1、 IEC/TR 62836 Edition 1.0 2013-09 TECHNICAL REPORT Measurement of internal electric field in insulating materials Pressure wave propagation method IEC/TR 62836:2013(E) colour inside THIS PUBLICATION IS COPYRIGHT PROTECTED Copyright 2013 IEC, Geneva, Switzerland All rights reserved. Unless otherwise
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9、n insulating materials Pressure wave propagation method INTERNATIONAL ELECTROTECHNICAL COMMISSION M ICS 17.220.99; 29.035.01 PRICE CODE ISBN 978-2-8322-1102-1 Registered trademark of the International Electrotechnical Commission Warning! Make sure that you obtained this publication from an authorize
10、d distributor. colour inside 2 TR 62836 IEC:2013(E) CONTENTS FOREWORD . 3 INTRODUCTION . 5 1 Scope 6 2 Terms, definitions and abbreviations . 6 2.1 Terms and definitions . 6 2.2 Abbreviations . 6 3 Principle of the method 6 4 Sample conditions . 8 5 Electrode materials 8 6 Pressure pulse wave genera
11、tion 8 7 Set-up of the measurement 8 8 Calibrating the electric field . 9 9 Measurement procedure 9 10 Data processing for the experimental measurement . 9 11 Measurement examples . 10 11.1 Samples . 10 11.2 Pressure pulse generation . 10 11.3 Calibrating of sample and signal 10 11.4 Testing sample
12、and experimental results . 11 11.5 The internal electric field distribution 12 Figure 1 Principle of the PWP method 7 Figure 2 Set-up of measurement of the PWP method . 8 Figure 3 Sample of protecting circuit 9 Figure 4 Current signal under 5,8 kV 11 Figure 5 First measured current signal ( 1 min) 1
13、1 Figure 6 Signal under 46,4 kV, 1,5 h 11 Figure 7 Measured signal without applied voltage, after 1,5 h under high voltage 12 Figure 8 Internal electric field distribution under 5,8 kV 12 Figure 9 Internal electric field distribution under 46,4 kV, at the initial state . 12 Figure 10 Internal electr
14、ic field distribution under 46,4 kV, after 1,5 h under high voltage 12 Figure 11 Internal electric field distribution without applied voltage after 1,5 h under high voltage 12 TR 62836 IEC:2013(E) 3 INTERNATIONAL ELECTROTECHNICAL COMMISSION _ MEASUREMENT OF INTERNAL ELECTRIC FIELD IN INSULATING MATE
15、RIALS PRESSURE WAVE PROPAGATION METHOD FOREWORD 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international co-operation on all ques
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25、n. 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent rights. IEC shall not be held responsible for identifying any or all such patent rights. The main task of IEC technical committees is to prepare International Standards. However
26、, a technical committee may propose the publication of a technical report when it has collected data of a different kind from that which is normally published as an International Standard, for example “state of the art“. IEC/TR 63836, which is a technical report, has been prepared by IEC technical c
27、ommittee 112: Evaluation and qualification of electrical insulating materials and systems. The text of this technical report is based on the following documents: Enquiry draft Report on voting 112/258/DTR 112/263/RVC Full information on the voting for the approval of this technical report can be fou
28、nd in the report on voting indicated in the above table. This publication has been drafted in accordance with the ISO/IEC Directives, Part 2. 4 TR 62836 IEC:2013(E) The committee has decided that the contents of this publication will remain unchanged until the stability date indicated on the IEC web
29、 site under “http:/webstore.iec.ch“ in the data related to the specific publication. At this date, the publication will be reconfirmed, withdrawn, replaced by a revised edition, or amended. A bilingual version of this publication may be issued at a later date. TR 62836 IEC:2013(E) 5 INTRODUCTION Hig
30、h-voltage insulating cables, especially high-voltage d.c. cables, are subject to charge accumulation and thus to electrical breakdown if the electric field produced by the charges exceeds the electrical breakdown threshold. With the trend to multiply power plants, especially green power plants such
31、as wind or solar generators, more cables will be used for connecting these power plants to the grid and share the electric energy between countries. Therefore the materials for the cables, and even the structure of these cables when considering electrodes or the junction between cables, need a stand
32、ardized procedure for testing how the internal electric field can be characterized. The measurement of the internal electric field would give a tool for comparing materials and help to establish thresholds on the internal electric field for high voltage applications in order to limit as much as poss
33、ible breakdown risks. The pressure wave propagation (PWP) method has been used by several researchers to measure the space charge distribution and the internal electric field distribution in insulators. However, since experimental equipment, with slight differences, is developed independently by res
34、earchers over the world, it is difficult to compare the measuring results between the different researchers. The procedure outlined in this technical report would give a reliable point of comparison between different test results carried out by different laboratories and avoid interpretation errors.
