DESIGN OF LARGE-CIRCLE ROGOWSKI COIL FOR MEASURING LIGHTNING CURRENT IN BUILDING COLUMNS AND GIRDERS

When observation of a direct lightning strike to a building is perform ed or in an experiment for applying lightning using a building, one ne eds current sensors that can measure the current in building columns, girders, and waifs. As the current sensor, the Rogowski coil commonly is used. The coil is placed around the object to be measured, and the inductive voltage is obtained. Although there are many commercially av ailable units, these sensors are too small for measuring building colu mns and girders. This paper studies Rogowski coils which are long enou gh to encircle the building columns and girders and flexible enough to set up the structure according to the practical situation. First, the coil and the integrator are described by their lumped element equival ent circuits. In addition, the target values were set for the frequenc y bandwidth and the sensitivity. A structure optimum for these charact eristics was found. From the results, a hollow core coil using a vinyl pipe was fabricated. A Rogowski coil 1 to 10 m long was realized whic h has a frequency of 300 kHz and a current-voltage conversion factor o f 1/100. Further, the position dependence of the current to be measure d was observed. Sufficiently practical characteristics were obtained w ith the present coil with a long structure.