We have been investigating the contamination flashover voltage performance of hydrophobic polymer insulators．We have clarified in our companion paper(Part I)to this paper that，if evaluated under heavy fog conditions，their contamination flashover voltages decrease with the increase in core diameter, having a rapid reduction from the core diameter of 26mm to the core diameter of 74mm.

  In this Paper we present the results of our investigation of effect of specimen core diameter on the contamination flashover voltage of a cylindrical polymer insulator under simulated rain conditions. We also compare these results with the results obtained on porcelain and polymer insulators under fog conditions.

  In our investigation，we tested polymer insulators with different core diameters but the same or similar shed shapes. Tests were made using a stiff power source under the simulated rain conditions. Salt deposit densities(SDD)applied were 0.03 and 0.5m/cm²  and non-soluble contaminant deposit density(NSDD)was 0.1 mg／cm² . Contaminated and dried specimens were installed vertically in the test chamber and test voltage was applied. Flashover or withstand within 15 minutes was checked 50％ flashover voltage was obtained by the up and down method．

  The relationship between the contamination flashover voltage and the specimen core diameter is shown in Fig.1. The results are completely different from the results obtained under heavy fog conditions．There is only very gradual reduction but no rapid reduction in contamination flashover voltage with the increase in core diameter. The reason for this is that the flashover of a polymer insulator under simulated rain conditions results from bridging by water streaming between the two adjacent shed tips along the insulator, irrespective of its core diameter.

The results are compared with the results obtained on polymer and porcelain insulators under fog conditions as shown in Fig.2. It can be seen that the contamination flashover voltages of 1arger core diameter polymer insulators under simulated rain conditions are higher than those under heavy fog conditions but the difference is not so large or even marginal for the smallest core diameter transmission line insulators．So testing only under heavy fog conditions may be enough for evaluating polymer insulator shaving larger core diameters, while tests under simulated rain conditions as well as under heavy fog conditions may be necessary for evaluating transmission line insulators having the smallest core diameter.