Richard Harrison wrote:
Flash-overs of the guy insulators occurs in S.E. Texas where the
humidity is often very high by most standards.

http://www.esda.org/basics/part1.cfm

Take a look at Table 2 where humidity is taken into account.
The static voltages at low relative humidity are magnitudes
higher than the voltages at high relative humidity. It certainly
can happen at high humidity but low humidity makes the problem
magnitudes worse.
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73, Cecil http://www.qsl.net/w5dxp