DC electric field effects during measurements of monopolar charge density and net space charge density near HVDC power lines

The influence of a DC electric field on the measurement of monopolar charge densities using an aspirator-type ion counter and the measurement of net space-charge density using a Faraday cage or filter is examined. Optimum configurations which minimize the effect of the electrical field are identified for each type of instrumentation. It is shown that the influence of a DC electric field on measurement of monopolar space-charge densities with an ion counter can be made negligible when the measurements are performed in the ground plane and oriented vertically or horizontally above the ground plane with an attractive potential applied to the ion counter housing. Measurements of net space-charge density with a Faraday cage appear to be significantly influenced by a large field except when the space charge is predominantly monopolar or when composed of large ions (aerosols) with small mobilities. The optimum configuration for the filter is an above-ground horizontal orientation with the filter housing at ambient space potential