The developing mechanisms of the positive corona streamers on the insulation surface affected due to the nanosecond rise time of impulse voltage wave have been studied by using the dust figure method. By applying short rise time of impulse voltage of 12 to 120ns to a needle point where a glass plate is sandwiched in between the needle and plate electrodes, the diameters of the discharge pattern were measured against the relation between rise time and applied voltage. From the experimental results, it is found that irrespective of the positive applied voltage maintaining a constant of peak value the size of circular discharge patterns reduces with increasing the rise time of 12 to 120ns,and also that irrespective of the applied peak voltage being increased from 6 to 12kV the size of circular discharge patterns holds a constant in the range of the rise time of 12 to 120ns. It is concluded that the experimental results are strongly depending on the Fractal character because the circular discharge patterns recorded are decided due to the charge quantities accumulated at the tip of needle just before the initiation of corona streamer.

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Equivalent circuit model of the electric double layer capacitor (EDLC) represented by series RC elements is simple but useful one commonly used for the analysis and simulation of electric behavior of EDLC, where R is the equivalent series resistance and C is the capacitance. To estimate the value of this capacitance C, a simple method based on the electrostatic relationship between charge Q and voltage V, Q=CV, has been developed so far (charge method). But, considering the voltage dependence characteristic of capacitance C, we have to examine carefully the accuracy of this measurement method, especially for the case of large capacity EDLC. Through the discussion and analysis of the discharge characteristic curve of EDLC, we developed a simple but accurate method (energy method) based on the energy equation which includes the Ohmic loss generated at the resistance R during discharging, and made comparison between the charge method and the energy one to get a conclusion that the proposed method is accurate enough to be able to apply to any EDLC with voltage dependent capacitance. Many test results verified the appropriateness and superiority of the proposed method over the previous one in terms of accuracy.

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