What fire prevention measures are available for power transformer failures?

Failures in power transformers are commonly caused by severe overload operation, short circuits due to winding insulation degradation, aging of transformer oil, excessive contact resistance at connections or tap changers, failure of high- or low-voltage fuses to operate during external short circuits, core damage, internal arcing in oil, and lightning strikes.

Since transformers are filled with insulating oil, fires can have severe consequences—ranging from oil spraying and ignition to, in extreme cases, rapid gas generation from oil decomposition, leading to a sharp pressure rise inside the tank, tank rupture, massive oil leakage, and intense combustion.

Preventive measures include:

(1) Equip transformers with fuses or relay protection devices. For larger-capacity units, gas (Buchholz) relays should also be installed to promptly isolate faulty transformers from the grid.

(2) Strengthen insulation monitoring through regular preventive insulation tests and scheduled maintenance or rotation overhauls.

(3) Properly manage insulating oil: if oil aging, moisture ingress, or reduced dielectric strength is detected, filter or replace it with qualified new oil.

(4) Install transformers either outdoors or inside buildings with Class I or II fire-resistance ratings, ensuring adequate ventilation.

(5) Enhance operational management by monitoring transformer loading during peak periods. If overload is detected, redistribute loads or replace the unit with a higher-capacity transformer.

(6) Regularly inspect lightning arresters for proper operation and promptly replace any defective units.

(7) Promote the use of fully sealed power transformers. For high-rise buildings and other critically important locations, select flame-retardant or self-extinguishing dry-type transformers or prefabricated (pad-mounted) units.