IEC TR 61869-103:2012

IEC/TR 61869-103 ®
Edition 1.0 2012-05
TECHNICAL
REPORT
colour
inside
Instrument transformers – The use of instrument transformers for power quality
measurement
IEC/TR 61869-103:2012(E)
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IEC/TR 61869-103 ®
Edition 1.0 2012-05
TECHNICAL
REPORT
colour
inside
Instrument transformers – The use of instrument transformers for power quality

measurement
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
XC
ICS 17.220.20 ISBN 978-2-88912-073-4

– 2 – TR 61869-103  IEC:2012(E)
CONTENTS
FOREWORD . 6
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 9
4 Nature of the problem . 12
5 Power quality parameters according to IEC 61000-4-30:2008 . 13
5.1 General . 13
5.2 Power quality measurement chain . 13
5.3 Signal processing according to IEC 61000-4-30:2008 . 14
5.4 Power frequency . 15
5.5 Magnitude of the supply voltage . 15
5.6 Flicker . 15
5.7 Supply voltage dips and swells . 17
5.8 Voltage interruptions . 18
5.9 Transient voltages . 19
5.10 Supply voltage unbalance . 19
5.11 Voltage harmonics . 20
5.12 Voltage inter-harmonics . 21
5.13 Mains Signalling Voltages on the supply voltage . 21
5.14 Rapid voltage changes . 21
5.15 Measurement of underdeviation and overdeviation parameters . 21
5.16 Summary of the requirements placed by the measure of power quality
parameters . 21
6 Impact of instrument transformers on PQ measurement . 22
6.1 General . 22
6.2 Inductive instrument transformers . 24
6.2.1 Inductive voltage transformers . 25
6.2.2 Inductive CTs . 30
6.3 Capacitive voltage transformers (CVTs) . 35
6.3.1 Standard application . 35
6.3.2 Special measurement techniques . 39
6.4 Electronic instrument transformers . 42
6.4.1 General . 42
6.4.2 Common accuracy classes . 42
6.4.3 Electronic VTs . 43
6.4.4 Electronic CTs . 55
7 Tests for power quality . 67
7.1 Test procedure for VT frequency response . 68
7.2 Test set-up for VT frequency response test . 68
7.3 Test procedure for CT frequency response . 70
7.4 Test set-up for CT frequency response test . 70
7.5 Special considerations for test of electronic instrument transformers with
digital output . 72
7.6 Tests for electronic instrument transformers according to IEC Standard
60044-8 . 72
7.6.1 Test arrangement and test circuit . 73

TR 61869-103  IEC:2012(E) – 3 –
Annex A Instrument transformers and power quality measurement – open issues . 75
Annex B Transformer classes . 79
Bibliography . 81

Figure 1 – Measurement chain (From [8], modified) . 14
Figure 2 – Contribution of instrument transformers in overall measurement uncertainty
(from [9], modified) . 14
Figure 3 – Example of voltage fluctuation causing flicker . 16
Figure 4 – Demodulation within the IEC flickermeter . 17
Figure 5 – Example of voltage dip (courtesy of Italian distribution network monitoring
system – QuEEN) . 18
Figure 6 – Example of voltage interruption (courtesy of Italian distribution network
monitoring system – QuEEN) . 19
Figure 7 – Example of voltage unbalance (courtesy of Italian distribution network
monitoring system- QuEEN) . 20
Figure 8 – Example of voltage harmonics . 21
Figure 9 – Voltage transformer technologies frequency range according to present
experience . 23
Figure 10 – Current transformer technologies frequency range according to present
experience . 24
Figure 11 – Example of equivalent circuit for an inductive voltage/current transformer . 25
Figure 12 – Cross-section view of an inductive voltage transformer for voltages over 1
kV and up to 52 kV (courtesy of Schneider Electric) . 26
Figure 13 – Cross-section view of a freestanding High Voltage VT (courtesy of Trench
Switzerland AG) . 28
Figure 14 – Frequency response of a typical inductive VT 420 kV (courtesy of Trench
Switzerland AG) . 29
Figure 15 – First resonance peak depending on the system voltage U (courtesy of
m
Trench Switzerland AG) . 29
Figure 16 – Cross-section view of a current transformer (courtesy of Schneider
Electric) . 32
Figure 17 – Results obtained for a 245 kV CT (courtesy of Trench Switzerland AG) . 34
Figure 18 – Results obtained for a 245 kV CT: detail (courtesy of Trench Switzerland AG) . 34
Figure 19 – Cross-section view of a capacitive voltage transformer (Courtesy of Trench
Switzerland AG) . 35
Figure 20 – CVT: Equivalent circuit at power frequency . 36
Figure 21 – Simplified CVT Thevenin equivalent circuit at power frequency without
compensating reactor . 37
Figure 22 – Simplified CVT Thevenin equivalent circuit at power frequency . 37
Figure 23 – Complete CVT Thevenin equivalent circuit at power frequency . 38
Figure 24 – Measurements performed by means of a CVT with harmonic measurement
terminal . 40
Figure 25 – Comparison of different measurements with and without harmonic
monitoring terminal (Courtesy of Trench Switzerland AG, based on [16]) . 41
Figure 26 – Basic design for a bulk crystal producing a Pockels Effect (courtesy of
Alstom Grid) . 45
Figure 27 – Various solutions to apply voltage on the active crystal . 46
Figure 28 – Various methods to divide the full voltage before applying on the crystal . 46

– 4 – TR 61869-103  IEC:2012(E)
Figure 29 – Basic design for a Pockels sensor (courtesy of Alstom Grid) . 47
Figure 30 – Industrial bulk Pockels Cell (courtesy of Alstom Grid) . 47
Figure 31 – Frequency response calculation for an optical VT (courtesy of Alstom Grid) . 48
Figure 32 – Cross-section view and electrical scheme of a resistive voltage divider
(from [22]) . 49
Figure 33 – Ratio error of an MV resistive divider (courtesy of Trench Switzerland AG) . 50
Figure 34 – Phase error of MV resistive divider (courtesy of Trench Switzerland AG) . 50
Figure 35 – Electrical scheme of a capacitive voltage divider . 51
Figure 36 – Equivalent circuit of an RC voltage divider (from [23], [24]) . 53
Figure 37 – Equivalent circuit of a balanced RC voltage divider (from [24]) . 53
Figure 38 – Frequency response of an RC voltage divider (courtesy of Trench
...