Experimental measurement, analysis and prediction of electric and magnetic fields in open type air substations

In this paper, the electric and magnetic flux density values in open type air substations are analyzed. For this reason, an extensive measurement survey was conducted to identify potential large sources of electric and magnetic fields within seven 132/11 kV open type air substations always having them compared with the International Commission Non Ionizing Radiation Protection (ICNIRP) safety guidelines published in 1998. The maximum electric and magnetic flux density values obtained in the open air circuitry units are found to be 7696 and 7306.5 V m−1 and 45.89, 38.11, 35.30 μT, which are 1.30, 1.37, and 10.9, 11.3, 14.1 times below the safety guidelines of the ICNIRP. In one of the coil rooms, the magnetic flux density was found to be 6.26 times above the safety guidelines, constituting an immediate threat to working personnel of the substation. Furthermore, a simplistic theoretical methodology based on experimental measurements is proposed that establishes a linear correlation between the transformer current and the maximum magnetic flux density based on Biot–Savart law, provided that the distance from the source remains constant, to predict the magnetic flux density by extrapolation to the permitted and nominal currents and compare them to the safety guidelines of the ICNIRP.

► It measures the three-dimensional magnetic flux density of substations.
► Proposes a simplistic theoretical methodology based on experimental results.
► Establishes a linear correlation between current and maximum magnetic flux density.
► Extrapolates to predict magnetic flux density exposures close to transformers.