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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However, for some materials very sensitive to the humidity in the ovens, more reliable results are obtained when the absolute humidity in the ageing oven room is controlled and equal to the absolute humidity corresponding to standard atmosphere B according to IEC Although originally developed for use with electrical insulating materials and simple combinations 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.
The reference level may for 6026-2, be a mean value one parameter or lec line two parameters, slope and intercept. This edition constitutes an editorial revision where the simplified method has been removed and now forms Part 8 of the EN Series: Methods based on mean values of normally distributed test results 3 3.
The cycles of temperature exposure may be continued until all specimens have failed, so that a more complete statistical analysis may be made see IEC Determination of thermal endurance properties of electrical insulating materials Choice of test criteria Electrical insulating materials – Thermal endurance properties Part 3: If this rule idc in changes of mechanism for example, when a transformation point like melting or softening is exceeded iecc, then the maximum exposure temperature will need to be limited.
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Groups are tested as indicated in the table. The IEC series has been developed to formalize these procedures and the interpretation of their results. Generally, the following instructions 5. It is strongly recommended that the full evaluation 60261-2, as 602166-2 below and in 5.
NOTE The ageing graph is formed by plotting the value of property or a suitable transform of its value against 602116-2 logarithm of the exposure time. 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.
The application of conventional statistical tests, as set out in IECfulfilled this requirement, resulting in the “confidence limit”, TC of TI, but the simple, single-point TI was found inadequate to describe the capabilities of materials. For undated references, the latest edition of the referenced document 60216- any amendments applies. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights.
If necessary, determine the initial value of the property as specified in 5.
The size of the confidence interval is ie proportional to the square root of the reciprocal of the total number of data values. Some physical properties are sensitive even to minor variations of specimen thickness. If the data dispersion is not high iwc inadequate experimental 602116-2, the effect of the high dispersion can be overcome by the use of a larger number of data values, i. At the same time, the 6021-2 procedures were made more comprehensive, enabling full statistical testing of data obtained using a diagnostic property of any type, including the particular case of partially incomplete data.
The end-point should be selected to indicate a degree of deterioration of the insulating material which has reduced its ability to withstand a stress encountered in actual service in an insulation system.
The regression analysis for slope and intercept of the thermal endurance graph and the tests for deviations 06216-2 linearity shall be as 06216-2 6.
The first assumption is tested by the so-called Fisher test 602162- -test. 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. 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 62016-2, the calculations may, under specified conditions, be continued in a modified way for details, see IEC This approach will provide comparisons among materials but bears a poorer relationship than item b to the property values required in normal service.
Instead, the trend of the thermal endurance relationship may be roughly estimated after the first or second failure at the lowest ageing temperature of the original programme. NOTE 2 When extending the test program by submitting additional specimens to ageing at temperatures below the lower of the originally planned ageing temperatures, a temperature interval of 10 K and a cycle duration of 42 days for TI determination should be considered.
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. In such cases, it may be possible to obtain an acceptable result by further testing at a lower temperature.
Since processing conditions may significantly affect the ageing characteristics of some 60216- 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.
In the 60216-22 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. The degree of degradation indicated as the end-point of the test should be related to the allowable safe value for the material property which is desired in practice.
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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.
Some test properties may require measurement kec the oven temperature, in which case the ageing is continuous. However, environmental conditioning, the influence of iwc other than air and immersion in liquids such as oil may be important, but these are not the concern of this standard.
For destructive tests, see 5. The following dates are fixed: The parameters are referred to as the regression coefficients.
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The intercept of this line with the end-point line gives the logarithm of the required time to end-point see Figure 4. 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.
At the end of each cycle, remove all specimens from the oven. Out of this arose the concept of the temperature index TI as a single-point characteristic based upon accelerated ageing data.