Bsi bs en 61869 6 2016

BS EN 61869-6:2016 BSI Standards Publication Instrument transformers Part 6: Additional general requirements for low-power instrument transformers BRITISH STANDARD BS EN 61869-6:2016 National foreword This British Standard is the UK implementation of EN 61869-6:2016 It is identical to IEC 61869-6:2016 It supersedes BS EN 60044-7:2000, which will be withdrawn on 23 December 2019 and, together with BS EN 61869-9 (in preparation), it supersedes BS EN 60044-8:2002, which will be withdrawn upon the publication of BS EN 61869-9 The UK participation in its preparation was entrusted to Technical Committee PEL/38, Instrument transformers A list of organizations represented on this committee can be obtained on request to its secretary This publication does not purport to include all the necessary provisions of a contract Users are responsible for its correct application © The British Standards Institution 2017 Published by BSI Standards Limited 2017 ISBN 978 580 79869 ICS 17.220.20 Compliance with a British Standard cannot confer immunity from legal obligations This British Standard was published under the authority of the Standards Policy and Strategy Committee on 28 February 2017 Amendments/corrigenda issued since publication Date Text affected BS EN 61869-6:2016 EUROPEAN STANDARD EN 61869-6 NORME EUROPÉENNE EUROPÄISCHE NORM December 2016 ICS 17.220.20 Supersedes EN 60044-7:2000 (partially), EN 60044-8:2002 (partially) English Version Instrument transformers - Part 6: Additional general requirements for low-power instrument transformers (IEC 61869-6:2016) Transformateurs de mesure - Partie 6: Exigences générales supplémentaires concernant les transformateurs de mesure de faible puissance (IEC 61869-6:2016) Messwandler - Teil 6: Zusätzliche allgemeine Anforderungen für Kleinsignal-Messwandler (IEC 61869-6:2016) This European Standard was approved by CENELEC on 2016-06-01 CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CENELEC member This European Standard exists in three official versions (English, French, German) A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom European Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische Normung CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels © 2016 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members Ref No EN 61869-6:2016 E BS EN 61869-6:2016 EN 61869-6:2016 European foreword The text of document 38/501/FDIS, future edition of IEC 61869-6, prepared by IEC/TC 38 "Instrument transformers" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as EN 61869-6:2016 The following dates are fixed: • latest date by which the document has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2017-06-23 • latest date by which the national standards conflicting with the document have to be withdrawn (dow) 2019-12-23 This document is to be read jointly with, and is based on, EN 61869-1:2009, General requirements, However, the reader is encouraged to use the most recent edition of that document This document follows the structure of EN 61869 series and supplements or modifies the corresponding clauses in EN 61869-1 Standard When a particular clause/subclause of Part 1, is not mentioned in this Part 6, that clause/subclause applies as far as is reasonable When this standard states “addition”, “modification” or “replacement”, the relevant text in Part is to be adapted accordingly For additional clauses, subclauses, figures, tables, annexes or notes, the following numbering system is used: – clauses, subclauses, tables, figures and notes that are numbered starting from 601 are additional to those in Part 1; – additional annexes are lettered 6A, 6B, etc This document, jointly with EN 61869-1:2009, supersedes EN 60044-7:2000 (partially) and EN 60044-8:2002 (partially) Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights CENELEC [and/or CEN] shall not be held responsible for identifying any or all such patent rights Endorsement notice The text of the International Standard IEC 61869-6:2016 was approved by CENELEC as a European Standard without any modification