DIN IEC/TS 60216-7-1:2014-04 - Draft

The existing procedures of the IEC 60216 series for the determination of thermal endurance of an electrical insulation material can be time consuming. These methods are therefore of limited use during development of new materials or screening of existing products for use as a material in an electrical insulation. There is an important demand from industry for rapid test methods for the determination of relative thermal endurance (RTE)/temperature index (TI) and halving interval (HIC) to reduce project times and cost. A short-term test procedure for conventional thermal endurance characterization had been proposed in IEC 60216-5 and a simplified approach to data processing is described in IEC 60216-8. Non-conventional methodology for thermal endurance characterization which can reduce further test times is considered in this document. The basic procedure is based on thermal analysis methods (DSC and TGA in particular, but not restricted to them) to evaluate the activation energy of the thermal degradation of the material. The activation energy is directly correlated with the HIC of the thermal endurance. With this information, a single-point thermal endurance test, according to IEC 60216-1 and IEC 60216-5, at the highest temperature of those selected for the conventional thermal ageing procedure, is sufficient to calculate the temperature corresponding to a selected life, typically 20 000 h, that is an estimate of TI. However, due to the inherent uncertainty associated with this analytical approach, only a relative temperature index can be determined for material characterization. This is obtained performing the single-point thermal endurance test in the same conditions of temperature and environment as a reference material of known thermal endurance characteristics that is TI and HIC. The analytical test methods described in this technical specification can satisfy the demand of shortening the insulating material characterization procedure, if used with care and considering the restrictions this method implies. At present, the universal applicability and the accuracy of these methods is not validated, thus a round robin test is required to provide an IEC standard based on these procedures. This part of IEC 60216 is therefore published as a technical specification. IEC 60216 covering the determination of thermal endurance properties of electrical insulation materials consists of several parts: Part 1: Ageing procedures and evaluation of test results; Part 2: Choice of test criteria; Part 3: Instructions for calculating thermal endurance characteristics; Part 4-1: Ageing ovens - Clause 1: Single-chamber ovens; Part 4-2: Ageing ovens - Clause 2: Precision ovens for use up to 300 °C; Part 4-3: Ageing ovens - Clause 3: Multi-chamber ovens; Part 5: Determination of relative thermal endurance index (RTE) of an insulating material; Part 6: Determination of thermal endurance indices (TI and RTE) of an insulating material using the fixed time frame method; Part 7-1: Accelerated determination of relative thermal endurance using analytical test methods (RTEA) - Instructions for calculations based on activation energy; Part 8: Instructions for calculating thermal endurance characteristics using simplified procedures. This series can be expanded. With respect to revisions and new parts, the currently valid catalogue of IEC publications shall be referred to for an in-time listing. This technical specification describes the procedure for the evaluation of the thermal endurance of electrical insulating materials, based on thermal analysis methods for the evaluation of the activation energy of the thermal degradation reaction and a conventional life test providing a life point in the thermal endurance graph. The purpose of this test procedure is to estimate the relative temperature index (RTE). Predictions of thermal endurance based on this procedure are limited to ageing reactions where one single reaction is predominant and directly correlated to the end-point criteria for a specific application. The responsible body is DKE/K 183 "Bewertung und Qualifizierung von elektrischen Isolierstoffen und Isoliersystemen" ("Evaluation and qualification of electrical insulation materials and systems") of the DKE (German Commission for Electrical, Electronic and Information Technologies) at DIN and VDE.