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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It is identical to IEC Together with BS EN A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract.

Users are responsible for its correct application. The British Standards Institution Ageing procedures and evaluation of test results IEC Avenue Marnix 17, B – Brussels?

The following dates are fixed: This edition constitutes an editorial revision where the simplified method has been removed and now forms Part 8 of the EN Series: Instructions for calculating thermal endurance characteristics using simplified procedures. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights.

In the official version, for Bibliography, the following notes have to be added for the standards indicated: For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document including any amendments applies. Determination of thermal endurance properties of electrical insulating materials Choice of test criteria Electrical insulating materials – Thermal endurance properties Part 3: Ageing ovens – Single-chamber ovens Electrical insulating materials – Thermal endurance properties Part 8: Instructions for calculating thermal endurance characteristics using simplified procedures Guide for the statistical analysis of ageing test data Part 1: Accelerated ageing and test procedures were therefore required to obtain the necessary information.

The IEC series has been developed to formalize these procedures and the interpretation of their results. Physico-chemical models postulated for the ageing processes led to the almost universal assumption of the Arrhenius equations to describe the rate of ageing. Out of this arose the concept of the temperature index TI as a single-point characteristic based upon accelerated ageing data.

NOTE The term Arrhenius is widely used and understood to indicate a linear relationship between the logarithm of a time and the reciprocal of the thermodynamic absolute or Kelvin temperature. The correct usage is restricted to such a relationship between a reaction rate constant and the thermodynamic temperature. The common usage is employed throughout this standard.

The large statistical scatter of test data which was found, together with the frequent occurrence of substantial deviations from the ideal behavior, demonstrated the need for tests to assess the validity of the basic physico-chemical model. 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 iev to describe iwc capabilities of materials.

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 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. Consequently, a material may be assigned more than one temperature index, derived, for example, from the measurement of different properties and the use of different end-point times.

It was subsequently found that 602162 statistical confidence index included in the TEP was iwc widely understood or used. 6216-2, the statistical tests were considered essential, particularly after minor modifications to make them relate better to practical circumstances: 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. At the same time, the calculation 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.

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Simultaneously with the development of the IEC series, other standards were being developed in ISO, intended to satisfy a similar requirement for plastics and rubber materials.

These are ISO and ISO respectively, which use less rigorous statistical procedures and more restricted experimental techniques. A simplified calculation procedure is described in IEC 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.

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.

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. For the valid application of the standard, no transition, in particular no first-order transition should occur in the temperature range under study.

Throughout the rest of this standard the term “insulating materials” is always taken to mean “insulating materials and simple combinations of such materials”. IECStandard conditions for use prior to and during the testing of solid electrical insulating materials IECElectrical insulating materials — Thermal endurance properties — Part 2: Determination of thermal endurance properties of electrical insulating materials — Choice of test criteria IEC Instructions for calculating thermal endurance characteristics IEC all Parts 4Electrical insulating materials — Thermal endurance properties — Part 4: Instructions for calculating thermal endurance characteristics using simplified procedures 1 1 ———————— To be published.

Methods based on mean values of normally distributed test results 3 3. Values of the abscissa are proportional to the reciprocal of the thermodynamic absolute temperature. The abscissa is usually graduated in a non-linear Celsius temperature scale oriented with temperature increasing from left to right.

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Ascending order in this standard implies that the data is ordered in this way, the first orderstatistic being the smallest. This standard is concerned only with type 2. The reference level may for example, be a mean value one parameter or a line two parameters, slope and intercept. The parameters are referred to as the regression coefficients. The value of its square is between 0 no correlation and 1 complete correlation. Note 2 to entry: Where there is no risk of ambiguity, either temperature groups or test groups may be referred to simply as groups.

It is strongly recommended that the full evaluation procedure, as described below and in 5. Diagnostic procedures may be non-destructive or destructive determinations of a property or potentially destructive proof tests see 5. The full experimental and evaluation procedures are given in Clause 5 and as far as 6.

A simplified procedure is given in IEC The chosen property should reflect, in a significant fashion if possible, a function of the material in practical use. A choice of properties is given in IEC To provide uniform conditions, the conditioning of specimens after removal from the oven and before measurement may need to be specified.

If such material specifications are not available, a selection of properties and methods for the evaluation of thermal endurance is given in IEC 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.

However, there is often a need for such information related to other longer or shorter times. 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.

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In the same way, the ageing cycle durations should be changed in approximately the same ratio. The temperature extrapolation again shall not exceed 25 K.

In cases of shorter specification times, the related times may be decreased in the same ratio if necessary. Particular care will be needed for very short specification times, since the higher ageing temperatures may lead into temperature regions which include transition points, for example, glass transition temperature or partial melting, with consequent non-linearity. Very long specification times may also lead to non-linearity 6021-2 also Annex A. There are two alternative ways in which the end-point may be defined: This approach will provide comparisons among materials but bears a poorer relationship than item b to the property values required in normal service.

For the determination of idc initial value, see 5. This value might be selected with respect to usual service requirements. End-points of proof tests are predominantly given in the form of fixed values of the property. 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 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.

The material specifications or the test standards will contain all necessary instructions for the preparation of specimens. The thickness of specimens is in some cases specified in the list of property measurements for the determination of thermal endurance. If not, the thickness shall be reported. Some physical properties are sensitive even to minor variations of specimen thickness. In such cases, the thickness after each ageing period may need to be determined and reported if required in the relevant specification.

The thickness is also important because the rate of ageing may vary with thickness. Ageing data of materials with different thicknesses are not always comparable. Consequently, a material may be assigned more ieec one thermal endurance characteristic derived from the measurement of properties at different thicknesses. Screening measurements ensure that specimens are of uniform quality and typical of the material oec be tested.

Since processing conditions may significantly affect the ageing characteristics of some materials, it shall be ensured that, for example, sampling, cutting ifc 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. Instructions for an adequate number of specimens are given in IEC Generally, the following ie 5. It is good practice to prepare additional specimens, or at least to provide a reserve of the original material batch from which such specimens may subsequently be prepared.

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. 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. 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.

For destructive tests, see 5. However, further guidance will be found in IEC 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. Further guidance will be found in IEC