Most power transformers can have their rating improved on-site with minimal disruption to the network. Upgrading transformers have three key advantages:

  • A higher MVA rating saves the costs associated with buying new transformers.
  • It also saves the disruption to the network & the site associated with replacing plant.
  • With a lower operating temperature the expected life of the transformer is increased.

     Before recommendations are made, a thermal assessment of the existing cooling arrangement is carried out. New designs are prepared and the necessary equipment specified and procured. We complete the uprating with Site installation and commissioning. A re-design of the cooling can require, new cooling radiators, heat exchangers, oil circulating pump or just cooling fans as necessary.


      All designs are supported by detailed thermal calculations giving top oil rise, average winding rise and hottest spot temperature at the enhanced rating.

Distribution and power transformers are designed, manufactured and tested to withstand higher loads than their nominal design rating as required by industry standards based on the dissipation of losses in the form of excess heat from the transformers core and windings. By increasing the efficiency of heat dissipation and controlling this without exceeding the specified temperature rises, a transformer is able to operate safely at an increased rating without reducing its lifecycle. Following a thermal analysis and design study between the existing and desired rating, the cooling system of a naturally cooled transformer (ONAN) could have additional radiators or new cooler bank installed; cooling fans or heat exchangers could be added to increase dissipation (ONAF) or another option may be the installation of oil circulating pumps within the existing cooling system (OFAF). Uprating a transformer by any of these methods is significantly more cost effective than the purchase of a new transformer.


      Another advantage is the minimal disruption to a clients’ high voltage network as the majority of the work is design calculations and preliminary fabrication, meaning that installation and testing can be completed during a maintenance outage rather than a major works outage.


     If the cooling system of a distribution or power transformers has already been uprated to its maximum potential, we may be able to offer a transformer rewind package to achieve further load potential.



You can contact our administrative office to arrange a meeting or site visit by one of our specialist project engineers for the above need.