IEC 61858-2:2014

IEC 61858-2:2014 Overview

IEC 61858-2:2014 is an international standard that defines the thermal evaluation procedures for modifications to an established electrical insulation system (EIS), specifically focusing on form-wound EIS used in electrotechnical devices. This part of the IEC 61858 series provides comparative test methods to assess how changes in an EIS affect its thermal classification, ensuring reliability and safety in electrical insulation systems. The standard emphasizes comparing the performance of a candidate EIS against a reference EIS with proven service experience following IEC 60505 or validated by IEC 60085 and IEC 60034-18-31.

By following IEC 61858-2, manufacturers and engineers can confidently qualify changes such as substitutions, additions, or thickness modifications in the insulation system, maintaining the quality and durability essential for high-performance electrical machines.

Key Topics Covered

• Thermal Classification and Evaluation: Establishes test procedures to assess thermal endurance and ranking of modifications to form-wound insulation systems.
• Comparative Testing Framework: Candidate EIS materials or components are evaluated relative to a reference system with established service history.
• Scope of Modifications: Includes substitution of phase or ground insulation layers, winding wire, and impregnating resin or varnish; evaluation of additives; and thickness adjustments.
• Specific Procedures:
  • Procedure C: Single-point thermal aging test to determine relative thermal endurance index (RTE)
  • Procedure D: Full thermal aging test for comprehensive thermal classification validation
• Relevant Materials: Focuses on rectangular winding wires, impregnating resins, and additives used within form-wound coils.
• Normative References: Incorporates related standards such as IEC 60085 (Thermal Evaluation), IEC 60034-18-31 (Thermal Classification for Form-wound Windings), and IEC 60317 series (Winding Wire Specifications).

Practical Applications

IEC 61858-2 is essential for professionals involved in electrical machine manufacturing, quality assurance, and product development:

• Form-Wound Coil Manufacturing: Ensures thermal integrity when changing insulation components during winding, impregnation, or finishing stages.
• Electrical Machine Design: Helps designers verify insulation suitability for thermal stress in motors, generators, transformers, and other electrotechnical equipment.
• Material Qualification: Aids materials engineers in qualifying new wire enamel coatings, resin formulas, or insulating fillers without compromising thermal ratings.
• Quality Control and Compliance: Provides manufacturers with standardized testing to demonstrate product safety and conformity with international thermal endurance requirements.
• Reliability Improvement: Supports maintenance of thermal longevity and prevention of insulation failure due to overheating by rigorous testing of modified systems.

Related Standards

• IEC 60505: Evaluation and qualification of electrical insulating materials and systems – foundational principles referenced in IEC 61858-2.
• IEC 60085: Electrical insulation – Thermal evaluation and designation – core thermal classification guidance.
• IEC 60034-18-31: Functional evaluation of insulation systems for rotating electrical machines – specific to form-wound winding applications.
• IEC 60216 Series: Thermal endurance properties of electrical insulating materials – details methods for determining thermal ageing indices.
• IEC 60317 Series: Specifications for particular types of winding wires – critical for wire material standardization in form-wound EIS.

By adhering to IEC 61858-2:2014, stakeholders in the electrotechnical industry ensure that modifications to insulation systems uphold thermal performance standards, thereby enhancing machine reliability, performance longevity, and operational safety. This standard is key in the qualification and certification processes of form-wound electrical insulation systems in motors, generators, transformers, and related applications.