Low-voltage applications mounted on high-voltage towers may pose a safety problem in the low-voltage network when a flashover occurs over the high-voltage insulators. To study the effects experimentally, a 150 kV system was made available. On a high-voltage tower carrying a cellular phone base station, one phase insulator was shorted to the tower. A current of about 200 A was injected into that phase at a large distance. We measured the current distribution and the relevant voltages in the low-voltage net. The experimental current data agree with EMTP calculations. Appropriate measures to guarantee safety for persons and electronic equipment are discussed.