Investigation of Space Charge in High-Density Polyethylene Using Thermal-Pulse Response

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Abstract
The thermal-pulse technique for the direct probing of space charge in dielectrics was modified for measurement under short-circuit conditions. The new technique was applied to polyethylene (PE) doped with impurity (antistatic agent), and proved to be effective in outlining the behaviour of the space charge in PE. A positive hetero space charge is formed near the cathode on the application of voltage. With increasing applied field, the total amount of space charge increases and its centroid shifts to the cathode. The electric field at the cathode becomes 1.6–1.7 times as large as the average field. The steep increase of current in the current-voltage characteristics is thought to be closely related to this field enhancement.