The massive blackout in 22 southern provinces and cities on May 22 raised concerns over the security of the national power grid.

The two-hour blackout occurred when a truck driver was moving a tall tree from the garden of a new urban area in southern Binh Duong province. The tree accidentally collided with a 500kV transmission line linked to the national power grid.

Representatives from Electricity of Vietnam confirmed the outage was the result of violating regulations pertaining to safety corridors near power lines.

It was not the first such incident on the 500kV transmission line, which transmits electricity from the north to the south and vice versa.

Figures from the National Power Transmission Corporation revealed there had been seven cases of safety corridor violations along power lines that affected the national grid. They were chiefly caused by activities such as kite flying or use of vehicles which were taller than permitted levels.

The 2005 Government decree on protecting the safety corridor along power lines requires local authorities to inspect and handle violations.

However, Deputy Director General of Electricity of Vietnam Dang Hoang An told Lao Dong (Labour) newspaper that in some localities, protective measures are not effective.

There are 342 guard stations with 1,500 security guards along the 500kV line. However, security guards at many stations have been found to leave their posts, while firefighting equipment has been stolen from some stations, An said.

Meanwhile, many local authorities complained that they should not be held responsible for protecting the electricity works.

The three men who caused the massive blackout in the south on May 22 are expected to be prosecuted, according to Binh Duong province's police.

The suspects are a truck driver, his assistant and a farmer working at the tree garden.-VNA