Understanding Electrical Tracking Resistance Tests: IEC 60112 vs IEC 60587
- Dunel Atlantic
- Aug 12
- 2 min read
Two IEC standards define the evaluation of surface tracking resistance of solid insulating materials under contaminated conditions:
IEC 60112 – Determination of the proof and comparative tracking indices (CTI/PTI)
IEC 60587 – Evaluation of resistance to tracking and erosion under severe ambient conditions
Although both standards address electrical tracking phenomena, they represent fundamentally different stress levels and are not interchangeable.
IEC 60112 – Comparative Tracking Index (CTI)
• Contaminant: 0.1 % NH₄Cl solution, applied as 50 drops at 30 s intervals
• Electrodes: platinum, gap 4.0 mm
• Test voltages: stepwise increase from 100 V to a maximum of 600 V
• Specimen orientation: horizontal
• Duration per voltage level: typically < 10 minutes
• Performance index: CTI value (highest voltage withstood for 50 drops without tracking)
• Primary failure mode evaluated: formation of conductive path (tracking)
• Typical field of application: insulating materials for low-voltage equipment (≤ 1 kV), indoor or conditionally protected environments
IEC 60587 – Tracking and Erosion under High-Voltage AC Stress
• Contaminant: NH₄Cl solution (0.01–0.1 %), applied as a continuous flowing film
• Specimen inclination: 45° ± 5°
• Electrodes: stainless steel
• Test voltages (fixed): 1.0 / 2.5 / 3.5 / 4.5 / 6.0 kV rms (50/60 Hz)
• Duration: 6 hours per voltage level
• Acceptance criteria:
– No continuous conductive path
– Erosion depth limited
– Leakage current shall not exceed 60 mA for > 2 s
• Classification: Method 1A followed by voltage level passed (e.g., 1A 4.5, 1A 5.0)
• Primary failure modes evaluated: tracking and material erosion by sustained arcing
• Typical field of application: polymeric insulators, bushings, surge arresters, and cable accessories for outdoor service in medium- and high-voltage networks (≥ 10 kV nominal system voltage)
Key Technical Differences (text table – blog-safe)
Contaminant application → IEC 60112: Intermittent drops (50) | IEC 60587: Continuous flowing electrolyte
Electrolyte concentration → IEC 60112: Fixed 0.1 % | IEC 60587: Adjustable 0.01–0.1 %
Test voltage range → IEC 60112: 100–600 V | IEC 60587: 1.0–6.0 kV
Electrode material → IEC 60112: Platinum | IEC 60587: Stainless steel
Specimen inclination → IEC 60112: Horizontal | IEC 60587: 45°
Duration → IEC 60112: Minutes per step | IEC 60587: 6 hours continuous
Failure mechanisms assessed → IEC 60112: Tracking only | IEC 60587: Tracking + erosion
Environmental severity simulated → IEC 60112: Light intermittent pollution | IEC 60587: Severe continuous wet contamination
Selection Criteria – Technical Requirement Driven
• IEC 60112 is the appropriate standard when the service voltage is ≤ 1 kV and the material operates in controlled or indoor environments.
• IEC 60587 shall be specified when the insulating component is exposed to system voltages ≥ 10 kV in outdoor or heavily polluted industrial environments, where continuous wetting and high electric stress coexist.
Modern high-performance outdoor insulation systems (e.g., HTV silicone rubber, cycloaliphatic epoxy, glass-fibre reinforced resins) are routinely qualified to both standards:
– CTI ≥ 600 V (Material Group I per IEC 60695-11-10)
– IEC 60587 minimum 1A 4.5, with premium formulations achieving 1A 5.0 or 1A 6.0
Correct application of these standards is essential for reliable long-term performance and compliance with international specifications for electrical power equipment.
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