35、 The IEC has established a project team to develop a procedure to evaluate PWP measurement. The method will be verified in a Round Robin test. Once, having received reliable experience, this report is intended later to be upgraded to a technical specification in order to establish a specified way to
36、 estimate fairly the performance of a PWP measurement. 6 TR 62836 IEC:2013(E) MEASUREMENT OF INTERNAL ELECTRIC FIELD IN INSULATING MATERIALS PRESSURE WAVE PROPAGATION METHOD 1 Scope IEC/TR 62836, which is a technical report, contains an efficient and reliable procedure to test the internal electric
37、field in the insulating materials used for high-voltage applications using the pressure wave propagation (PWP) method. It is suitable for a sample with homogeneous insulating materials and an electric field higher than 1 kV/mm, but it is also depended on the thickness of sample and the pressure wave
38、 generator. 2 Terms, definitions and abbreviations For the purposes of this document, the following terms, definitions and abbreviations apply. 2.1 Terms and definitions 2.1.1 pressure wave propagation PWP propagation of wave generated by the action of a pressure pulse 2.2 Abbreviations LIPP laser i
39、nduced pressure pulse PIPP piezoelectric induced pressure pulse 3 Principle of the method The principle of the PWP method is shown schematically in Figure 1. The space charge in the dielectric and the interface charge are forced to move by the action of a pressure pulse wave. The charge displacement
40、 then induces an electrical signal in the measuring circuit which is an image of the charge distribution in the short-circuit current measurement condition. The expression for the short-circuit signal is dx t t x p x E C t i d = 0 0 ) , ( ) ( B ) ( (1) where E(x) is the electric field distribution i
41、n the sample; d is the thickness of sample; p(x, t) is the pressure pulse wave in the sample, which depends on the electrode materials, dielectric sample material, the condition of coupling on the interface, etc.; C 0 is the sample capacitance without the action of pressure pulse wave. C 0depends on
42、 the thickness of sample, and its surface area which is equal to the area of action of pressure pulse wave. The constant B = x (1 a ) only depends on the characteristics of the dielectric materials. For heterogeneous dielectric materials, B is a function of space. For homogeneous dielectric material
43、s, B is not a function of space and can be put in front of the integral. In this proposition, only homogeneous dielectric materials are considered, B is a constant. In Equation (1), the electric field distribution can be obtained if it is deconvolved. TR 62836 IEC:2013(E) 7 (x) x E(x) i(t) p(x,t) V
44、sX fi(t) x d d 00 t 0 IEC 2370/13 Figure 1a Applied pressure pulse and measured short-circuit current signal R C i(t) 50 Sample HV Pressure pulse wave Protecting circuit Signal output IEC 2371/13 Figure 1b Measuring schematics Figure 1 Principle of the PWP method The applied pressure pulses can be g
45、enerated by different techniques, but the same kind of analysis can be done for any of these techniques. The main practical PWP method can be divided into two ways: a pressure pulse is induced by a powerful pulse laser, a technique called LIPP method, and a pressure pulse generated by a piezoelectri
46、c device, a technique called PIPP. The sensibility and resolution of PWP method depends mainly on the amplitude and width of pressure pulse. The advantage of the LIPP method is to produce high sensitive measurements. The advantage of the PIPP is to obtain a better spatial resolution. In the case of
47、a narrow pulse, e.g., the width of the pressure pulse is much less than the thickness of sample i( ) 0 d = 0 B ( = s ) ( , ) 0 dx (2) where ( 0 , x ) s is the pressure pulse duration; sis the sound speed in the sample; ( = s ) is the mean electric field during the pressure pulse width. 8 TR 62836 IE
48、C:2013(E) Because sound loss and sound dispersion in polymer dielectrics exist, the amplitude of p(x, t) will decrease, and the width of p(x,t) will increase during the propagation of a pressure pulse wave in the sample. But for the polymer dielectrics, the main action is the sound dispersion, therefore, even if p(x,t) is not a constant in the dielectrics, its integral ( , ) 0 dx remains constant during its propagation in the sample. From the above equation and from the signal obtained with a sample free of charges and submitted to an intermediate voltage V 0 , ( , ) 0 can be obtai
