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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The intercept of this line with the end-point line gives irc logarithm 660216-2 the required time to end-point see Figure 4. 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.
Oec some materials, it is not possible to achieve a time to end-point of less than h while retaining satisfactory linearity. 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. In the case of destructive tests 6. A simplified calculation procedure is described in IEC If such information is not available, preliminary screening tests may be performed to produce a forecast of the value jec TI.
Organizations of all sizes and across all sectors choose standards to help them achieve their goals. In such cases it is often convenient to start by loading the ageing oven with one-half of the prepared specimens and performing measurements after the second or third exposure cycle of the recommended series.
Methods based on mean values of normally distributed test results 3 3. In some cases for example, very thick specimenstimes greater than two days may be necessary to establish a stable value. This standard is concerned only with type 2. Figure 4 — Destructive tests — 602162 of time to end-point 6.
The parameters are referred to as the regression coefficients. 6021-2 thickness is also important because the rate of ageing may vary with thickness. The procedure is carried out numerically, and appropriate statistical tests are introduced. A simplified procedure is available in IEC Before determining the property value, these specimens shall be conditioned by exposure to the lowest level of ageing temperature of the test see 5. A simplified procedure is given in IEC End-points of proof tests are predominantly given in 62016-2 form of fixed values of ieec property.
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. Instructions for an adequate number of specimens are given in IEC NOTE 2 Attention should be given to the recommendation in 5. TC – Evaluation and qualification of electrical insulating materials and systems rss. Further guidance will be found in IEC If such material specifications are not available, a selection of properties and methods for the evaluation of thermal endurance is given in IEC It may arise from inadequate experimental technique for example, oven temperature errors ; such non-linearity may be isc by further testing.
Evaluate the results, as listed in 6. 602166-2 provide uniform conditions, the conditioning of specimens after removal from the oven and before measurement may need to be specified. In such cases, it may be possible to obtain an acceptable result by further testing at a lower temperature.
In this test, a test parameter F is calculated from the experimental data and compared with a tabulated value F 0. This led to the concept of the “Thermal Endurance Profile” TEPincorporating the temperature index, its variation with specified ageing time, and a confidence limit.
A number of recommendations and suggestions, useful in establishing times and temperatures, will be found in Annex B. Ageing procedures and evaluation of test results IEC The application of conventional statistical 602216-2, as set out 6216-2 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.
This approach will provide comparisons among materials but bears a poorer relationship 600216-2 item b to the property values required in normal service.
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Buying standards Lec can buy and download PDF versions of BSI publications, including British and adopted European and international standards, through our website at bsigroup. We accept all major 602216-2 cards American Express, Mastercard and VisaPayPal and bank transfers as form of payment. This publication does not purport to include all the necessary provisions of a contract. The y -values derived are used in the calculations of 6.
NOTE 1 This table is intended primarily for cyclic proof testing and non-destructive tests, but may also be used as a guide for selection of suitable time intervals for destructive tests. The chosen property should reflect, in a significant fashion if possible, a function of the material in practical use.
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Early results of the ageing test may motivate an adjustment of ageing cycles or additional ageing temperatures. If not, the thickness shall be reported. The validity of the model is, therefore, not dependent on the lec stringent condition of a linear relationship between the level of the diagnostic property and the degree of molecular change. The abscissa is usually graduated in a non-linear Celsius temperature scale oriented with temperature increasing from left ifc right.
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These values are intended solely as illustration and may be changed as the work requires. If this rule results in changes of mechanism for example, when a transformation point like melting or softening is exceededthen the maximum exposure temperature will need to be limited.
Since processing conditions may significantly affect the ageing characteristics of 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.
In obtaining the RTI, the systematic errors observed in the determination of TI are to a large extent compensated. In all cases, ageing shall be continued until more than one-half of the test specimens in each group have failed to pass the proof test. 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. Very long specification times may also lead to non-linearity see also Annex A.
However, it is 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. TEP was then abandoned, with the TI and HIC being reported in a way which indicated whether or not the statistical tests had been fully satisfied.
Five of the test groups are placed in the oven at the beginning of the sequence. If the decision to extend the original test programme is taken after its completion, the duration of the complete procedure may become prohibitive.