Transformer Oil level in conservator tank or how much oil in the conservator tank is not a matter; the real matter is that the tank should not be empty anyway. There should be some oil in the conservator tank for safe operation.
As the transformer oil has a high expansion and compression value with temperature, with high temperature the oil volume increases and low temperature the oil volume decreases significantly.
The design consideration for power transformer is to cope up the oil level increment with temperature. As per IEC the conservator design should be considering oil level increment with temperature ranging from -25°C to plus 110°C.
The oil level of a transformer conservator tank is not fixed or constant; instead it is a function of the following parameters-
· Oil temperature of the transformer (average value).
· Ambient temperature.
· Solar radiation.
· Transformer loading.
Oil level in transformer conservator tank is not a fact. Presence of oil in the tank is good enough. The real challenge is to maintain a neutral oil level to avoid over flow or being empty with the temperature change.
It is a better practice to fill up and maintain the oil level to the oil level at average temperature value
So practical considerations for filling up the conservator tank with oil is to achieve the following things at the same time-
· Avoid empty conservator in low load, cold environment.
· Avoid over flow or spillage of oil in full load or hotter environment