Figure 5 illustrates the breakdown strength (breakdown voltage divided by gap length) versus humidity at 30 kHz. These curves have three linear phases. Only one curve is labeled for clarity. The three phases are: 1. Plateau – small variations in breakdown voltage are observed. 2. Drop – stage exhibiting a very marked reduction in breakdown voltage. 3. Tail – final stage of the curve, occurring after approximately 80% RH, were a large increase in breakdown voltage is observed. If the tail phase is disregarded, there is a general reduction of the breakdown voltage with humidity. The tail section was discovered to be due to the deposition of water film on the electrode surfaces. This film is created by the increased condensation after exceeding 80% RH. A separate experiment was performed by wiping the electrode dry after the chamber had been humidified to the maximum RH and quickly repeating the breakdown voltage measurements. The breakdown voltage for the dried electrode system was seen to be lower than that of the wet electrode. It was observed to be approximately the same magnitude of the minimum breakdown voltage of the drop phase. This demonstrated that the large increase in the breakdown voltage for the tail phase was due to the water film and not due to the humidity of the air gap. Since focus of this project is the effect of humidity on the breakdown voltage, the tail phase is discarded. The other two phases of the VLF curves are discussed in Section 4. Figure 6 shows the breakdown strength versus humidity for an 8 mm gap at frequencies of 18, 30 and 50 kHz. Breakdown voltages for all the frequencies follow the same trend, and include all three phases. The curves illustrate progressive breakdown voltage