In the official version, for Bibliography, the following notes have to be added for the standards indicated: IEC 60044-7:1999 NOTE Harmonized as EN 60044-7:2000 (not modified) IEC 60044-8:2002 NOTE Harmonized as EN 60044-8:2002 (not modified) IEC 61508-1 NOTE Harmonized as EN 61508-1 IEC 61508-3 NOTE Harmonized as EN 61508-3 IEC 61850 Series NOTE Harmonized as EN 61850 Series IEC 61869 Series NOTE Harmonized as EN 61869 Series IEC 61869-5 NOTE Harmonized as EN 61869-5 IEC 61869-9 NOTE Harmonized as EN 61869-9 IEC 61869-10 NOTE Harmonized as EN 61869-10 IEC 61869-11 NOTE Harmonized as EN 61869-11 BS EN 61869-6:2016 EN 61869-6:2016 Annex ZA (normative) Normative references to international publications with their corresponding European publications The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application For dated references, only the edition cited applies For undated references, the latest edition of the referenced document (including any amendments) applies NOTE When an International Publication has been modified by common modifications, indicated by (mod), the relevant EN/HD applies NOTE Up-to-date information on the latest versions of the European Standards listed in this annex is available here: www.cenelec.eu Annex ZA of EN 61869:2009 is applicable with the following additions: Publication Year Title EN/HD Year - - Voltage characteristics of electricity supplied by public electricity networks EN 50160 2010 IEC 60068-2-6 2007 Environmental testing Part 2-6: Tests - Test Fc: Vibration (sinusoidal) EN 60068-2-6 2008 IEC 60255-27 2013 Measuring relays and protection equipment EN 60255-27 - Part 27: Product safety requirements 2014 IEC 60603-7-1 2011 Connectors for electronic equipment Part 7-1: Detail specification for 8-way, shielded, free and fixed connectors EN 60603-7-1 2011 IEC 60794-2 2002 Optical fibre cables Part 2: Indoor cables - Sectional specification EN 60794-2 2003 IEC 60794-3 2014 Optical fibre cables Part 3: Outdoor cables - Sectional specification EN 60794-3 2015 IEC 60812 2006 Analysis techniques for system reliability - EN 60812 Procedure for failure mode and effects analysis (FMEA) 2006 IEC 61000-4-1 2006 Electromagnetic compatibility (EMC) Part 4-1: Testing and measurement techniques - Overview of IEC 61000-4 series EN 61000-4-1 2007 IEC 61000-4-2 2008 Electromagnetic compatibility (EMC) Part 4-2: Testing and measurement techniques - Electrostatic discharge immunity test EN 61000-4-2 2009 IEC 61000-4-3 2006 EN 61000-4-3 2006 +A1 +A2 2007 2010 Electromagnetic compatibility (EMC) Part 4-3: Testing and measurement techniques - Radiated, radio-frequency, electromagnetic field immunity test +A1 +A2 2008 2010 1) 2) 1) 2) Superseded by IEC/TR 61000-4-1:2016 Withdrawn publication BS EN 61869-6:2016 EN 61869-6:2016 Publication Year Title IEC 61000-4-4 2012 Electromagnetic compatibility (EMC) EN 61000-4-4 Part 4-4: Testing and measurement techniques - Electrical fast transient/burst immunity test 2012 IEC 61000-4-5 2014 Electromagnetic compatibility (EMC) Part 4-5: Testing and measurement techniques - Surge immunity test EN 61000-4-5 2014 IEC 61000-4-6 2013 Electromagnetic compatibility (EMC) EN 61000-4-6 Part 4-6: Testing and measurement techniques - Immunity to conducted disturbances, induced by radio-frequency fields 2014 IEC 61000-4-7 2002 2002 +A1 2008 Electromagnetic compatibility (EMC) EN 61000-4-7 Part 4-7: Testing and measurement techniques - General guide on harmonics and interharmonics measurements and instrumentation, for power supply systems and equipment connected thereto +A1 IEC 61000-4-8 2009 Electromagnetic compatibility (EMC) Part 4-8: Testing and measurement techniques - Power frequency magnetic field immunity test EN 61000-4-8 2010 IEC 61000-4-9 1993 1993 3) +A1 2000 Electromagnetic compatibility (EMC) EN 61000-4-9 Part 4-9: Testing and measurement techniques - Pulse magnetic field immunity test +A1 2001 3) IEC 61000-4-10 1993 1993 +A1 2000 Electromagnetic compatibility (EMC) EN 61000-4-10 Part 4-10: Testing and measurement techniques - Damped oscillatory magnetic field immunity test +A1 