Rotating brownouts loom

Manila Bulletin

By MYRNA M. VELASCO

March 27, 2011, 6:56pm

Earth Hour – Members of the environment group Greenpeace hold lanterns bearing environmental messages Earth Hour Saturday, March 26, 2011.

MANILA, Philippines -- Fears of rotating brownouts this summer were raised following the tripping of the San Jose-San Manuel transmission line of the National Grid Corporation of the Philippines (NGCP), causing power outages in Metro Manila and nearby areas despite the relatively low demand for electricity last Saturday.

The brownouts lasted from 2 p.m. to 5 p.m.

A day after the incident, system operator NGCP was still clueless on what caused the line to trip which triggered massive power loss, primarily in Metro Manila and neighboring areas.

“It is too early to say whether the tripping is a function of overloading or not. We will just have to wait for the report,” NGCP spokesperson Cynthia Alabanza said, stressing that their technical people are still investigating the incident.

Power industry players are apprehensive over the reliability of the transmission system with the power line tripping with relatively low demand. They are also fidgety as to the implications of such incident especially during the summer months when demand for electricity picks up.

Alabanza argued that “overloading” could not have been the only cause of the tripping, as she indicated that even falling trees or storm-tossed tree branch crashing on a transmission line may trigger a line tripping and consequent power outages.

She pointed out that in the case of the brownout incidents triggered by the San Jose-San Manuel line, the initial efforts “were focused on putting the three downed transformers back online.”

As of yesterday, NGCP reported that the lines have already been fully energized.

Meanwhile, Manila Electric Company external communications manager Joe Zaldarriaga explained that “if there is a transmission constraint, there is no other recourse but for us to undertake load shedding which results in rotating power interruptions to balance the system.”

Meralco said it implemented manual load dropping (MLD) for three hours following information transmitted by NGCP on the tripping of its line.

The Department of Energy (DoE) noted that it will look into the matter, as it stressed that “this incident is isolated and need not be interpreted as summer brownouts.”

The tripping of the NGCP line, which is a crucial transmission backbone for power supply to Metro Manila, caused the shutdown of some power plants – mainly the Sual 2, Masinloc, San Roque 3, and Pantabangan generation facilities.

Earlier, the DoE said it was confident there would be no rotating brownouts this summer if generating capacity and demand for power are the only considerations.

But it conceded that transmission constraints and technical glitches could trigger power outages.