Comparative Tracking Index
The Comparative Tracking Index or CTI is used to measure the electrical breakdown (tracking) properties of an insulating material. To measure the tracking, 50 drops of 0.1% ammonium chloride solution are droped on the material, and the voltage measured for a 3mm thickness is considered representative of the material performance.
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 |
| < 100 | 5 |