Transco information officer Benjamin Ypil said the bolt of lightning affected lines 1 and 2 of the Compostela-Banilad transmission line which feeds power from the Tongonan geothermal plant in Leyte to the Cebu-Negros-Panay grid.
With the power feed from Leyte abruptly disrupted, brownouts descended on many parts of Cebu, Negros and Panay, some lasting as long as two hours.
Ypil said it could not yet be determined exactly where on the Compostela-Banilad line that the lightning struck. which came in the middle of a thunderstorm.
The Transco official said only Leyte, Samar and Bohol in the entire Visayas grid were spared from the power supply disruption.
Of the three affected islands of Cebu, Negros and Panay, power was restored quickest in the latter, aided in large part by the presence of two power barges there. Power to Panay came back in just 38 minutes.
As for Cebu and Negros, power was not restored until shortly after 1 p.m., Ypil said.
Ypil also said that many parts of Negros were not affected at all by the blackout because the island has its own power supply from the Palinpinon geothermal plant.
The two generating plants in Palinpinon continued to churn out a combined 160 MWs of power during the brief crisis.
At the time of the incident, Leyte was supplying the Cebu-Negros-Panay grid with 200 MWs of power, Ypil said.
The lightining eliminated 600 MWs from the 720 MWs in the Cebu-Negros-Panay grid.
Ypil said the damage caused by the lightning to the Transco transmission lines was expected to be minimal.
In Metro Cebu, the affected area was so wide that only those served by the Veco substation in consolacion were spared. The Veco substation in Consolacion serves both that town and nearby Liloan.
Veco holds the biggest power distribution franchise for Metro Cebu.
Ethel Natera of Veco said all the other areas served by other substations lost power. This meant that from Mandaue City to San Fernando, the power was out.
No immediate reports of business losses due to the blackout were made available as of press time.
Many businesses, however, have their own generating units that immediately swung into action.
Operations at the Capitol, City Hall and other government offices went on with only slight inconveniences.