Power transformer tanks - a weak link

Often the damage we see in power transformers involves the tank itself. So in this post I'll describe the power transformer tank, and give some tips on maintaining it.

The transformer tank provides the containment for the core and windings and the dielectric oil. The tank acts as the vacuum vessel for impregnating the transformer with oil.

The tank has a removable cover so that core and windings can be accessed and removed. The cover is fastened by a flange around the tank and is bolted. It should be inclined at about one degree to help drain rainwater.

The cover holes are made oil tight using gaskets. These are normally rubber bonded cork or neoprene bonded cork or stiff rubber. The rubber is synthetic rubber, so to resist degradation by the mineral oil. These gaskets joints represent a potential leak, and often is the source of more serious problems that occur due to poor maintanance.

The main tank cover flange usually represents the greatest oil leakage threat, since being of large cross section, it tends to provides a path for leakage flux, with the resultant eddy-current heating leading to overheating and degradation of gaskets.

From our experience, oil leaks are the first visible signs of deeper trouble. Therefore, we highly recommend to visually inspect power transformers on a regular basis. These checks must be done by qualified personnel, as the voltages from power transformers are deadly. checks for leaks around the cover flange, insulator gaskets and other auxiliary equipment are done as part of a routine maintenance check. It is fairly important, as an early diagnosis can save A LOT of money resulting from damage to the transformer later on (due to overheating) and the equipment connected to it (due to shorting) or around it (due to exploding).

Megawatt Transformers provides transformer maintenance that includes thorough testing of the transformer tank's gaskets, transformer oil analysis and transformer repairs. Contact us for more details.