IEC 61000-4-11 2004 Electromagnetic compatibility (EMC) Part 4-11: Testing and measurement techniques - Voltage dips, short interruptions and voltage variations immunity tests EN 61000-4-11 2004 IEC 61000-4-13 2002 2002 +A1 2009 Electromagnetic compatibility (EMC) EN 61000-4-13 Part 4-13: Testing and measurement techniques - Harmonics and interharmonics including mains signaling at a.c power port, low frequency immunity tests +A1 3) 4) 4) EN/HD Superseded by EN 61000-4-9:2016 (IEC 61000-4-9:2016): DOW = 2019-08-17 Superseded by IEC 61000-4-10:2016 Year 2009 2001 2009 BS EN 61869-6:2016 EN 61869-6:2016 Publication Year Title IEC 61000-4-16 1998 +A1 +A2 2001 2009 Electromagnetic compatibility (EMC) EN 61000-4-16 Part 4-16: Testing and measurement techniques - Test for immunity to conducted, common mode disturbances in the frequency range Hz to 150 kHz +A1 +A2 IEC 61000-4-18 2006 +A1 2010 IEC 61000-4-29 2000 Electromagnetic compatibility (EMC) EN 61000-4-29 Part 4-29: Testing and measurement techniques - Voltage dips, short interruptions and voltage variations on d.c input power port immunity tests 2000 IEC 61025 2006 Fault Tree Analysis (FTA) EN 61025 2007 IEC 61076-2-101 2012 Connectors for electronic equipment Product requirements Part 2-101: Circular connectors - Detail specification for M12 connectors with screw-locking EN 61076-2-101 2012 IEC/TS 61850-2 2003 Communication networks and systems in substations Part 2: Glossary - - IEC 61850-7-4 2010 Communication networks and systems for EN 61850-7-4 power utility automation Part 7-4: Basic communication structure Compatible logical node classes and data object classes 2010 IEC 61869-1 (mod) 2007 Instrument transformers Part 1: General requirements EN 61869-1 2009 IEC 61869-2 2012 Instrument transformers EN 61869-2 Part 2: Additional requirements for current transformers 2012 IEC 61869-3 2011 Instrument transformers Part 3: Additional requirements for inductive voltage transformers EN 61869-3 2011 IEC/TR 61869-103 2012 Instrument transformers - The use of instrument transformers for power quality measurement - - IEC 62271-100 2008 2009 +A1 2012 High-voltage switchgear and controlgear - EN 62271-100 Part 100: Alternating current circuitbreakers +A1 CISPR 11 (mod) 2015 Industrial, scientific and medical equipment EN 55011 - Radio-frequency disturbance characteristics - Limits and methods of measurement 2016 5) Electromagnetic compatibility (EMC) Part 4-18: Testing and measurement techniques - Damped oscillatory wave immunity test EN/HD Year 1998 5) 2004 2011 EN 61000-4-18 2007 + corr September 2007 +A1 2010 2012 Superseded by EN 61000-4-16:2016 (IEC 61000-4-16:2015): DOW = 2019-01-13 BS EN 61869-6:2016 EN 61869-6:2016 Publication Year Title ISO/IEC/IEEE 21451-4 2010 Information technology - Smart transducer interface for sensors and actuators Part 4: Mixed-mode communication protocols and Transducer Electronic Data Sheet (TEDS) formats EN/HD Year - BS EN 61869-6:2016 –2– IEC 61869-6:2016  IEC 2016 CONTENTS FOREWORD Scope 10 Normative reference 10 Terms and definitions 13 3.1 General terms and definitions 13 3.2 Terms and definitions related to dielectric ratings and voltages 17 3.3 Terms and definitions related to current ratings 17 3.4 Terms and definitions related to accuracy 21 3.5 Terms and definitions related to other ratings 26 3.7 Index of abbreviations and symbols 26 Normal and special service conditions 28 4.2 Normal service conditions 28 4.2.3 Vibrations or earth tremors 28 4.2.601 Partially outdoor LPIT 28 Ratings 28 5.3 Rated insulation levels and voltages 28 5.3.5 Insulation requirements for secondary terminals 28 5.3.601 Rated auxiliary power supply voltage (U ar ) 28 5.4 Rated frequency 29 5.5 Rated output 29 5.5.601 Rated burden (R br ) 29 5.5.602 Standard values for the rated delay time (t dr ) 29 5.6 Rated accuracy class 30 Design and construction 30 6.7 Mechanical requirements 30 6.11 Electromagnetic compatibility (EMC) 30 6.11.3 Requirements for immunity 30 6.11.4 Requirement for transmitted overvoltages 32 6.11.601 Emission requirements 32 6.13 Markings 33 6.601 