IEC TS 62758:2012

IEC/TS 62758 ®
Edition 1.0 2012-09
TECHNICAL
SPECIFICATION
colour
inside
Calibration of space charge measuring equipment based on the pulsed electro-
acoustic (PEA) measurement principle

IEC/TS 62758:2012(E)
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IEC/TS 62758 ®
Edition 1.0 2012-09
TECHNICAL
SPECIFICATION
colour
inside
Calibration of space charge measuring equipment based on the pulsed electro-

acoustic (PEA) measurement principle

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
V
ICS 17.220.99; 29.035.01; 29.080.30 ISBN 978-2-83220-336-1

– 2 – TS 62758 © IEC:2012(E)
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Basic theory for measurement . 8
4.1 Permittivity and induced charge density . 8
4.2 Charge in dielectrics and Poisson’s law . 8
4.3 Coulombic force of charge in electric field . 9
4.4 Reflection and transmission of pressure wave . 9
4.5 Maxwell stress . 9
4.6 Response of linear system . 10
5 Procedure to calibrate the space charge measurement . 10
5.1 Principle of calibration . 10
5.1.1 General . 10
5.1.2 Typical result of calibration measurement . 11
5.2 Sample preparation . 12
5.2.1 Sample for calibration measurement . 12
5.2.2 Sample placement . 13
5.3 Data acquisition . 13
5.3.1 Pulse voltage test . 13
5.3.2 Averaging . 13
5.3.3 Data acquisition for calibration . 14
5.3.4 Signal obtained under short circuit condition . 15
5.4 Data processing and calibration . 15
5.4.1 Deconvolution . 15
5.4.2 Calibration for horizontal axis and calculation of waveform for electric
field distribution . 16
5.4.3 Calibration for electric field and charge density distributions . 16
5.4.4 Confirmation of linearity of measurement . 17
5.4.5 Typical test results by expert members of project team . 17
Annex A (informative) Theory of PEA method . 21
Bibliography . 35

Figure 1 – Theoretical distributions for calibration measurement . 11
Figure 2 – Typical result of calibration measurement . 12
Figure 3 – Drop of silicone oil and sample placement . 13
Figure 4 – Pulse voltage application test . 13
Figure 5 – Dependence of averaging number . 14
Figure 6 – Measurement of waveform for calibration . 15
Figure 7 – Confirmation of absence of space charge accumulation during d.c. voltage
application for calibration . 15
Figure 8 – Deconvolution and calibration . 16
Figure 9 – Calibration for electric field and charge density distributions . 17

TS 62758 © IEC:2012(E) – 3 –
Figure 10 – Confirmation of linearity measurement . 17
Figure 11 – Results of calibration test by research Group A . 18
Figure 12 – Results of calibration test by research Group B . 18
Figure 13 – Results of calibration test by research Group C . 19
Figure 14 – Results of calibration test by research Group D . 19
Figure 15 – Results of calibration test by research Group E . 19
Figure A.1 – Principle of acoustic wave generation in PEA method . 22
Figure A.2 – Pressure wave propagation in PEA measurement system . 24
Figure A.3 – Response of piezo-transducer . 25
Figure A.4 – Transform from pressure to amount of charge induced on piezo-
transducer . 25
Figure A.5 – Relationship between the pulse width and thickness of piezo-transducer . 26
Figure A.6 – Adequate spatial resolution . 27
Figure A.7 – Example of two types of signal . 29
Figure A.8 – Calculation flow for deconvolution . 30
Figure A.9 – Effect of Gaussian filter . 31
Figure A.10 – PEA measurement apparatus . 32
Figure A.11 – Equivalent circuit for voltage application . 33
Figure A.12 – Equivalent circuit for signal detection . 34

Table 1 – Measurement resolution . 20

– 4 – TS 62758 © IEC:2012(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
CALIBRATION OF SPACE CHARGE MEASURING EQUIPMENT BASED ON
THE PULSED ELECTRO-ACOUSTIC (PEA) MEASUREMENT PRINCIPLE

FOREWORD
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IEC 62758, which is a technical specification, has been prepared by technical committee 112:
Evaluation and qualification of electrical insulating materials and systems.

TS 62758 © IEC:2012(E) – 5 –
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