Airborne particles and ion concentration levels in the environment of a strong corona ion emitting source

Abstract

Corona ions are generated during electrical discharges which may occur around high voltage infrastructures such as powerlines and substations (Abdel-Salam et al. 2001). Interactions between these emitted ions and airborne aerosols produce charged particles, which are carried to in the wind and depending on the prevailing meteorological conditions, their presence may be observed some distance at some distance from the ion emitting source. While numerous studies have been conducted on corona emissions by high voltage powerlines (HVPLs) and their effect on the earth’s natural dc electric field (e-field) (Bracken et al. 2005; Maruvada 1981a), no attempt has yet been made to characterise or investigate possible associations between parameters characterizing the electrical environment around strong corona ion emitting sources such as electricity substations. This paper presents a study characterizing an environment near a strong corona ion emitting source - an electricity transmission voltage substation. For the purpose of this study, the transmission voltage level is defined as being between 220 and 330 kV. In the proximity of this source, measurements were made of aerosol particle charge, particle number, net space charge and vertical dc e-field. Possible associations between measured parameters and the effects of meteorology (wind) were statistically investigated using the Pearson correlations. The strength of the regressions was tested using the coefficient of determination R2, while statistical significance was asserted at the 5% confidence level. Results of the study showed corona space charge concentration levels and their associated effect on dc e-field decreased with distance from the source. Average net particle charge concentration in the environment of the strong corona source was three times higher than that of an urban outdoor air and about seventeen times that of a mechanically ventilated room (Figure 1). Investigation of links between parameters measured in the environment of the corona ion source revealed the existence of a statistically strong (r = 0.86), and highly significant association (p < 0.05) between aerosol particle charge concentration and ion concentration. A 57% (p<0.05) statistically significant correlation was found to exist between aerosol particle charge and the observed charge in the local dc e-field (mean value of -285 ± 51 Vm-1). Fig 1 Mean and standard deviation (σ) of aerosol particle charge concentration for three different air environments No statistically significant relationship (R2 = 0.6%, P<0.05) was found between aerosol particle charge concentration and aerosol particle number concentration which had a mean value of (3.8 ± 0.445) x 103 (J-Fatokun et al. 2007). This work was supported by the Australian Research council (ARC) funded Linkage project with industry (Project identification number LP0562205). Abdel-Salam, M. and E. Z. Abdel-Aziz (2001). 'Corona power loss determination on multi-phase power transmission lines.' Electric Power Systems Research 58(2): 123-132. Bracken, T. D., R. S. Senior, et al. (2005). 'DC electric fields from corona-generated space charge near AC transmission lines.' IEEE Transactions on power delivery 20(2): 1692-1702. J-Fatokun, F. O., E. R. Jayaratne, et al. (2007). 'Investigation of the associations between parameters characterizing the electrical environment near a strong cocona ion emitting source.' Paper Submitted to the Journal of Atmospheric Environment. Maruvada, P. S. (1981a). 'Corona generated space charge environment in the vicinity of HVDC transmission lines.' IEEE Transactions on Electrical Insulation EI-17(2): 125-130