National Grid Corp. of the Philippines placed Luzon on yellow alert Thursday because of thin power reserves amid high demand as temperature peaked this year. "Luzon grid on yellow alert from 1 p.m. to 3 p.m. Luzon grid is on yellow alert due to the unexpected shutdown and limited generation of power plants," NGCP said in an advisory. Luzon's available capacity was placed at 10,740 megawatts, versus peak demand of 9,654 MW. Among the plants that went on forced outage were Makban unit 5 (55 MW) SLPGC Unit 1 (135 MW), SLPGC Unit 2 (150 MW), San Gabriel (420 MW), Malaya unit 2 (320 MW), Ilijan Block A (600 MW) and Makban 1 (60 MW). Three plants―Makban unit 5, SLPGC unit 1 and SLPGC unit 2―went on emergency shutdown because of turbine vibration. The San Gabriel plant suffered excitation problem while Malaya 2 reported boiler tube leak.