Ausgrid is urging people to stop risking their lives by interfering with live electrical wires.
The warning has been issued after would-be thieves used bolt cutters to cut down live high-voltage power lines.
A recent attempted copper wire theft cut power to 770 homes and businesses in Lake Macquarie on Wednesday.
The incident caused two power outages for customers in parts of Carey Bay, Kilaben Bay and Toronto from 2:55am until about 7:30am.
When emergency crews arrived to investigate, they found about 150m of copper cable coiled on the ground and power lines dangling from poles with cable cutters still attached.
Ausgrid chief operating officer Trevor Armstrong condemned the behaviour in the strongest possible terms.
“These were high-voltage live power lines carrying 11,000 volts, so not only is this attempted theft brazen it is also incredibly risky,” Mr Armstrong said.
“The people behind this not only put their own lives at risk they also endangered the public as well.
“This could have ended tragically for the alleged thieves and we were very fortunate that no one was injured, no amount of copper is worth your life.”
Power was safely restored to all customers and the damaged power lines have been replaced.
Ausgrid security and the police are investigating the theft.
Locals who saw any suspicious activity in the area off Awaba Road in Toronto near Ausgrid’s Toronto West zone substation in the early hours of yesterday morning are urged to contact Crimestoppers on 1800 333 000.