There is no one way to determine a safe distance from street power lines, but a good range is between 10 to 200 feet from the wires. For high voltage transmission lines with larger cables and tall towers, a safe distance is around 700 feet.
The safe distance from power lines mainly depends on the level and strength of the magnetic fields being emitted from them and the configuration of the power transmission. A gaussmeter may be used to measure this. Exposure to electromagnetic fields must not be higher than 3 milligauss, especially for children, as it increases their risk of having leukemia.