IEC. Fourth edition. Electrical insulating materials – +41 22 02 11 Telefax: +41 22 03 00 E-mail: [email protected] Web: 标准 IEC 电气绝缘材料 耐热性 第1部分：老化程序和试验结果的 评定_电力/水利_工程科技_专业资料。标准 IEC 电气. this publication, including its validity, is available in the IEC Catalogue of IEC Electrical insulating materials – Properties of thermal endurance.
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Table 1 gives guidance in making initial selections. It is not necessary for all groups to be equal in size or for equal numbers to have failed. The cycles of temperature exposure may be continued until all specimens have failed, so that a more complete statistical analysis jec be made see IEC In cases of shorter specification times, the related times may be decreased in the same ratio if necessary.
In such cases, it may be possible to obtain an acceptable result by further testing at a lower temperature.
The correct usage is restricted to such a relationship between a reaction rate constant and the thermodynamic temperature. Organizations of all sizes and across all sectors choose standards to help them achieve their goals. For graphical derivation and in some other cases the treatment of data may be simpler if the number of specimens in each group is odd.
If end-point is reached in one of the Groups B — F, Groups G — I are immediately removed from the oven and tested after conditioning. It was felt to be much more important that assurance could be given that the difference between the calculated TI and its lower confidence limit was less than a specified value. 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.
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Ageing at lower temperature s of one or two additional group s of specimens in case of suspected non-linearity can then be initiated immediately to produce the complete test data within a time limit which is still acceptable. However, environmental conditioning, the influence of atmospheres other than air and immersion in liquids such as oil may be important, but these are not the concern of this standard.
A choice ief properties is given in IEC For non-destructive tests, although Table 1 suggests constant cycle lengths, test times following a geometric series may be used.
The following test report forms are related: Instructions for calculating thermal endurance characteristics IEC all Parts 46026-1 insulating materials — Thermal endurance properties — Iev 4: Note 2 to entry: Very long specification times may also lead to non-linearity see also Annex A. The characteristic has now been made the subject of a new, independent standard in preparation.
Times to end-point, x – and y -values General 6. 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 mean of the test results.
Such complications may arise, for example, if the thermal endurance relationship turns out to be non-linear, or if specimens are lost due to thermal runaway of an oven.
Evaluate the results, as listed in 6. In the application of 60216- standard, it is assumed that a practically linear relationship exists between the logarithm of the time required to cause the predetermined property change and the reciprocal of the corresponding absolute temperature Arrhenius relationship.
However, the statistical tests were considered essential, particularly after minor modifications to make them relate 6016-1 to practical circumstances: If the data dispersion is not high through inadequate experimental technique, the effect of the high dispersion can be overcome by the use of a larger number of data values, i.
Place one group for exposure in each of the ovens complying with 5.
This value might be selected with respect to usual service requirements. However, further guidance will be found in IEC Instructions for calculating thermal endurance characteristics using simplified procedures.
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Instructions for an adequate number of specimens are given in IEC The format of the TI is then: The thermal endurance of an electrical insulating material is always given for a specific property and end-point. Physico-chemical models postulated for the ageing processes led to the almost universal assumption of the Arrhenius equations to describe the rate of ageing. We accept all major credit cards American Express, Mastercard and VisaPayPal and bank transfers as form of payment.
However, it ied important that a smaller range of mean times to end-point will lead to a larger confidence interval of the result for the same data dispersion. This led to the concept of the “Thermal Endurance Profile” TEPincorporating the temperature index, its variation with specified ageing time, and a confidence limit.
In obtaining the RTI, the systematic errors observed in the determination of TI are to a large extent compensated. isc
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In this test, a test parameter F is calculated from the experimental data and compared with a tabulated value F 0. Ageing procedures and evaluation of test results 1 Scope This part of IEC specifies the general ageing conditions and procedures to be used for deriving thermal endurance characteristics and gives guidance in using the detailed instructions and guidelines in the other parts of the standard.
The thickness of specimens is in some cases specified in the list of property measurements for the determination of thermal endurance. To achieve this, select the cycle length so that the mean or median time to end-point is reached in about 10 cycles but not less than seven. Ageing procedures and evaluation of test results IEC TC – Evaluation and qualification of electrical insulating materials and systems rss. This will have the effect of decreasing the extrapolation, which is one of the influences in determining the size of the confidence interval, and also make the errors associated with the non-linearity less serious.