Abstract
The lightning surge response of 15m height cylindrical conductor which stood vertically on the ground is measured by the direct method. Fast optical measuring systems which have the rise time of 5ns are used in the measurements. The wave shapes of the current and the voltage at the top, at 6m below the top and at the foot of the conductor are measured. All current and voltage are measured simultaneously with the tower top current which enables to obtain the time relationship between them.
An equivalent distributed constant line model of a vertical conductor is developed, which produces the surge response wave shapes close to the actual measurements. One section of distributed constant line whose surge impedance is given by the function of conductor radius and height, is found to express the surge response of a vertical conductor. The surge propagation velocity along the line is given by the velocity of light. The proposed model is found to be applicable for the case of short rising time of the imposed current. But the deviation of the response of this model from the actual one increases with the rising time. The correction factor of the proposed model is derived and expressed by the function of the rising time.
