Power line harmonic radiation in Newfoundland

Recent research strongly suggests that harmonic radiation from electrical power distribution networks in industrialized regions (PHLR) has a significant effect on the occurrence of VLF waves and the energetic electron population in the inner magnetosphere, particularly in the American longitude sector. We have measured the PLHR power radiated into the magnetosphere from typical high voltage power transmission lines in Newfoundland due to unbalanced currents flowing in the lines which return through the ground, at harmonics of 60 Hz up to 4.5 kHz. From measurements of the induced a.c. magnetic field at distances from the lines both small and large compared to the skin depth (typically 1 km at 1 kHz), we have been able to estimate both the amplitudes of these unbalanced harmonic currents (~ 1 mA for frequencies 1–4 kHz) and the radiation efficiency of the lines considered as transmitting aerials. We estimate PLHR radiated powers of order 0.05–0.5 μW per transmission line in a 1 kHz bandwidth around 3.2 kHz. This is probably much too small to stimulate magnetospheric emissions but we expect considerably greater radiated powers in other locations where there are strong single sources of 60 Hz harmonics and also in areas where the power consumption density and hence density of power lines is greater.

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