2013 IEEE. Al ights resorved. ‘Authorized icensed use limited to: UNIVERSIDAD DE GUANA,LIATO. Downloatied on February 102020 at 17:16:34 UTC trom IEEE Xplore. Restictons apely‘Authorized icensed use limited to: UNIVERSIDAD DE GUANA,LIATO. Downloatied on February 102020 at 17:16:34 UTC trom IEEE Xplore. Restictons apelyIEEE Recommended Practice for the Application of Instrument Transformers in Industrial and Commercial Power Systems IMPORTANT NOTICE: IEEE Standards documents are not intended to ensure safety, health, or ‘environmental protection, or ensure against interference with or from other devices or networks. Inplementers of IEEE Standards documents are responsible for determining and complying with all ‘appropriate safety, security, environmental, health, and interference protection practices and all ‘applicable laws and regulations. This IEEE document is made available for use subject to important notices and legat disclaimers These notices and disclaimers appear in all publications containing this document and may be found under the heading “Important Notice” or “Important Notices and Disclaimers Concerning IEEE Documents.” They can also be obtained on request from IEEE or viewed at Inip:/standards.jeve.org/IPR/disclaimers. html. 1. Overview 1.4 Scope This recommended practice covers the selection and application of instrument transformers used in industrial and commercial power systems. 2. Normative references The following referenced documents are indispensable for the application of this document (ie. they must be understood and used, so each referenced document is cited in text and its relationship to this document is explained), For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments or corrizenda) applic. 1 Copyright © 2013 IEEE. Al rights reserved. ‘Autherized bcensed use linted fo: UNIVERSIDAD DE GUANAJUATO. Downloaded on February 10,2020 at 1716.34 UTC trom IEEE Xolore. Restictions applyIFEE std 3004 1.2013 EEE Rocommonded Prati fr the Applicaton of lnstument Transformers in Industial and Commercial Power Systems IEEE Std C57.13™, IEEE Standard Requirements for Instrument Transformers'? IEEE Std C57.13.3™, IBEE Guide for Grounding of Instrument Transformer Secondary Circuits and Cases IEEE Std C57.13.6™, IEEE Standard for High-Accuracy Instrument Transformers TEC Std 60044-1™, Instrument Transformers: Part I—Curtent Transformers? IEC Std 60044-2™. Instrument Transformers: Part 2—Inductive Voltage Transformers 3. Definitions For the purposes of this document, the following terms and definitions apply. The IEEE Standards Dictionary Online should be consulted for terms not defined in this clause.* burden: The load connected to the secondary terminals, which may be expressed as voltamperes and power factor at a specified value of current, total ohms impedance and power factor, or ohms of the resistance and reactive components, composite error: The root-mean-square (rns) of the instantaneous difference between the actual primary curent and the actual secondary current multiplied by the rated current transformer transformation error. current transformer (CT): Transforms line current into values suitable for use with standard protective relays and meters while isolating these instruments from line voltages. dynamic current rating (Ljyq): The crest value of the asymmetrical primary current which a current ‘wansformer must withstand without being damaged electrically or mechanically by the resulting electromagnetic forces with the secondary winding short-circuited. knee-point voltage: (A) The voltage at which a line tangent to the secondary excitation characteristic, ‘when drawn on log-log coordinates. is at an angle of 45° to the horizontal. (B) The rated-frequency secondary voltage abave which a 10% increase in voltage results in an increase af 5 ‘current. (adapted fiom IEC) polarity: The instantaneons phase relationship between the currents flowing in the primary and secondary of a current transformer. In simple applications, polarity is not important, but itis a critical consideration ‘whenever multiple curent transformers are used in combination, or when the output of a cuent transformer is used in conjunction with the output of a voltage transformer. rating: The rating of a current transformer consists ofa primary current rating and an associated secondary current rating. These ratings are related by the nominal transformation ratio of the current transformer, ‘which is usually also the physical tums ratio of the transformer. ratio correction factor (RCF): The ratio of the true, or measured, ratio of the current transformer to the ‘marked, or nominal, ratio. "The IEEE otandands or product refered to in hs clauee are trademarks of The Insite of Elctricel and Electronics Enginces, Le. + IEEE publications are avaiable ftom The latte of Elecieal and Electonics Engineer, 445 Hos Lane Pucaaway, NY 08854, {USA Git tad cong. “IEC pubotone ae svalble om th Sales Depart of th ltemaionl Elesuotechnicel Comision, 3 re de Vaombé, PO ‘Box 131, CH-IZ1, Geneva 2, Switzerland Gi ec ch). TEC publications are also available nthe United Sttes from te Sales Departmant, American National Standards asi, 25 Wat 43rd Stet 4th Floor, New York, NY 10036,U8A, (itp: www asin). NIEEE Standards Dictionary Online sbsrigtion i avilable a ‘np sore or portal innovate products stander standards dictionary hi. 2 Copyright © 2013 IEEE. Al rights reserved. ‘Authorized icensed use limited to: UNIVERSIDAD DE GUANA,LIATO. Downloatied on February 102020 at 17:16:34 UTC trom IEEE Xplore. Restictons apelyIFEE