IEC 61858-2004 pdf – Electrical insulation systems – Thermal evaluation of modifications to an established wire-wound EIS.
1 Scope This International Standard lists the required test procedures for qualification of modifications of an established electrical insulation system (EIS) with respect to its thermal classification. This standard is applicable to EIS used in wire-wound electrotechnical devices. The test procedures are comparative in that the performance of a candidate EIS is compared to that of a reference EIS, which has proven service experience in accordance with IEC 60791 or has been evaluated by one of the procedures given in the IEC 61857 series. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60172, Test procedure for the determination of the temperature index of enamelled winding wires IEC 60216-5, Electrical insulating materials – Thermal endurance properties – Part 5: Determination of relative thermal endurance index (RTE) of an insulating material IEC 60317, Specifications for particular types of winding wires NOTE Annex A cites several parts relating to the IEC 60317 series. IEC 60505, Evaluation and qualification of electrical insulation systems IEC 60791, Performance evaluation of insulation systems based on service experience and functional tests IEC 61033, Test methods for the determination of bond strength of impregnating agents to an enamelled wire substrate IEC 61857 (all parts), Electrical insulation systems – Procedures for thermal evaluation IEC 61857-1, Electrical insulation systems – Procedures for thermal evaluation – Part 1: General requirements – Low voltage IEC 62114, Electrical insulation systems (EIS) – Thermal classification
3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 electrical insulation system (EIS) insulating structure containing one or more electrical insulating materials (EIM) together with associated conducting parts employed in an electrotechnical device 3.2 electrical insulating material (EIM) material with negligibly low electric conductivity, used to separate conducting parts at different electrical potentials 4 General considerations This standard provides relatively low cost and short-time methods by which the user can make modifications to an established EIS by evaluating a) the impact on the thermal life of the EIS if the thickness of an EIM is changed, b) the compatibility, under thermal stress, of a substituted EIM, c) the compatibility, under thermal stress, of other components used in intimate contact with an established EIS. EIM having different temperature indices (ATE/RTE) according to IEC 60216-5 may be combined to form an EIS having a thermal class that may be higher or lower than that of any of the individual components according to IEC 60505. There may be more than one EIS in a particular apparatus. These EIS may have different thermal classes. The following overview (Figure 1) is a flow chart for guidance in selecting the proper clauses for evaluation.
5 Evaluation of the change of thickness of an EIM 5.1 Samples Representative samples of the established EIS (the reference EIS) and of the EIS with reduced EIM thickness(es) (the candidate EIS) shall be evaluated in accordance with Clause 10. 5.2 Acceptance A candidate EIS that meets the acceptance criteria according to Clause 10 shall be assigned the same thermal class as the established EIS. If the results of the candidate EIS testing are outside the acceptance criteria according to Clause 10, then full thermal ageing in accordance with IEC 61857-1 shall be conducted in order to establish its thermal class. NOTE Full thermal ageing may be accomplished by testing at additional temperatures, according to IEC 61857-1.
6 Substitution of winding wire 6.1 General Substitution of a winding wire evaluated in the established EIS can be made without additional testing when one or more of the following conditions have been met: a) the winding wire conforms to an IEC 60317 specification having the same chemical composition, according to the Annex A groupings, as the winding wire evaluated in the established EIS but is of a different size or shape; b) the winding wire conforms to an IEC 60317 specification having the same chemical composition, according to the Annex A groupings, as the winding wire evaluated in the established EIS and has an equal or higher thermal class; c) the winding wire is a bare conductor insulated with one of the EIM evaluated as part of the established EIS in accordance with IEC 61857-1. The thickness to be used shall be such that the electrical stress per unit thickness is not greater than the stress to which the EIM was subjected during the ageing test. NOTE For substitution of an alternate EIM, refer to Clause 8.