Space charge measurements downwind from a monopolar 500 kV HVDC test line

Measurements made to determine the concentration of space charge present downwind of an HVDC test line and the influence of wind on the space-charge level are discussed. The instrumentation used to make the measurements is described. The results indicate than an HVDC line in corona can increase the space-charge density downwind. Small-air-ion density decays rapidly with distance downwind from an HVDC line in corona. As distance downwind increases, aerosols become the predominant carrier of the space charge. Near an HVDC linear small-air-ions are the predominant charge carrier. For large downwind distances wind turbulence appears to play an increasingly important role in the space-charge density measured