Guam -2 line faults along Ypao Road in Tamuning triggered a series of events Wednesday night that led to an islandwide power outage.
A number of residents reported seeing a 2 bright flashes of light along Yapao Road in Tamuning.
The first coming from a power pole on Ypao Road next to the SDA clinic just after 7 pm. And then a much larger and brighter flash about 7:15 pm that came from a power pole across the street from the Days Inn.
Guam Power Authority Spokesman Art Perez explained that the first line fault was detected by the 2 base load Cabras Units, 3 and 4, and that prompted them to shut down taking 15 of the island’s more than 40 circuits off line.
At that point, Perez says that protection relays at the Tamuning Substation should have kicked in to isolate the outage. But they did not.
“What didn’t happen, it failed to isolate,” said Perez on the K-57 Breakfast Show this morning, “and some of the protection relays did not work.”
About 7:15 pm, the second line fault along Ypao Road occurred, and because the protection relays didn’t work, the Tanguisson Power Plant detected the second line fault and took itself off line and an islandwide power outage ws the result.
Perez said the second line fault occured at a time when the system was already under stress from the first fault.
GPA’s “defenses were pretty vulnerable at that time … taking off that much load at one time.” In addition, the 2 line faults occurred at a time when the system was under peak demand with so many residents home, cooking dinner, watching TV.
Power was eventually restored to Tumon, Barrigada, Dededo and Hagatna just before 9 am. Full power was restored by 2:30 am this morning.
The cause of the protection circuit failure remains under investigation, as well as what caused the initial fault.
However, GPA officials on the scene along Ypao Road this morning found a dead brown tree snake next to the power pole near the SDA Clinic which might have been triggered the first line fault, leading to the second line fault and triggering the blackout. But no final determination has been made.