Noise Profile of Wireless Channels in High Voltage Substations

In this survey, some measuring metrics are identified to study the average noise power variations in typical outdoor power substations. Power substations generally have metallic structures and despite the insulation considerations have high electric fields. The physical size of a substation does not allow a completely controlled experiment. A setup plan was arranged to study the noise floor variation in a few substation switchyards in residential, industrial, isolated and sparsely populated subdivisions. The empirical data sets were collected, processed and compared with the known noise constituents that were cited in the literature. A two-week measuring window was chosen to encounter any possible factors that might affect results at several substations. Several field measurements were executed to enable the comparative analysis of the recorded data. By collecting the weather data during the survey, it was illustrated that the average noise floor in the spectrum of interest (i.e. 2.4 GHz), does not correlate or has week correlations with the real time weather condition changes, such as humidity, pressure and precipitations. The analysis suggests that the noise floor variation (and hence the link quality) is time-dependent and has an underlying dominant semi-deterministic constituent in addition to the classical random distribution. This semi-deterministic component is associated with the location of the substation switchyard (e.g. residential or industrial), and its dynamic range is significant and should be identified. The methodology, which is adopted in this study has applications in the analysis of static outdoor environments. Several practical considerations have been discussed in this paper for future implementations in high electromagnetic field environments.