Tracking Index Apparatus For Electrical Lab Training

Tracking Index Apparatus - For Electrical Lab Training Breakdown of any insulating material generally occurs either through its volume or over its surface, or in both ways. Surface failures may arise from flash over, or from progressive degradation of the insulation surfaces by small localized sparks. Such sparks are the result of breaking up of a surface film of conducting contaminant on the insulation by the heat of a leakage current passing through it. Rapid breaks in the leakage current produce an over-voltage at the site of the discontinuity and an electric spark is caused. Repeated sparks at any one point may lead to setting up of a carbon track between points at different potentials. This process is known as Tracking. Insulating parts retaining live parts in position shall have adequate resistance to tracking if they are exposed to excessive deposition of moisture or dirt in normal use. The test chamber is placed on the side of a sheet metal control panel which houses various voltage and current controlling elements, besides switches, indicators, drop counter, etc. The control panel is fitted with an auto transformer (variac) to vary the voltage across the electrode and a rheostat to adjust the resistance in the circuit to limit the current to 1 ampere with the electrodes short circuited, and a drop counting circuit with an electronic digital counter to count the number of drops. It is also fitted with a digital voltmeter, a digital ammeter, and various switches and indicators. A thermal relay is provided to trip off the supply to the electrodes and to activate an audio-visual alarm as soon as the breakdown of the insulation occurs.