Requirements for optical transmitting system and optical output link 33 6.601.1 General 33 6.601.2 Optical connectors 33 6.601.3 Fibre optic terminal box 33 6.601.4 Total cable length 33 6.602 Requirements for electrical transmitting system and electrical wires for output link 33 6.602.1 Connectors 33 6.602.2 Earthing of the output cable 34 6.603 Signal-to-noise ratio 34 6.604 Failure detection and maintenance announcement 35 6.605 Operability 35 6.606 Reliability and dependability 35 6.607 Vibrations 35 Tests 36 7.1 General 36 BS EN 61869-6:2016 IEC 61869-6:2016  IEC 2016 –3– 7.1.2 List of tests 36 7.2 Type tests 37 7.2.1 General 37 7.2.2 Temperature-rise test 37 7.2.3 Impulse voltage withstand test on primary terminals 37 7.2.5 Electromagnetic compatibility (EMC) tests 37 7.2.6 Test for accuracy 41 7.2.601 Low-voltage component voltage withstand test 43 7.3 Routine tests 44 7.3.1 Power-frequency voltage withstand tests on primary terminals 44 7.3.4 Power-frequency voltage withstand tests on secondary terminals 45 7.3.5 Test for accuracy 45 7.3.601 Power-frequency voltage withstand test for low-voltage components 45 7.4 Special tests 45 7.4.601 Vibration tests 45 601 Information to be given with enquiries, tenders and orders 46 601.1 Designation 46 601.2 Dependability 46 Annex 6A (normative) LPIT frequency response and accuracy requirements for harmonics 47 6A.1 General 47 6A.2 Requirements for noise and distortion 47 6A.3 Anti-aliasing filter requirements for LPIT using digital data processing 47 6A.4 LPIT accuracy requirements for harmonics and low frequencies 49 6A.4.1 General 49 6A.4.2 Measuring accuracy classes 49 6A.4.3 Accuracy class extension for quality metering and low bandwidth d.c applications 50 6A.4.4 Protective accuracy classes 51 6A.4.5 Special high bandwidth protection accuracy class 51 6A.4.6 Special accuracy classes for d.c coupled low-power voltage transformers 52 6A.5 Tests for accuracy versus harmonics and low frequencies 52 6A.6 Test arrangement and test circuit 53 6A.6.1 Test for accuracy for harmonics and low frequencies 53 6A.6.2 Type test for proper anti-aliasing 53 Annex 6B (informative) Transient performances of low-power current transformers 55 6B.1 General 55 6B.2 Short-circuit currents in power systems 55 6B.3 Conventional current transformer equivalent circuit 58 6B.4 Types of current transformers 60 6B.4.1 Types of conventional CTs 60 6B.4.2 Types of low-power current transformers 61 6B.5 Transient performance of current transformers 62 6B.5.1 Transient performance of conventional current transformers 62 6B.5.2 Transient performance of low-power current transformers 63 6B.6 Summary 64 Annex 6C (informative) Transient performances of low-power voltage transformers 65 6C.1 Overview 65 BS EN 61869-6:2016 IEC 61869-6:2016  IEC 2016 6C.3.1.5 – 73 – Effects of transients on protective relays In high-voltage substations VTs are connected to protective relays The input stage of these relays is equipped with inductive magnetic VTs ensuring galvanic insulation These transformers are very small in size and their primary winding is made with very thin wires Consequently, they are very sensitive to the presence of any d.c component at their input This d.c component can induce a saturation of their magnetic circuits The resulting overcurrent can cause a thermal breakdown of the primary winding Care should be taken by the user and manufacturer to verify the effect of the electronic VT on the relays during the presence of trapped charges This is particularly important if the low-power voltage transformer has an output amplified to emulate conventional voltage transformers (above ±15 V peak) and is capable of transmitting direct voltage, or voltage at very low frequency 6C.3.2 Definition of transient error The instantaneous voltage error is defined by the following formula: ε (t ) % = u ⋅ us ( t ) u p ( t ) K− up 100 where ε u (t) % is the instantaneous voltage error; Kr is the rated transformation ratio 6C.3.3 Test of transient performance 6C.3.3.1 Transient performance test for capacitive voltage transformers