Oil immersed transformer is used as the insulation medium (oil immersed transformer is mainly used as the cooling medium). The main reasons for putting pebbles in the oil pit of oil immersed transformer are fire prevention and oil drainage.

The lower part of oil immersed transformer is usually called oil unloading pool or oil unloading, which leads to accident oil pit or accident oil pool. In case of an accident, such as oil injection or explosion, the oil of the transformer will flow into the oil unloading pit through the pebbles, and then flow to the accident oil pool. At this time, the pebbles under the transformer play an isolation role to reduce the fire and help extinguish the fire; In addition, the high-temperature transformer oil can reduce the fire after being cooled by pebbles.

In the pool, some are made of grating, and some are not made of grating. The cobblestones are placed on the fence; If there is no barrier, the pebbles are placed in the oil unloading pit. Placing pebbles for easy oil unloading is one reason. In addition, insulation is also one reason for easy maintenance and inspection by operators.

Prevent the transformer from burning when the oil is discharged to the ground when it is on fire, and will not block the oil drain hole at the bottom of the oil drain pit. The oil flows down between the pebbles of the transformer to avoid oil contamination on the surface. When the oil is discharged, it also plays the role of cooling the oil temperature to prevent oil combustion.