An experimental technique to study space charge injection in polymeric materials under AC voltage

An experimental technique for detecting space charge injection in polymeric material under divergent AC field is described. The automated charge detector can be used for studying charge injection as a function of voltage and time in the 0.001-0.01-pC range. Charge injection is a strong effect above a critical voltage V/sub c/. For a moderate overvoltage, three different phases can be distinguished in the evolution of the dielectric properties: (1) a discharge-free regime, in which low-frequency space charge injection occurs; (2) a transition regime, with high-frequency discharge-like pulses superimposed on the charge injection signal; and (3) an electrical tree propagation regime.<
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