In IEC 61869-5, CVTs are subject to transient performance requirements, the primary short circuit alone being taken into consideration The test can be done by recording two signals The first is the output of the CVT The second is the output of a reference device representing the primary voltage and giving an accurate determination of the instant at which the short circuit occurs The performance is simply controlled by direct measurement of the residual value of the first signal 6C.3.3.2 6C.3.3.2.1 Transient performance test for low-power voltage transformers General The instantaneous voltage error for transient conditions is defined by the following formula: ε (t ) % = u ⋅ us ( t ) u p ( t ) K− up 100 This formula can be rewritten as follows: ε K up (t ) r × 100  up r  ( t ) % = u (t )  s u K Using the steady-state error definition  BS EN 61869-6:2016 – 74 – ε %= u IEC 61869-6:2016  IEC 2016 Kr ⋅U - U s U p × 100 p U p can be expressed by a function of U s Up = K rU s + ε u 100 Replacing U p by this expression in the previous formula gives ε (1 + εu / 100) × 100 up (t )  us r  ( t ) % = u (t )  s u K  Taking into account that εu 100 Thus, the formula above becomes reduced to ε u %(t ) = u s (t ) Us × 100 which is the mathematical expression of the requirement expressed in this standard NOTE U s is the peak value of the low-power voltage transformers secondary output voltage for t < (before the short circuit occurs) This simplified formula makes use of a calibrated primary voltage reference for primary BS EN 61869-6:2016 IEC 61869-6:2016  IEC 2016 – 75 – short circuit testing unnecessary Only one time reference is needed to identify the precise moment at which the short circuit occurs 6C.3.3.2.3 Reclosure on a line with trapped charges For t < u p (t) = u p dc (t) + u p res (t) u s (t) = u s res (t) dc (t) + us For t > u p(t) = U p ⋅ sin(2π ⋅ f ⋅ t + ϕ p) + u p res(t) u s(t) = U s ⋅ sin(2π ⋅ f ⋅ t + ϕ s) + u s dc(t) + u s res(t) Then for t > ε u × 100 up (t )  us r (t ) % = us (t ) - K1  Replacing u s (t) and u p (t) by their expression, we get ε u %(t ) = ε u ac %(t ) + ε u tr %(t ) with ε u ac %(t ) = U s sin( 2p ⋅ f ⋅ t + ϕs ) − (U p K r ) sin( p f ⋅ t + ϕ p ) e u tr %(t ) = Us us dc (t ) + us res (t ) − (up res (t ) K r ) Us × 100 × 100 The first term ε utr %(t) contains only sinusoidal components and is the steady-state error of the low-power voltage transformer If the low-power voltage transformer is correctly adjusted, it can be neglected considering the second term ε utr %(t) which is the error's transient component The worst case is where up dc (0) = FVU s The time constant of the low-power voltage transformer component u sdc (t) has a substantial influence on the choice of a test procedure We shall distinguish two cases: long- and short time constants 6C.3.3.2.4 Short time constants If u sdc (t) decays with a time constant less than 100 ms, a realistic test arrangement is possible, as shown in Figure 6C.4 BS EN 61869-6:2016 – 76 – IEC 61869-6:2016  IEC 2016 CB1 CB2 e2 e1 ≈ Ref LPVT C Line u ref (t) u s (t) Diff u diff (t) = u ref (t) – u s (t) IEC Key Ref is a high-voltage reference divider with the same voltage ratio as the low-power voltage transformer Diff is a calibrated differential amplifier with a low pass bandwidth characteristic determined by an agreement between user and manufacturer Figure 6C.4 – Testing arrangement for short time constant e (t) is set to the rated voltage and frequency, e (t) is set to a d.c value equal to the rated peak value, multiplied by the overvoltage factor F V e = U pr sin(2π f t) e = k U pr C Line > 000 pF in order to ensure that the primary voltage decay is at least 10 times slower than the secondary voltage decay of the low-power voltage transformer during the trapped charge situation (CB1 and CB2 open) Sequence of operation: a) CB1 open CB2 closed Charging the high-voltage capacitors (C Line , low-power voltage transformer, etc.) up to the assigned value F V ⋅ U pr b) CB1 open CB2 open Isolating the high-voltage d.c source e from the a.c source e c) CB1 closed CB2 open Reclosing