The fire that broke out on the 26th at the National Information Resources Service (NIRS) in Yuseong District, Daejeon, is believed to have occurred when sparks flew during work to physically disconnect the uninterruptible power supply (UPS) batteries in the data center.
Lee Sang-min, director of operations planning at the NIRS, said at a briefing on the 27th, "It was dangerous to have the UPS batteries in the data center alongside the servers, so we were in the process of moving them underground," adding, "We were disconnecting the cables from the batteries and cutting the power, and it appears that after the power was cut, sparks occurred under some circumstance and a fire broke out." He added, "The exact cause will be determined through forensics."
Industry sources are suggesting the possibility that a short circuit occurred while dismantling cables without completely cutting off UPS power. As a rule, power to the UPS must be cut before working during relocation work, but if wires are disconnected while power remains, voltage can spike momentarily and a spark can occur.
An industry official said, "A UPS uses direct current rather than household alternating current, and if a wire is suddenly disconnected under direct current, there is a risk that the voltage will spike sharply and insulation will fail," adding, "It is possible that this electrical characteristic contributed to the fire."
Meanwhile, the UPS system at the center of the fire was a product manufactured and supplied by a client company that received battery cells from LG Energy Solution around 2012–2013, and it reportedly passed a regular safety inspection conducted in June this year.
The fire broke out in the NIRS data center on the afternoon of the 26th and was initially brought under control after about 9 hours and 50 minutes. Fire authorities said that after completely removing residual heat and smoke on the morning of the 27th, they plan to proceed with moving the lithium-ion batteries outside.
According to fire authorities, the fire started in a battery pack installed in a corner of the data center and spread to adjacent areas. The data center is divided into two spaces, with 192 lithium-ion battery packs installed on each side for a total of 384. Initially, it appeared that only one side was damaged, but due to the structure connected by cables, the flames are believed to have spread to the opposite side and destroyed the whole area.
Kim Gi-seon, Director General of the emergency response control headquarters in Yuseong District, Daejeon, said, "As the internal temperature of the data center remained high for a long time, most of the server equipment also appears to have been damaged." Kim said, "There was a halogen fire suppression system in the data center, and while halogen can help prevent initial spread, it is less suitable for lithium-ion battery fires," adding, "At present, essentially the only means of extinguishing is to pour large amounts of water to cool it."
Fire authorities are currently venting heat and smoke to the outside and taking follow-up measures by immersing the remaining battery packs in water and moving them outside. Even if the flames are fully contained, there is a possibility of re-ignition as internal heat rises again, so they are focusing all efforts on removing residual heat.