For transformers and substations, an overheating can lead to an ignition of the insulating oils. Although insulating oils have a high ignition temperature, if this is exceeded, an explosive outbreak of fire may ensue.

A heat detector cable can be used for the detection of the fire. A water spray extinguishing system is most commonly used as the extinguishing system. The simultaneous and equal distribution of water quickly extinguishes the fire and prevents a further breakout. The relatively small water droplets ensure a quick cooling down of the overheated parts and the prevention of a reignition. This quick extinguishing of the fire means that there are no long-term operational failures. After a short inspection, the systems are ready for further use.