Transmission-related power outages decline last year

The number of transmission-related power interruptions and outages dropped in 2007, data from the National Transmission Corp. (TransCo) indicated.

TransCo said it registered a sustained average interruption frequency index (SAIFI) of 0.63 in 2007, a 3.08-percent improvement from the 2006 level of 0.65. A lower SAIFI means lesser number of times that a customer is out of power due to TransCo-caused outages.

Aside from SAIFI, another service quality indicator include internationally recognized index such as sustained average interruption duration index (SAIDI), the length equivalent of time in hours of power interruptions that a customer experiences in a year.

Less frequent and shorter power fluctuations or interruptions that hamper power customers’ activities translate to more reliable electricity service.

Other indicators that gauge the reliability of power delivery to TransCo customers include unserved energy (UE), or the amount of energy a customer was not able to use due to power interruptions, and system availability (SA), or the time that major components of the transmission system such as lines, breakers and transformers are available.

For the SA level, TransCo registered 99.63 percent system availability in 2007, 11 percent higher than the 99.52-percent availability in 2006.

In terms of TransCo’s ability to restore transmission service after a power interruption within a short time period, SAIDI went up slightly from 0.66 hours in 2006 to 0.75 hours in 2007.

Undelivered or unserved energy due to power interruptions also sustained a 17.81 percent increase from 8.03 gigawatthours (gwh) in 2006 to 9.46 gwh in 2007 (one gigawatthour is equal to one million kilowatthours).

TransCo attributed the increases in SAIDI and UE levels to sustained outages and insulator troubles.

Sustained outages or interruptions were traced to corrective maintenance procedures on faulty breakers as well as cross-arms of transmission poles. Technical difficulties due to inclement weather were also recorded.

To improve power quality and reliability within the grid this year, TransCo said it would continue to enhance maintenance and operating policies and practices in all its installations nationwide and install parallel routes as well as isolators or disconnecting switches to sectionalize long power lines in case of power interruptions.

TransCo is also fast-tracking transmission line upgrading and substation expansion projects as indicated in the Transmission Development Plan to ensure the efficient delivery of electricity to power customers.

 The transmission firm noted that the permanent restoration of transmission facilities damaged by typhoons in 2006 is almost complete, with the full restoration expected by May 2008.