Telstra today released a report into the circumstances surrounding the fire at its Warrnambool exchange in regional Victoria, which cut off more than 65,000 services for a number of weeks in November 2012 and has been estimated to have directly cost the area AU$17.9 million.
The report (PDF), compiled by Telstra's director of fixed and data access engineering David Piltz, indicated that the fire started at 4.35am AEDST on November 22, 2012, in the maintenance control room of the exchange as a result of an electrical fault in that room or in the ceiling above the room. Piltz couldn't pinpoint the cause to a single source or the specific defect that caused the spark, but he said the melting of the cables onto the desks, floor, and ceiling in the room most likely caused the fire to start.
The fire was able to be spread around the exchange as air-conditioning systems were left pumping air through the facility, thanks to power provided through a backup generator.
Telstra employees had left the smoke doors of the maintenance control room open, which also helped spread the fire.
"The fire damage was quite extensive, not only from the heat and smoke, but also from the chemical residues from burnt plastic cables that were distributed throughout the electronic equipment, particularly in the exchange building's south and western sides," he said.
"In my opinion, this was due to the air-conditioning systems continuing to operate until at least 5.08am, when the standby generator was shut down."
The fire completely destroyed cables connecting telephone and broadband equipment to the main distribution frame in the exchange, which cut off 100,000 residents in the area from the rest of Telstra's network. The rest of the exchange was damaged by smoke, soot, and heat from the fire.
Piltz made 22 recommendations in the report, and has suggested that when exchanges are inspected in regional Australia, there should be thermal imaging of cabling in ceilings to detect overheating or faults in electrical wires, and for staff to be trained on the requirement to close smoke and fire doors.
As a result of the fire, 61,856 PSTN phone lines, 14,409 ADSL services, 56 ISDN services, 40 3G mobile base stations, 138 IP metropolitan area network services, and 13 Telstra direct services were cut off.
Warrnambool is a switching node and a transmission hub for Telstra, and the fire had flow-on effects to 135 other exchange areas across south-western Victoria, and 85 schools, 20 hospitals, 27 police stations, 92 fire stations, and 14 state emergency service units all had services either cut off or reduced by the fire.
Telstra brought in 110 technicians working rotating 12-hour shifts to get all services back up by December 19, 2012. Piltz said that Telstra's recovery method had been very effective, managing to restore services in 20 days in what would have normally taken months.
A complete repair of the exchange began in February 2013, and is scheduled for completion by the end of June 2013.