What are the common sources of ELF radiation?
Singapore's power transmission grid operates at 50 Hz. Hence, electrical equipment and cables emit ELF magnetic fields at this frequency. The strength of the ELF radiation level is proportional to the current within the electrical equipment and cables – the higher the current (within the electrical equipment and cables), the stronger the ELF magnetic field.
The common sources of ELF magnetic fields include electrical switchrooms, electrical substations, common household electrical appliances (i.e. washing machine, vacuum cleaners), electrical distribution box, etc.
The table below shows the ELF magnetic field levels at 30 cm away from the various electrical appliances, which provides a useful gauge of the common ELF magnetic field levels.
| Appliance |
Range (µT) |
| Electric oven | 0.15 - 0.5 |
| TV | 0.04 - 2 |
| Washing machine | 0.15 - 3 |
| Hair dryer | 0.01 - 7 |
| Electric shaver | 0.08 - 9 |
| Vacuum cleaner | 2 - 20 |
From: The World Health Organisation; Readings at 30 cm distance
What are the ELF levels in Singapore?With the support from the Energy Market Authority and the SP Group, the NEA has conducted measurements of the ELF levels near selected electrical substations (ESS).
The tables below shows the measurement results for 22 kV and 66 kV ESS. Based on readings, the NEA noted that the
ELF levels do not exceed the ICNIRP guidelines of 100 µT and that the levels decrease with distance from the source (ESS). The NEA noted that elevated ELF levels could be experienced at places directly above underground electrical cables or near electrical equipment (within the ESS).
|
Distance from the ESS building (m)
| Avg Readings (µT) for 22 kV ESS |
Locations directly above udg. cables | Other locations |
| 1 | 0.239 | 0.138 |
| 3 | 0.108 | 0.068 |
| 5 | 0.080 | 0.060 |
Average Readings (μT) for 22 kV ESS
|
Distance from the ESS building (m)
| Avg Readings (µT) for 66 kV ESS |
Locations directly above udg. cables | Other locations |
| 1 | 1.868 | 0.287 |
| 3 | 2.289 | 0.146 |
| 5 | 3.262 | 0.108 |
Average Readings (μT) for 66 kV ESS