Radar frequency and transient electrical breakdown in vapor-mist dielectrics

摘要

In a recent DOE/SDI? sponsored study regarding the suitability of vapor-mist dielectrics for high voltage space insulation, some measurements were made of their transient and radar frequency pulse breakdown strength, and also of their ultraviolet absorbance properties. It was found that the electrical strength of vapor-mist was very high for nanosecond risetime pulse voltages, e.g., for a C2Cl4 mist in atmospheric nitrogen, 193 kV withstand voltage was obtained for a 100 nsec pulse applied to a 2 cm gap, which is about three times that for nitrogen alone. At X-band (～8 to 12 GHz) radar frequencies at least 12 kW of power could be transmitted through a transmit/receive cell containing vapor-mist (N2/C2Cl4), whereas with the cell containing atmospheric SF6, only 1.5 kW could be transmitted before voltage breakdown occurred. This is equivalent to at least a three times better electrical strength for vapor-mist. Ultraviolet radiation absorption measurements of several liquids revealed that C2Cl4 for example strongly absorbs ultraviolet radiation and, for comparison, has an absorbance two orders of magnitude greater than ozone.