Date of Award


Publication Type

Doctoral Thesis

Degree Name



Electrical and Computer Engineering


Engineering, Electronics and Electrical.




The surface flashover strength of cylindrical and conical solid insulators has been investigated in ultra-high vacuum (< 10('-8) Torr) using DC, AC (60 Hz) and lightning impulse and a combination of a DC and impulse and a DC and AC. In general the DC and the impulse flashover voltages for a fixed length of the insulator are almost the same (within (+OR-)5%) and the AC flashover voltage is lower than the DC and the impulse. The combined DC (+OR-) 1.2/50 (mu)s impulse flashover voltage of cylindrical and conical solid insulators in vacuum is influenced by the applied DC pre-stress. A DC pre-stress causes an increase in the subsequent flashover values of the AC superimposed on DC. In general the flashover voltage of solid insulators are independent of the pressure in the range 10('-8) to 6 x 10('-3) Torr. The effects of ultra-violet (UV) light on the electrical performance of solid insulator in vacuum has been studied. The UV irradiation on solid insulator-vacuum interface degrades the electrical performance of the insulator. A method for calculating the DC surface flashover voltage of cylindrical insulators based on the assumption that the discharge occurs in a layer of desorbed gases from the insulator surface has been proposed. The effect of surface charge accumulation on the field distribution has been studied by assuming different patterns of surface charge distributions. The results showed that for a heterocharge accumulation the electric field is enhanced at both the cathode and the anode electrode junctions and for a homocharge accumulation the field enhancement is on the surface of the insulator away from the electrode junctions. In the case of a positive charge accumulation throughout the surface of the solid insulator, an enhancement in the field is found at the cathode and a reduction in the field value at the anode. The electric field distribution along the solid insulator-vacuum interface is computed and analyzed for a cylindrical insulator with metal inserts, cylindrical insulator placed in recessed electrodes, cylindrical insulator with convex curved edges, cylindrical insulator with concave curved edges and cylindrical insulator with metal inserts and placed in recessed electrodes. The electrode-insulator geometry which gives the best performance has been suggested.Dept. of Electrical and Computer Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1983 .P553. Source: Dissertation Abstracts International, Volume: 44-09, Section: B, page: 2852. Thesis (Ph.D.)--University of Windsor (Canada), 1983.