Laboratory Measurement of Impulse Voltages

A brief description is given of impulse generators and the discharge circuit constants involved in obtaining impulse voltages of the desired wave shapes. The relative influences of these constants are recognized and simplified discharge circuits are given. The variations in the wave shape and the reasons for the differences in sparkover values obtained with the three test waves, ½/5, 1/10 and 1½/40, are discussed. The degree of accuracy of the sphere gap for use in measuring impulse voltages is outlined. The resistance-capacitance and the resistance-cable voltage dividers for the connection of the cathode ray oscillograph are described and their operation analyzed in detail. Both dividers are shown to be satisfactory when properly arranged. Data are given showing that the same kilovolts per millimeter on the oscillogram for widely different wave shapes can be obtained. A specimen table for recording of complete test data is suggested which, it is thought, will tend to eliminate a lack of uniformity and completeness in data previously reported.