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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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 After a few cycles, the remaining specimens can be placed in the oven and the points on the ageing curve property variation curve see Figures 2, 3 and 4which are deemed necessary, determined.

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. Where there is no risk of ambiguity, either temperature groups or test groups may be referred to simply as groups.

The thermal endurance characteristics are as derived in the calculations of 6. For destructive tests, see 5. If a time different from 20 h has been used for deriving the TI, the relevant time expressed in kh shall be stated, followed by kh. Prepare a number of specimens following the instructions in 5. Using Equations 46 to 50 of 6. The following test report forms are related: In the same way, calculate the temperature?

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TC – Evaluation and qualification of electrical insulating materials and systems 6026-1. Apply the appropriate test to each specimen and then return the group to the oven from which they came, at the same temperature as before, and expose for a further cycle. 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.

This model is 660216-1 when the selected end-point of the diagnostic property is correlated with a particular degree of idc change in the material which is subject to ageing.

It was subsequently found that the statistical confidence index included in the TEP was not widely understood or used.

### 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_百度文库

These further tests may be at lower or intermediate temperatures but should not generally be at higher temperatures than originally selected. Either a new group, possibly with a shorter cycle time, should be started, or the first cycle failure ignored ieec the nominal size of the group reduced by one for example, a temperature group of 21 would be treated in the mathematical process as 20; see 6.

Where the derivation is by the simplified procedure see IEC the format is: For some materials, it is not possible to achieve a time to end-point of less than h while retaining satisfactory linearity.

The analysis of TI data is based on the assumption that there is a linear relation between the logarithm of the time to end-point and the reciprocal of the thermodynamic ageing temperature. A list of organizations represented on this committee can be obtained on request to its secretary. If the results show that this time to end-point is likely to be reached in about 10 periods of exposure, there is no need to alter the period of exposure originally selected.

For the valid application of the standard, no transition, in particular no first-order transition should occur in the temperature range under study. General procedures for the determination of thermal endurance properties, temperature indices and thermal endurance profiles withdrawn ISOPlastics — Standard atmospheres for conditioning and testing ISO If either of these conditions is not met, the value of TI cannot be reported. If such information is not available, preliminary screening tests may be performed to produce a forecast of the value of TI.

In the case of destructive tests 6. Ascending order in this standard implies that the data is ordered in this way, the first orderstatistic being the smallest.

If such a method cannot be found, an international, national, or institution standard, or a specially devised method should be used, and in that order of preference. 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 cases of shorter specification times, the related times may be decreased in the same ratio if necessary. 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 of specimens of at least twice the number of specimens in each temperature group.

Further guidance will be found in IEC In cases of longer times, for example, the times given as requirements or recommendations in the text of this standard for example, 5 h for the minimum value of the longest time to end-point shall be increased in the ratio of the actual specification time to 20 h.

A simplified procedure is available in IEC The thickness of specimens is in some cases specified in the list of property measurements for the determination of thermal endurance.

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Iecc sequential procedure may also be justified where the envisaged accuracy of the evaluation requires additional specimens to be aged, for example, in the case where the thermal endurance relationship turns out to be non-linear. In the same way, the ageing cycle durations should be changed in approximately the same ratio.

If the results do not show this, the period may be changed so that the median result may be expected in at least seven cycles preferably about 10 provided this change in cycle time is made before the fourth cycle.

For non-destructive tests, although Table 1 suggests constant cycle lengths, test times following a geometric series may be used. 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. The common usage is employed throughout this iiec. Some physical properties are sensitive even to minor isc of specimen thickness.

For materials in which a significant variation of properties with temperature or humidity is expected, unless otherwise specified, condition the specimens overnight in standard atmosphere B of IEC Ageing procedures and evaluation of test results IEC This sixth edition cancels and replaces the fifth edition, published in The thickness is also important because the rate of ageing may vary with thickness.

Accelerated ageing and test procedures were therefore required to obtain the necessary information. The method of evaluation of TI results is by the numerical procedure detailed in IEC together with a graphical presentation as shown in Figure 1. In the application of this standard, it is lec 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.

A simplified procedure is given in IEC