A blaze at Moorabool’s Victorian Big Battery most likely resulted from a cooling system leak that caused a short circuit, an investigation has found.
Energy Safe Victoria (ESV) released the findings on Tuesday morning after a two-month investigation into the fire on July 30.
The independent energy safety regulator conducted extensive investigations at the site while analysing data from site owner Neoen and its contractors UGL and Tesla, which operate the site.
ESV found the cooling system leak and short circuit in a 13-tonne lithium Megapack resulted in overheating, leading to a fire in a nearby battery compartment damaging two Megapacks.
The regulator also noted further contributory factors, such as the Megapack being switched into an off-line service mode, resulting in its protection and monitoring systems being inactive.
These included a high voltage controller that could have operated a pyrotechnic fuse to disconnect the faulty battery unit.
The Megapack that caught fire had been in service for 13 hours before being switched into an off-line mode when no longer required as part of the commissioning process.
A 24-hour delay in connecting the batteries to the supervisory control and data acquisition (SCADA) system also meant no active monitoring of the Megapack alarms.
ESV has required the site’s owners and operators to implement additional safety measures including:
• full pressure testing of Megapack cooling systems when installing onsite,
• inspecting cooling systems for leaks after testing,
• shorter connection times to the SCADA system to help alert Tesla with specific alarms,
• a new battery module isolation loss alarm, and
• procedure changes for Megapack protection systems.
ESV stated work could recommence onsite on Wednesday as the owner and operators had implemented these changes.
ESV will continue its investigation to determine if any breaches of the Electricity Safety Act occurred.
“Safety is crucial in the delivery of the 300-megawatt battery storage project, which will store reserve power for Victoria,” ESV commissioner Marnie Williams said.
ESV has ordered Tesla to provide the final results of its investigation, when available, into how the fire spread to a second Megapack.
Timeline of events
Friday July 30
10.15am – Site supervisors noticed visible smoke emitting from one Megapack. They electrically isolated the site and called emergency services.
10.30am – Emergency services arrived, set up a 25-metre exclusion zone and started spraying water on equipment surrounding the Megapacks.
4pm – Visible flames subside.
Saturday July 30
Fire authorities monitored the continued temperature decline of Megapacks using drone technology.
Sunday August 1
1pm – CFA stopped applying the precautionary water and approached Megapacks to monitor surface temperatures.
Monday August 2
3.05pm – Megapack doors removed for temperature check and site declared under control.
