8 things you should know about transformer vacuum filling,standing and hot oil circulation
Regarding transformers with voltage levels of 60KV and above, transformer vacuum filling, standing and hot oil circulation should be carried out when the transformer body is exposed to moisture, overhaul, and new installations.
Transformer Vacuum Filling
1.Control value of vacuum degree during vacuum oil filling:
| Transformer voltage level | Vacuum degree |
| 66-110kV | 0.02 Mpa-0.05Mpa-0.08Mpa |
| 220 kV | 133Pa -0.1 MPa |
2.In the initial stage of vacuum pumping (Transformer Evacuation), the degree of vacuum should increase uniformly to facilitate the mechanical strength requirements of the oil tank’s vacuum. The 66-110kV transformer can reach the above-mentioned vacuum requirements within at least one hour.
3.When the transformer body considered have traces of moisture due to long exposure time or other reasons, it is necessary to maintain a long-term vacuum after evacuation. The persistence time may determine by the degree of moisture. Generally, it can take 8-24 hours to facilitate the evaporation of water.
4.When do the transformer vacuum filling work, please make sure that the air in the pipeline drained, open the filling valve and fill the oil. The oil injection should be from bottom to top, and the oil injection speed should be 2-3,000l/h, not more than 6,000l/h, to prevent the oil flow from being electrified. When the oil level is 100-200mm from the top of the tank, stop the oil injection and continue to maintain the vacuum degree. The 110kV transformer must maintain the vacuum for not less than 2 hours, and the 220kV transformer should be not less than 4 hours.
5.The requirements of the primary accessories of the transformer during vacuum filling: the oil conservator, oil purifier, cooler (radiator, cooler) and other accessories that cannot accept the mechanical strength of the vacuum should be closed to the butterfly valve to block the oil tank; The on-load switch should connect its oil chamber with the transformer oil tank to vacuum together.
6.A Vacuum Oil Purifier Machine should be used for transformers above 66kV, and plate-type oil filter unit should not be used to prevent the oil from being degraded, bringing in air and moisture.
7.The oil temperature during oil filling should be higher than the temperature of the transformer’s body. The lowest temperature of the body should be above 10-20℃, or when the ambient temperature is low, the oil temperature should be increased to 30-50℃ before filling.
8.For the oil filling in the tank of the on-load tap changer switch, make sure to fill the oil under vacuum, and fill the oil together when filling the oil tank.
Analysis on the operation of hot oil circulation after transformer vacuum filling
1.The transformer should be vacuum filled with oil up to 100-200mm from the top cover. When the hot oil is circulated, the vacuum degree should be maintained meet the specified requirements.
2.Connect the oil circulation pipeline while the transformer is kept in a vacuum state. The oil filtration machine’s oil inlet pipeline is connected to the bottom valve of the transformer, and the oil filtration machine’s oil outlet pipeline is connected to the oil filling valve on the top of the transformer.
3.Open the vacuum pump and the inlet valve of the oil filtration plant, After evacuating the oil inlet pipe, open the valve at the bottom of the transformer to allow the oil filtration unit to enter the oil and perform hot-circulation to heat the oil. Open the oil filling valve on the top of the transformer, so that the air in the oil filling pipe is discharged through the vacuum pump. Open the oil outlet valve of the oil filtration unit to do the hot oil circulation.
4.When the hot oil is circulated in the full oil state after the transformer vacuum filling with oil to the specified oil level of the oil conservator, the transformer will not be vacuumed. The treatment of the oil inlet pipeline of the oil filter is the same as above. When the oil outlet pipeline of the oil filter is connected, the oil filling valve on the top of the transformer is equipped with a bleed plug. The bleed plug is used to discharge the gas in the pipeline, when the oil pipeline is filled with oil, the valve on the top of the body is opened for heating by circulating hot oil. .
5.Before circulating hot oil under full oil condition, check that the moisture absorber has been installed correctly and is working normally.
6.When the hot oil is circulating, the oil temperature at the outlet pipe should not be lower than 50°C, and the temperature in the oil tank should not be lower than 40°C.
7.For maintaining vacuum degree of the transformer during hot oil circulation, the oil replenishment sequence is the same as that of vacuuming and oil replenishing.
8.The oil sampling inspection after the hot oil cycle shall meet the requirements of the current national standard “Electrical Installation Engineering Electrical Equipment Handover Test Standard”.
9.After the hot oil circulation of the transformer is completed and the transformer vacuum filling is completed, it should be allowed to stand for a period of time before applying voltage. The standing time should not be less than the following regulations:
10.After the transformer has been stand for rest, deflate several times from the relevant parts of the transformer bushing, riser, cooling device, gas relay and pressure release device, and start the submersible pump until the residual gas is exhausted.
I-10℃ Transformer Oil (Naphthenic) I-20℃ Transformer Oil (Naphthenic)
I-30℃ Transformer Oil (Naphthenic Alkyl) I-40℃ Transformer Oil (Naphthenic Alkyl)
High overload transformer oil HID50# transformer oil (ultra high voltage DC transformer)
Want a transformer vacuum filling plant’s price, please INQUIRY NOW
