Sparkover in Mixtures of Air and Water Vapor

Tests at 100°C, where large amounts of water vapor can be present in air, indicate that the effect of water vapor on sparking voltage depends on the type of sparking. In the relatively uniform field between sphere gaps the sparking voltage is found to increase by about 6 percent when the water vapor content of air is increased from 0 to 5 percent by volume. However this sparking voltage increases by only an additional 5 percent (to 11 percent) when the water vapor content is increased from 5 to 25 percent. However sparkover voltage of a one-inch gap in a non-uniform field and resulting from successive pulsed discharges shows a slighty smaller increase (5 percent) when the water vapor content is increased from 0 to 5 percent but doubles when the water vapor content is increased from 5 to 25 percent.