on trapped charges with a rated value U pn for the a.c component 6C.3.3.2.5 Long time constants If u s dc (t) decays with a time constant higher than 100 ms, a realistic test arrangement is possible, as shown in Figure 6C.5 BS EN 61869-6:2016 IEC 61869-6:2016  IEC 2016 – 77 – Rg ≈ Ref LPVT e (t) u s (t) u ref (t) Diff u diff (t) = u ref (t) – u s (t) IEC Key Ref represents a high-voltage reference divider with the same voltage ratio as the low-power voltage transformer Diff represents a calibrated differential amplifier with a low-pass bandwidth characteristic determined by an agreement between user and manufacturer Figure 6C.5 – Testing arrangement for long time constant The waveform e(t) is illustrated in Figure 6C.6 e p (t) K ⋅ U p ⋅ V (t) t IEC Figure 6C.6 – Typical waveform of e(t) during test BS EN 61869-6:2016 – 78 – IEC 61869-6:2016  IEC 2016 Annex 6D (informative) Test circuits 6D.1 Test circuits for accuracy measurements in steady state for low-power current transformers Figure 6D.1, Figure 6D.2 and Figure 6D.3 show some basic circuits for the direct measurement of a composite error for the current transformer Reference CT P2 EUT Ip P1 P2 P1 Kr S2 S2 S1 R1 V1 Lock-in amplifier Rc S1 V lpcs R lpcs IEC Key Kr Rated transformation ratio of reference CT V1 Voltage at the input of the lock-in amplifier R1 Burden used to adjust the voltage at the input of the lock-in amplifier R1 + Rc Rated secondary burden of reference CT V lpcs Secondary voltage for low-power current transformer R lpcs Rated secondary burden of low-power current transformer R and R lpcs are required to be high accuracy burden The voltage at the input of the lock-in amplifier shall be adjusted in rated conditions This voltage shall be equal to the rated secondary voltage Figure 6D.1 – Test circuit for analogue accuracy measurements in steady state BS EN 61869-6:2016 IEC 61869-6:2016  IEC 2016 – 79 – Reference CT P2 EUT Ip P1 P2 P1 Kr S2 S1 S2 R lpcs S1 Is V lpcs Voltage/current converter Rc I’ s Current Comparator IEC Key Kr Rated transformation ratio of reference CT Is Secondary current for reference CT I′ s Secondary current for low-power current transformer V lpcs Secondary voltage for low-power current transformer with analogue output Rc Rated secondary burden of reference CT R lpcs Rated secondary burden of low-power current transformer Figure 6D.2 – Test circuit for analogue accuracy measurements in steady state (alternative solution) BS EN 61869-6:2016 – 80 – IEC 61869-6:2016  IEC 2016 Reference CT P2 EUT Ip P1 P2 P1 Kr S2 S1 S2 Rlpcs S1 Is Vlpcs Rc R1 Reference A/D converter V1 Reference A/D converter is (n) iref (n) Clock Evaluation (for example PC) ε, ϕe IEC Key Kr Rated transformation ratio of reference CT V1 Voltage at the input of the reference A/D converter V lpcs Secondary voltage for low-power current transformer with analogue output R1 Burden used to adjust the voltage at the input of the reference A/D converter R1 + Rc Rated secondary burden of reference CT R lpcs Rated secondary burden of low-power current transformer R1 is required to be a high accuracy burden Figure 6D.3 – Test circuit for digital accuracy measurements in steady state BS EN 61869-6:2016 IEC 61869-6:2016  IEC 2016 – 81 – 6D.2 Test circuits for accuracy measurements in steady state for low-power voltage transformers Figure 6D.4, Figure 6D.5 and Figure 6D.6 show some basic circuits for the direct measurement of an error for the voltage transformer S1 S1 P1 Vp Kr P1 EUT Reference VT P2 S2 S2 R1 V1 Lock-in amplifier P2 Vlpvs Rlpvs IEC Key Kr Rated transformation ratio of reference VT V1 Voltage at the input of the lock-in amplifier R1 Burden used to adjust the voltage at the input of the lock-in amplifier R1 + Rc Rated secondary burden of reference VT V lpvs Secondary voltage for low-power voltage transformer R lpvs Rated secondary burden of low-power voltage transformer R and R lpvs are required to be high accuracy burden The voltage at the input of the lock-in amplifier shall be adjusted in rated conditions This voltage shall be equal to the rated secondary voltage Figure 