IEC 60112:2025

Overview

IEC 60112:2025 - "Method for the determination of the proof and the comparative tracking indices of solid insulating materials" - is the sixth edition of the IEC test method for assessing tracking resistance of solid insulating materials using alternating voltage. The standard defines how to determine the proof tracking index (PTI) and the comparative tracking index (CTI), and includes an optional procedure for evaluating electrical erosion. It is a basic safety publication intended for use by technical committees, test laboratories, materials manufacturers and product designers involved in insulation safety and material selection.

Key topics and technical requirements

• Scope and purpose: Establishes procedures for PTI (acceptance / quality control) and CTI (material characterization / comparison).
• Test voltage limit: Designed for test voltages up to 600 V AC; higher AC or DC voltages reduce test severity and are not covered.
• Specimens and conditioning: Tests are performed on plaques or pieces taken from equipment; environmental conditioning and surface state are required because composition and surface condition directly affect results.
• Apparatus elements: Specifies electrodes, test circuit, dropping device (for contaminant solution), specimen support, and conditioning chamber.
• Pass/fail criteria: PTI is the proof voltage at which five specimens withstand the test; CTI is the maximum voltage at which five specimens withstand 50 drops without tracking failure (with additional information from 100-drop behavior). Persistent flame and tracking failure criteria are defined.
• Erosion assessment: Procedure included when erosion determination is required.
• Terminology change: In this edition the term “resistivity” in clause 7.3 has been replaced by “conductivity” - an important technical revision.

Practical applications and users

Who uses IEC 60112:2025:

• Materials manufacturers - to characterize and compare polymer and insulating formulations (CTI) and to set acceptance levels (PTI).
• Test laboratories - routine testing, calibration and reporting of PTI/CTI results.
• Design and safety engineers - input for insulation coordination and selection of materials for equipment likely to operate under moist/polluted conditions.
• Compliance and quality teams - quality control of fabricated parts and batch acceptance.

Important guidance: Results are not directly suitable for calculating safe creepage distances; they should be used together with insulation coordination principles (considering overvoltage, creepage distances and pollution degree) per IEC 60664-1.

Related standards

• IEC 60664-1 - Insulation coordination for equipment (principles, requirements and tests).
• IEC 60587 - Inclined plane test for materials (more severe, outdoor performance).

Keywords: IEC 60112:2025, proof tracking index (PTI), comparative tracking index (CTI), tracking test, solid insulating materials, alternating voltage up to 600 V AC, erosion, insulation coordination.