Oil-immersed transformers use oil as the main insulation means of transformers, relying on oil as cooling medium (self cooling, air cooling, water cooling). The main reason for putting pebbles in the oil pit of oil-immersed transformer is to prevent fire and drain oil.
The part under the oil-immersed transformer is usually called unloading pool or unloading oil, leading to the accident oil pit or accident oil pool. In the event of an accident, such as oil injection or explosion, the transformer oil will flow into the unloading pit by pebbles, and then flow to the accident oil pool, then the pebbles under the transformer play an isolation role, reduce the fire, conducive to fire suppression; In addition, the high temperature transformer oil can reduce the fire after cooling by pebbles.
Some do grid in the pool, and some do not do grid. For those who make bars, pebbles are placed on the bars; Do not do fence, pebbles placed in the discharge pit. Placing cobblestones to facilitate oil unloading is one reason, in addition, insulation, easy maintenance, operator inspection, work is another reason.
Prevent the transformer fire oil leakage to the ground is still burning, also will not block the oil drain hole at the bottom of the drain pit. Oil in the transformer cobblestone gap flow to the following, the surface to avoid oil, oil drainage it also plays a role in cooling oil temperature, to prevent oil combustion.
