The ASTM standard for Comparative Tracking Index (CTI) is ASTM D3638. The CTI test is used to evaluate the electrical tracking and erosion resistance of solid electrical insulating materials. It measures the resistance of these materials to surface tracking and erosion under specified test conditions.
The ASTM D3638 standard provides the test method and procedures for determining the CTI of insulating materials. The test involves applying a voltage to a set of electrodes on the material surface and subjecting it to a conducting contaminant solution. The test assesses the time taken for the material to form a conducting path between the electrodes, indicating its resistance to electrical tracking.
The CTI value is usually represented as a voltage level, such as CTI 100, CTI 175, etc. It indicates the voltage at which 50% of the test specimens would fail within a specified time frame. A higher CTI value indicates better tracking resistance and a higher level of safety for electrical applications.
The ASTM D3638 standard ensures consistent and reliable testing procedures for the CTI of electrical insulating materials, allowing manufacturers and users to evaluate and compare the electrical performance of different materials.