Comparative Tracking Index (CTI) - UL 746
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.
|Tracking Index (V)||PLC|
|600 and Greater||0|
|400 through 599||1|
|250 through 399||2|
|175 through 249||3|
|100 through 174||4|