std 3004 1.2013 EEE Rocommonded Prati fr the Applicaton of lnstument Transformers in Industial and Commercial Power Systems ratio error: The degree to which the ratio correction factor deviates from the ideal, or textbook case, and is typically expressed in percent, short-time thermal current rating: The maximum current that the cuent tansformer can carry for a specified period of ime. transformer correction factor (TCF): Takes into account both the magnitude of error and any associated error in phase angle. TCF tends to be more of a concern in metering applications and is the factor by which the reading of a wattmeter may be adjusted to compensate for inaccuracies. voltage transformer (VT): Transforms line voltage into values suitable for standard protective relays and ‘meters while isolating these instruments from the stresses associated with the primary power system, 4. Current transformers A current transformer (CT) transforms line current into values suitable for use with standard protective relays and meters while isolating these instruments fiom line voltages. A typical CT has two windings, designated as primary and secondary, which are insulated from each other. Most CTs are conventional in the sense that they are transformers consisting of winding on iron cores. However, air core CTs have been used in power system applications, and CTs utilizing optical technology are becoming available. The primary winding is connected in series with the circuit carrying the line cwrent to be measured: and the seconciary winding is connected to protective devices, instruments, meters, or control devices, Ideally, CTs change the magnitude of the cutent being measured without changing the phase angle or ‘wave shape of the current. Practically, however. the output of CTs does contain some error and distortion, ‘and dealing with these errors and distortion is one of the primary challenges in applying CTS. uit for current transformers To understand the performance and application of CTs, it is necessary to start with an equivalent citewit, The circuit shown in Figure 1 is representative, although variations on this circuit may be found in various texts tpi Rejol ts ccm Figure 1—Equivalent circuit for a CT In this equivalent circuit - is the primary system current L is the secondary current fed to the meters or relays N is the nominal turns ratio of the CT RejoL is the impedance of the CT secondary winding and leads, and the secondary witing to the Joads (meters or relays) applied tothe CT 3 Copyright © 2013 IEEE. Al ights reserved. ‘Authorized icensed use limited to: UNIVERSIDAD DE GUANA,LIATO. Downloatied on February 102020 at 17:16:34 UTC trom IEEE Xplore. Restictons apelyIFEE std 3004 1.2013 EEE Rocommonded Prati fr the Applicaton of lnstument Transformers in Industial and Commercial Power Systems Zs is the impedance of the load (meters or relays) ve is the voltage across the CT secondary kL is the exciting current drawn by the iron core of the CT ‘There are several important relationships depicted in this equivalent citeuit. Fist, the secondary current produced by the CT is not equal to the primary current, divided by the CT tums ratio. Instead, there is an esror due to the need to supply exciting current to the CT cose. This relationship can be expressed algebraically as bs = Secondly, the secondary voltage, V., is a function of the secondary current and the total secondary burden impedance, including both external elements (the impedances of meters, relays, and interconnecting wiring) and the intemal impedance of the CT secondary winding. a) Ws= [+R+jol] Q) ‘The third important relationship is that the exciting current, Ia is a function of the CT secondary voltage, Vj. However, this is uot a linear relationship, but rather is defined by a curve, called the CT secondary excitation characteristic, that represents the nou-linear behavior of the iton core of the CT. Figure 2 depicts an idealized CT secondary excitation characteristic. Typically. the excitation characteristics are plotted on log-log paper. Therefore, even though some portions of the curve appear to be linear (ie.. a straight line), the relationship is actually non-linear. Vs le Figure 2—Idealized CT secondary excitation characteristic The secondary excitation characteristic is derived from the hysteresis characteristic of the ferrous core of the CT. As V, becomes large. there comes a point when the CT essentially becomes unable to sustain further increases in V.. Referring to the equivalent circuit, further increases in IyN translate almost completely to increases in exciting current L, At that point, the CT is said to be saturated. Practical secondary excitation characteristics are usually published by CT manufacturers in the form of excitation cumrent versus secondary mus voltage. The values are obtained either by calculation from ‘wansformer design and cose-loss data or by testing a representative sample of the CTs produced by the ‘manufieturer, The test is an open-cireuit excitation current test on the secondary tenminals, applying @ variable sine wave voltage at rated frequency and recording ms current versus rms Voltage. ‘A tern that frequently appears in the technical literature is knee-point voltage. This is the voltage at the inflection point of the curve of V, versus I (Figure 2). The working definition of knee-point voltage under 4 Copyright © 2013 IEEE. Al rights reserved. ‘Authorized icensed use limited to: UNIVERSIDAD DE GUANA,LIATO. Downloatied on February 102020 at 17:16:34 UTC trom IEEE Xplore. Restictons apely