Voltage-time Characteristics and Observation of Discharge Development in SF6 Using Steep-front Square Impulse and Fast Oscillating Impulse Voltages under Quasi-uniform Field Gap

We describe the sparkover voltage and time (V-t) characteristics and the discharge development process in SF6 at 0.1MPa for quasi-uniform field gaps with steep-front square impulse and fast-oscillating impulse voltages. A square impulse voltage has a very short rise time of 20ns and a fast oscillating impulse voltage has a frequency of approximately 30MHz and rise time of 20ns. Both impulse voltages can be generated up to 10µs. Optical observation in the test gap clarifies the discharge development process. We discuss the difference in discharge development for the square and oscillating impulse voltages.