Transformer tank pressure test during the manufacturing
Transformer tank pressure test during the manufacturing
(OP)
Is there any thumb rule to quickly estimate what should be the rated static pressure of the tank of a 132/34.5kV, 140MVA transformer, with the conservator at a height of 2.5 meter.
IEC 60076-1 states that the tank shall be tested for the pressure of at least 30 kPa over the normal liquid pressure.
By applying the above standard, the static pressure in this case is expected to be about 2.5 mtr x 0.8 = 2 bar, assuming the specific gravity of oil is 0.8. Hence the test pressure shall be
= 2 bar + 30 kPa
= 2 bar + 0.3 bar
= 2.3 bar
I would appreciate if someone from the fraternity could validate or comment on the above.
IEC 60076-1 states that the tank shall be tested for the pressure of at least 30 kPa over the normal liquid pressure.
By applying the above standard, the static pressure in this case is expected to be about 2.5 mtr x 0.8 = 2 bar, assuming the specific gravity of oil is 0.8. Hence the test pressure shall be
= 2 bar + 30 kPa
= 2 bar + 0.3 bar
= 2.3 bar
I would appreciate if someone from the fraternity could validate or comment on the above.






RE: Transformer tank pressure test during the manufacturing
The leak test in a transformer is done at various stages. As per IEC 60076-1 ed3.0-2011, it shall be with 30kPa over the normal oil head in transformer for 24 hours for trfs >20 MVA or >72.5 kV. For lower ratings pressure test is for 8 hours (clause 11.8)
When tank is fabricated, it is done with water filling and equivalent pressure generated at tank bottom.
At factory and at site (if demanded by user) it is done by applying dry air pressure inside the air bag or over the oil level in conservator. Another way is to pressurize oil inside the tank after closing valve to conservator using oil filter machine so as to get equivalent pressure at tank bottom. This will avoid air dissolving in to oil.
RE: Transformer tank pressure test during the manufacturing
RE: Transformer tank pressure test during the manufacturing
IEC has other tests also for the points raised by scotty.
Clause 11.9- Vacuum deflection test
Clause 11.10 -Pressure deflection test
Clause 11.11- Vacuum tightness test at site
RE: Transformer tank pressure test during the manufacturing