6D.4 – Test circuit for analogue accuracy measurements in steady state BS EN 61869-6:2016 – 82 – IEC 61869-6:2016  IEC 2016 S1 S1 P1 P1 Vp Kr EUT Reference VT P2 S2 S2 Rc P2 Rlpcs V1 Vlpcs Standard Voltage/current converter Standard Voltage/current converter Current Comparator IEC Key Kr Rated transformation ratio of reference VT Vs Secondary voltage for reference VT V′ s Secondary voltage for low-power voltage transformer V lpcs Secondary voltage for low-power voltage transformer with analogue output Rc Rated secondary burden of reference VT R lpcs Rated secondary burden of low-power voltage transformer Figure 6D.5 – Test circuit for analogue accuracy measurements in steady state (alternative solution) BS EN 61869-6:2016 IEC 61869-6:2016  IEC 2016 – 83 – S1 S1 P1 Vp Kr P1 EUT Reference VT P2 S2 S2 P2 Rlpvst Rc V1 Vlpvs Rc Reference A/D converter Reference A/D converter vis (n) vref (n) Clock Evaluation (for example PC) ε, ϕe IEC Key Kr Rated transformation ratio of reference VT V1 Voltage at the input of the reference A/D converter V lpvs Secondary voltage for low-power voltage transformer with analogue output R1 Burden used to adjust the voltage at the input of the reference A/D converter R1 + Rc Rated secondary burden of reference VT R lpvs Rated secondary burden of low-power voltage transformer R1 is required to be a high accuracy burden Figure 6D.6 – Test circuit for digital accuracy measurements in steady state BS EN 61869-6:2016 – 84 – IEC 61869-6:2016  IEC 2016 Annex 6E (informative) Graph explaining the accuracy requirements for multi-purpose low-power current transformer The graph in Figure 6E.1 shows the accuracy limits of a multipurpose low-power current transformer (i.e an LPIT which obeys measuring and protective requirements), which is also specified for transient response The marks show at which primary current the accuracy is actually tested during type tests The lines show in which primary current range the accuracy is supposed to be maintained Accuracy for measuring (amplitude error) Error % Accuracy for protection (composite error) Accuracy for transient response (peak) Ipr I epr = K pcr ⋅ I pr KALF ⋅ Ipr Ipsc = Ith Kssc ⋅ Ipr Ip IEC Figure 6E.1 – Accuracy limits of a multi-purpose low-power current transformer If an application requires a small deviation between the phase and/or amplitude error between the low-power current transformers on different phases, the user shall select a set of lowpower current transformers with similar calibration data, as is also done with conventional transformers The calibration data is available from routine testing A special test is not needed BS EN 61869-6:2016 IEC 61869-6:2016  IEC 2016 – 85 – Bibliography IEC 60044-7:1999, Instrument transformers – Part 7: Electronic voltage transformers IEC 60044-8:2002, Instrument transformers – Part 8: Electronic current transformers IEC 60050-321:1986, transformers International Electrotechnical Vocabulary – Chapter 321: Instrument IEC 60050-421:1990, International Electrotechnical Vocabulary – Chapter 421: Power transformers and reactors IEC 61508-1, Functional safety of electrical/electronic/programmable electronic safetyrelated systems – Part 1: General requirements IEC 61508-3, Functional safety of electrical/electronic/programmable electronic safetyrelated systems – Part 3: Software requirements IEC 61850 (all parts), Communication networks for power utility automation IEC 61869 (all parts), Instrument transformers IEC 61869-5, transformers Instrument transformers – Part 5: Additional requirements for capacitor voltage IEC 61869-7 transformers IEC 61869-8 transformers IEC 61869-9, Instrument transformers – Part 7: Additional requirements for electronic voltage Instrument transformers – Part 8: Additional requirements for electronic current Instrument transformers – Part 9: Digital interface for instrument transformers IEC 61869-10, Instrument transformers – Part 10: Specific requirements for low power passive current transformers IEC 61869-11, Instrument transformers – Part 11: 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