A City Power contractor has been arrested for allegedly sabotaging a substation in Johannesburg and nearly killing technicians working on the same network nearby.

According to City Power CEO Tshifularo Mashava, the man was found inside a switching substation in the Roodepoort area with working equipment.

The act of sabotage nearly killed City Power operators and technicians working on the network downstream from the same switching station, said Mashava.

"While City Power operators were working on the repairs in the Roodepoort area, they isolated the switching substation for safety purposes.

"By sheer luck, they tested the cables and other infrastructure again before starting their work, only to find that the cables were still live.

"They went back to the transmission station to check how the cable they isolated earlier is suddenly live," she said.

It was at this time that they discovered the contractor had accessed the switching substation.

"The community had already captured him on suspicion that he was there to vandalise and steal the equipment.

"He confessed that he switched on the breakers and could not produce any job card requiring him to be there, nor could he explain his actions," Mashava said.

She said how the contractor gained access to the switching substation remains unclear.

The contractor was taken to the Roodepoort police station. He is expected to appear in court on Thursday.

He is expected to face charges relating to tampering with essential infrastructure and vandalism. He may also face attempted murder charges for putting the technicians' lives in danger, said Mashava.

She added that it has yet to be established if he had any accomplices.

In the past month, there had been at least 100 incidents around Roodepoort where mini substations were vandalised and cables and fuses stolen. These had led to widespread outages, said Mashava. At least seven mini substations had been replaced in the past two weeks.

"We have been experiencing a blatant attack on our infrastructure across the city, with Roodepoort area the hardest hit. Some of the vandalism on the infrastructure cannot be explained as often nothing is taken.

"Most are really bordering on sabotage and we have increased surveillance in collaboration with the SAPS and other security apparatus to ensure we root out the criminals," said Mashava.

"We have never ruled out the involvement of contractors and some of our staff in some of these actions."