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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Five of the test groups are placed in the oven at the beginning of the sequence. Continue the cycles of temperature exposure, cooling and application of the test until the average measured value for the specimens in the group has reached the end-point specified and provided at least one point beyond the end-point.
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 60216- practical significance.
Avenue Marnix 17, B – Brussels? For the determination of the initial value, see 5.
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Using Equations 46 to 50 of 6. In the same way, calculate the temperature? 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.
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 In some cases for example, very thick specimenstimes greater than two days may be necessary to establish a stable value.
Figure 4 — Destructive tests — Estimation of time to end-point 6. Return specimens which have withstood the proof test to the oven from which they came, at the same temperature as before, and expose for a further cycle. After each removal, allow the specimens to cool to room temperature and then subject each one to the specified proof test.
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.
Instructions for calculating thermal endurance characteristics using simplified procedures. Together with BS EN If you need international and foreign standards from other Standards Development Organizations, hard copies can be ordered from our Customer Services team.
Throughout the rest of this standard the term “insulating materials” is always taken to mean “insulating materials and simple combinations of such materials”. 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.
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.
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.
NOTE 1 It is suggested that individual specimens be identified to simplify their return to the correct oven after each test. In the application of this 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.
In this test, a test parameter F is calculated from the experimental data and compared with a tabulated value F 0. At the end of each cycle, remove all specimens from the oven.
In the official version, for Bibliography, the following notes have to be added for the standards indicated: Further guidance will be found in IEC 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 advisable to distinguish between: This model is valid when the selected end-point of the diagnostic property is correlated with a particular degree of molecular change in the material which is subject to ageing. The regression analysis for slope and intercept of the thermal endurance graph and the tests for deviations from linearity shall be as in 6.
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This approach will provide comparisons among materials but bears a poorer relationship than item b to the property values required in normal service. Generally, the following instructions 5.
Relevant and detailed instructions on how to proceed using non-destructive, proof or destructive test criteria are provided in 5. NOTE The ageing graph is formed by plotting the value of property or a suitable transform of its value against the logarithm of the exposure time.
Consequently, a material may be assigned more than one thermal endurance characteristic derived from the measurement of properties at different thicknesses. These may be briefly expressed as follows see 3.
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.
Divide the specimens by random selection into as many groups as there are exposure temperatures. Ageing data of materials with different thicknesses are not always comparable. The intercept of this line with the end-point line gives the logarithm of the required time to end-point see Figure 4.
Times to end-point, x – and y -values General 6.
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However, further guidance will be found in IEC We continually improve the quality of our products and services to benefit your business. 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 Consequently, a material may be assigned more than one temperature index or halving interval derived, for example, from the measurement of different properties.
It was subsequently found that the statistical confidence index included in the TEP was not widely understood or used. Early results of the ageing test may motivate an adjustment of ageing cycles or additional ageing temperatures.