Comparative Tracking Index (CTI)

UL 746, IEC 60112

Comparative tracking index (CTI) is used to assess the relative resistance of insulating materials to tracking. The CTI expressed as that voltage which causes tracking after 50 drops of 0.1 percent ammonium chloride solution have fallen on the material. The results of testing the nominal 3 mm thickness are considered representative of the material’s performance in any thickness.

The voltage which causes tracking after 50 drops of 0.1% ammonium chloride solution have fallen on the material. The results of testing at 3 mm thickness are considered representative of the material’s performance in any thickness.

Tracking is an electrical breakdown on the surface of an insulating material. A large voltage difference gradually creates a conductive leakage path across the surface of the material by forming a carbonized track. Performance Level Categories (PLC) were introduced to avoid excessive implied precision and bias.