PLN network vulnerable to disruption

The Jakarta Post, Jakarta

State electricity company PLN said the power outages that hit most of Jakarta and its surrounding areas on Thursday evening and Friday morning were caused by "disturbances" in its transmission lines, and dismissed concerns the blackouts were precursors to a power crisis.

PLN, however, has not yet been able to establish the exact cause of the disturbances, saying the outages could be the result of anything from a "simple kite string containing a bit of copper to lightning".

PLN corporate secretary Muljo Adji AG said the company was continuing to search for the cause of the two power outages, which left 4.5 million customers without electricity for hours.

"So far we haven't been able to identify the cause of these disturbances," Muljo said.

PLN attributed the blackout on Thursday evening to a disturbance at its 100-kilometer-long high-voltage transmission line connecting two relay stations in Cibinong, some 50 kilometers south of Jakarta, and Cilegon, some 60 kilometers west of the capital.

Through this line, the two relay stations supply electricity to Jakarta and West Java from power plants in the region and in East Java.

Another disturbance was behind Friday's power outage, this time at the transmission line connecting relay stations in Cibinong and Sigalung, 50 kilometers southeast of Cibinong.

Here too PLN is still searching for the cause of the disturbance, Muljo said.

"The problem with disturbances in transmission lines is that they are hard to detect," he said.

Although the lines are supported by giant steel towers, they can be easily disrupted if something becomes entwined in their high-tension cables.

"It could be the string of a wayward kite that contains a bit of copper or simply lightning," Muljo said.

If the kite string touched two of the tower's three high- tension cables it could cause a short-circuit, and if there was a fire the protection system would immediately cut off the power supply, he explained.

"Meanwhile, there would be nothing left of the string for us to locate."

But when asked how this could have happened at two separate locations at nearly the same time, Muljo could not answer.

He admitted transmission lines were vulnerable and did not dismiss the possibility of sabotage.

"We haven't found any indications of this (sabotage) ... but it's possible."

National Police chief Gen. Da'i Bachtiar, however, ruled out the possibility that sabotage was behind the blackouts.

On Friday afternoon, electricity gradually returned to homes and offices in Jakarta and surrounding towns. But some areas on the outskirts of the capital remained without power into the evening.

Muljo said the disturbances in the transmission lines were temporary, but had forced the 3,400-Megawatt Suralaya coal-fired power plant in West Java to shut down.

Muljo said it took several hours to get the power plant back onstream once it had been shut down. This, he said, was what kept several areas in the dark for several hours.

PLN general manager of power distribution in Jakarta and Tangerang, Margo Santoso, said the blackouts had nothing to do with too much power demand overburdening the transmission lines.

"If that were the case, we would have asked large industrial customers to unhook themselves from our system and use their own power supplies to prevent the blackouts," he said.

Recent talk of a power crisis has concerned consumers, with PLN frequently warning that it may not be able to meet the nation's growing thirst for electricity.

Indonesia lacks new investment to cope with a surge in power demand. PLN and experts have warned that without additional power plants and transmission lines, the country may have to cope with more blackouts as soon as two years from now.