RASitepu,
I wish to have a deterministic answer for you. Unfortunately insulation coordination is a random stochastic phenomenon that requires a deeper analysis in probabilistic terms. Here is what we could say about this scenario:
• The oh Transmission Line above the condensed steam from the rock muffler will be recombine with the air to form a mix with small amount of contaminants (Chlorine, Sulfate and Silica)and conductive iron particules that facilitate the flashover phase-to-phase and phase-to-ground shield wire.
• The amount of contaminant is relative small compare with the air chemical composition. However, for long term exposure surface deposition are expected.
• It is assumed that the overhead conductor is AL and/or Steel reinforced conductor such as All Aluminium Alloy Conductor (AAAC) and Aluminium Conductor Steel Reinforced (ACSR).
• The temperature of the mixt of steam and air will be higher than other section of the line. However, it is not clear if this contribute significantly to increase the line sag.
• The electric field strength in this area is less than other portion of the transmission line (E0 < 3 km/mm). This makes the line more susceptible to flashover failure in the event of transient overvoltage travelling wave.
Perhaps one way to correlate the dielectric degradation in this portion of the line under the steam muffler is to perform an ultraviolet/ Infrared (UV/IR) inspection to diagnostic if there is any significant reduction in dielectric and thermal degradation with respect of the line none exposed to the condensed steam.
See below a few data that could be used as starting point to guide your engineering decision in this matter.
Good luck
FORE CORONA TEST REFERENCES SEE THE FOLLOWING LINKS:
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