IEC · IEC · IEC · IEC · IEC · IEC ; Show all». IEC Standard | Guide for the determination of thermal endurance properties of ekectrical insulating materials – Part 2: List of. IEC , Electrical insulating materials – Thermal endurance properties – Part 2: Determination of thermal endurance properties of electrical.
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NOTE 2 Attention should be given to the recommendation in 5. Throughout the rest of this standard the term “insulating materials” is always taken to mean “insulating materials and simple combinations of such materials”. When the criterion is an absolute property level, n d is usually given the value of zero, unless reporting of the initial value is required. Instructions for an adequate number of specimens are given in IEC Simultaneously with the development of the IEC series, other standards were being developed in ISO, intended to satisfy a similar requirement for plastics and rubber materials.
Find out more about British Standards by visiting our website at bsigroup. An approximately linear region of the ageing graph is selected Figure 3 and a line parallel to the mean ageing graph drawn through each time, property point.
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In the case of proof tests with incomplete data usually censored at the medianit may be possible to obtain a sufficient increase in data group size by continuing the exposure until further test specimens have failed the proof test.
For the valid application of the standard, no transition, in particular no first-order transition should occur in the temperature range under study. Instructions for calculating thermal endurance characteristics using simplified procedures. In such cases it is often convenient to start by iecc the ageing oven with one-half of the prepared specimens and performing measurements after the second or third exposure cycle eic the recommended series.
At the same time, the calculation procedures were made more comprehensive, enabling full statistical testing of data obtained using a diagnostic property of any type, including the particular iex of partially incomplete data. The circulation of the air within the oven and the exchange of the air content should be adequate to ensure that the rate of thermal degradation is not influenced by accumulation of decomposition products or oxygen depletion see 5.
Methods based on mean values lec normally distributed test results 3 3.
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BSI is incorporated by Royal Charter. In this way, any required ageing of additional specimens in case of unforeseen complications will introduce a minimum risk of producing systematic differences between groups of specimens. It is not necessary for all groups to be equal in size or for equal numbers to have failed.
If not, the assumption is a priori rejected, but, since in special cases it is possible to detect a statistically significant non-linearity which is of little practical importance, the calculations may, under specified conditions, be continued in a modified way for details, see IEC Where the test criterion for non-destructive or proof tests is based upon the initial value of the property, this should be determined from a group iiec specimens of at least twice the number of specimens in each temperature group.
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This value might be selected with respect to usual service requirements. The degree of degradation indicated as the end-point of iev test should be related to the allowable safe value for the material property which is desired in practice. In order to carry out valid calculations, one or more further group s of specimens shall be aged at such a lower temperature as will enable the conditions to be met.
Determination of thermal endurance properties of electrical insulating materials Choice of test criteria Electrical insulating materials – Thermal endurance properties Part 3: This led to the concept of the “Thermal Endurance Profile” TEPincorporating the temperature index, its variation with specified ageing time, and a confidence limit.
Although isc developed for use with electrical insulating materials and simple 6021-2 of such materials, the procedures are considered to be of more general applicability and are widely used in the assessment of materials not intended for use as electrical insulation. To reduce the uncertainties in calculating the appropriate thermal endurance characteristic, the overall jec range of thermal exposure needs to be carefully selected, observing the following requirements if the required thermal endurance characteristics are for a projected duration of 20 Relevant and detailed instructions on how to proceed using non-destructive, proof or destructive test criteria are provided in 5.
Where there is no risk of ambiguity, either temperature groups or test groups may be referred to simply as groups. Buying standards You can buy and download PDF versions of BSI publications, including British and adopted European and international standards, through our website at bsigroup. It is permitted for these conditions not to be satisfied in specified circumstances either a small extrapolation or linearity test at significance level 0, may be permitted; see 6.
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These tests have been designed to test all important aspects of the data which might invalidate derivation of thermal endurance characteristics, as well as to decide whether a failure to satisfy the statistical requirements is of practical significance.
Except as permitted under the Copyright, Designs and Patents Act no extract may be reproduced, stored in a retrieval system or transmitted isc any form or by any means — electronic, photocopying, recording or otherwise — without prior written permission from BSI. If, for example, Group C idc reached end-point nine cyclesGroups G, H and I would have received respectively six, seven and eight cycles at testing.
Unless otherwise stated in the method for determining the diagnostic property for example, parts of material specifications dealing with methods of test, or a method listed in IECthe initial value is the arithmetic 6216-2 of the test results.
However, the statistical tests were considered essential, particularly after minor modifications to make them relate better to practical circumstances: The parameters are referred to as the regression coefficients. Licences can cover as few or as many users as you wish. It is necessary to ensure that the intercept of the regression line with the time axis gives the same value as the mean of the intercepts of the individual lines.
The intercept of this line with the end-point line gives the logarithm of the required time to end-point see Figure 4. We jec improve the quality of our products and services to benefit your business. The cycles of temperature exposure may be 602162- until all specimens have failed, so that a more complete statistical analysis may be made see IEC In addition to the above-mentioned basic assumption, some ief assumptions regarding the chemical mechanisms of 60216-22 thermal ageing need to be satisfied: This standard is concerned only with type 2.
A complicating factor is that the properties of a material subjected to thermal ageing may not all deteriorate at the same rate, and different end-points may be relevant for different applications.
At the end of each cycle, remove all specimens from the oven. If such material specifications are not available, a selection of properties and methods for the evaluation of thermal endurance is given in IEC In this way, the total amount of testing is reduced, without loss of discrimination. Consequently, a material 6216-2 be assigned more than one thermal endurance characteristic derived from the measurement of properties at different thicknesses.
Since processing conditions may significantly affect the ageing characteristics 6216-2 some materials, it shall be ensured that, for example, sampling, cutting sheet from the supply roll, cutting of anisotropic material in a given direction, molding, curing, pre-conditioning, are performed in the same manner for all specimens. Values of the abscissa are proportional to the reciprocal of the thermodynamic absolute temperature.
The correct usage is restricted to such a relationship between a reaction rate constant and the thermodynamic temperature. Copyright All the data, software and documentation set out in all British Standards and other BSI publications are the property of and copyrighted by BSI, or some person or entity that owns copyright in the information used such as the international standardization bodies and has formally licensed such information to BSI for commercial publication and use.