(1) When the volume of transformer oil expands or contracts with changes in oil temperature, the conservator (oil tank) serves to store or replenish oil, ensuring that the main tank is always filled. This also reduces the contact area between the oil and air, thereby slowing down oil deterioration. On its side, there is an oil gauge (ferromagnetic oil level indicator) to monitor oil level changes. The size of the conservator is determined by the standard that it is visible when the transformer is out of service in winter and does not overflow in summer, roughly about 1/10 of the transformer's oil volume. For the ferromagnetic oil level indicator, the reading should correspond to the temperature-oil level curve on the transformer body.
(2) Transformer conservators are divided into those for the main body (main tank) and those for the tap changer. The main tank oil level is required to be slightly higher than the tap changer oil level to prevent oil from the tap changer tank from seeping into the main tank and affecting the insulation of the main tank oil. Since the oil in the tap changer tank also serves to quench the arc, it deteriorates faster and contains more impurities. The purpose of the tap changer oil filtration unit is to automatically filter the oil after each tap-changing operation under load.
