Development and field testing of a vertical-aerial lightning-flash counter

A vertical-aerial lightning-flash counter has been developed to replace the CIGRÉ counter, which has a horizontal aerial. Using one-tenth scale models, the relative open-circuit voltage of the two types of aerial, and their capacitances, were measured for various lengths of vertical aerial. A procedure for designing the filter circuit of the vertical-aerial counter, and for selecting the optimum vertical-aerial length was based on the results of the model tests. The objective was to ensure that the frequency response and threshold of the vertical-aerial counter were the same as those of the CIGRÉ counter. Field tests have been carried out, between 1972 and 1974, at three stations in southeast Queensland, one of each type of counter being installed at each station. Various lengths of vertical aerial, two types of aerial insulation and two filter circuits have been used. The circuit currently recommended, used with an aerial length of 3.3 m, gives registrations within 10% of those of the CIGRÉ counter when averaged over several thunderstorms, which is considered satisfactory. As a guide to installation requirements, the effect of nearby obstructions on the open-circuit voltage of both types of aerials was also measured.