Comparisons of ground level measurements of ion concentration and potential gradient upwind and downwind of HV power lines in corona

Simultaneous ion concentration and potential gradient measurements were made at AC high voltage power lines using ion mobility spectrometers and electric field mills. A significant (p < 0.01) change in central tendency and variability of ion concentration and potential gradient can occur downwind of power lines. In 3 out of 8 downwind measurements, there was a discrepancy of sign between the overall mean of these quantities, attributed to ion dispersion and ion–aerosol attachment. While ion concentrations give a greater indication of personal exposure, potential gradient measurements are more appropriate for assessment of the behaviour of a power line.