It is a pipe attached with the conservator as shown in Fig. 18.4. With the expansion of the oil, when it is heated, the hot air comes out from the conservator through this pipe. The movement it is cooled, the air is being sucked in via the same pipe, this action is known as the breathing action of the transformer. Now the moisture is the main factor which effects the dielectric strength of the transformer oil. So a provision to absorb the moisture from the air to be breathed in is provided just on the mouth of the breathing pipe as shown in Fig. 18.4. The CaC12 or silica gel is kept there to absorb the moisture and the clean and moistureless air is allowed to come in, thus this air will not effect adversely on the dielectric strength of the transformer oil.
The color of the silica gel or CaC12 becomes blue while it absorbs moisture in sufficient quantity, now it should be replaced. A filter is also provided with the breather which prevents the dust etc. entering the transformer tank.
Conservator. It is a small tank mounted over the top of the main tank as shown in Fig. 18.4. It is sometimes called as the expansion tank. A level indicator is fitted to check the level and colour of the transformer oil. The main tank is completely filled with the transformer oil and the Conservator partially. With the increase and decrease Of current (load) the heat produced is also increased and decreased; as a result the expansion and contraction of the oil takes place; so the conservator is not filled completely to facilitate the expansion etc. An instrument is also attached to indicate the temperature of the oil.
