Determination of on-the-Spot Occupational Elf Magnetic Field Levels in Hydro-Electric Power Transmission Switchyards

Abstract

The study determined the level of spot ELF magnetic fields generated in switchyards of the Hydro-electric power located in Niger state, Nigeria using the same measurement procedures. Extech 480826 Triple-Axis EMF metre was used for data capturing to assess the intensity of emitted ELF magnetic field. The external probe of Extech 480826 Triple-Axis metre was then mounted on specially constructed stand with three different reference heights that support the sensor in fixed position for field detection and recording at a spot. The stand was usually placed at accessible, permissible and safe locations in segmented manner within the switchyard. The on-the-spot occupational exposure was computed as the mean of the measurements from the three different reference heights of 1.0, 1.5 and 1.8 m above ground level. The mean values of 6.1780 µT was obtained in switchyard of Kainji Hydro-electric power station, 5.7843 µT was obtained for Jebba Hydro-electric power station switchyard while 5.0555 µT was obtained for Shiroro Hydro-electric power station switchyard as their on-the-spot occupational exposure. When the group differences were assessed using Dunnett’s T3 Post Hoc Multiple Comparison test, Kainji switchyard was observed to have significant difference of (p = .027) with Shiroro switchyard, while nonsignificant difference of (p = .606) was observed with Jebba. Switchyards of Shiroro and Jebba show nonsignificant difference of (p = .259). The surveyed and analysed results of the study have revealed that on-the-spot occupational ELF magnetic fields level emitted in the switchyards are not the same within the switchyard and there exist variation from one switchyard to another even though operated at the same frequency of 50 Hz and voltage level of 330 kV.