An engineer operates a drone to inspect high voltage power lines in north China's Tianjin, June 24, 2019. (Photos: Xinhua)

A drone operated by an engineer inspects high voltage power lines in north China's Tianjin, June 24, 2019.

An engineer operates a drone to inspect high voltage power lines in north China's Tianjin, June 24, 2019.

An engineer takes out the drone to inspect high voltage power lines in north China's Tianjin, June 24, 2019.

An engineer operates a drone to inspect high voltage power lines in north China's Tianjin, June 24, 2019.