The Electricity Generating Authority of Thailand (Egat) on Wednesday apologised for the massive power blackout in 14 southern provinces on Tuesday night and explained how it happened.
“Egat would like to apologise to the people for this incident. We have ordered an inspection of all electric power transmission lines to the South to prevent a repeat of it,” Egat governor Suthat Patmasiriwat told the media.
Mr Suthat said two 500-kilovolt (kV) transmission lines and two 230-kV lines were used to supply electricity from the Central Plains to the southern region. At 8am on Tuesday, one of the 500-kV lines was discharged from the system for maintenance. At 5.26pm, lightning strikes were believed to have been the cause of a malfunction in the other 500-kV line, which led to a shortfall in the grid.
As a consequence, authorities were forced to increase power transmission through the 230-kV lines, which have less overload capacity. The cables later malfunctioned due to overload.
Demand for electricity in the South on Tuesday peaked at 2,200 megawatts, while local power plants were generating 1,600 MW. Electricity supply from the four main power plants in the region — in Nakhon Si Thammarat, Songkhla, Krabi and Surat Thani provinces – were discharged from the system automatically for safety reasons after the power fell below the standard 50 Hz grid frequency, Mr Suthat said.
After the blackout, Egat ordered all its power plants in the South to boost electricity generation to full capacity. That included power generation by diesel plants in Surat Thani province. Egat also bought 200 MW of electricity from Malaysia. Power supplies were restored to all households by 11pm, the Egat governor said.
The Egat board of directors on Wednesday ordered a committee be set up to investigate the power outage and report its findings within seven days, staring on Thursday.