Oil filled versus cast resin

Atransformer is a device that transfers electrical energy from one circuit to another through a shared magnetic field. A key application is to tap off 11,000 volts (11 kV) of electrical power from the national grid and step it down to 415 volts, which is the normal 3-phase electrical power system used in the UK for commercial, institutional or industrial applications. A transformer therefore makes raw electricity usable, as well as allowing it to travel through cables. In fact, most of the world’s electrical power has passed through transformers by the time it reaches the consumer.
Large, high-power transformers, in particular, need to have a built-in cooling facility to transport heat from the interior. Thus, one of the numerous ways of classifying transformers is according to cooling type. For example, for power transformers rated up to a nominal kVA, natural convective air-cooling, often fan-assisted, is adequate. Traditionally, oil transformers relied on highly refined mineral oil as a cooling medium, while with the latest generation castresin transformers the transformer core is insulated by a thin coating of inorganic material.
Fire safety
Over the last decade the remarkable advances in materials technology and manufacturing methods have fostered the popularity of cast resin transformers, particularly in fire-sensitive locations such as high-rise structures, hospitals, and public buildings where the transformer is located indoors and a fire outbreak would be particularly hazardous because of the high density of people.
Safety is high on the list of benefits provided by cast resin transformers manufactured by Zucchini. The advanced epoxy mixture used in EdM transformers is a nonhazardous material, which is both fire-resistant and selfextinguishing. Even when the material is exposed to arcing, no toxic gases are produced, and the transformer can be safely situated close to the load, saving on cabling, civil works and transmission loss.
Another key benefit is the fact that cast resin transformers require no maintenance during their lifetime.
Compare all of these benefits with the disadvantages of traditional oil transformers with their relatively low fire point, pollution potential, higher installation costs (due in part to the fire-protection and containment measures often needing to be installed along with the installation), and a high maintenance requirement. Oil-cooled transformers are not, it has to be said, a favourite with insurance companies.
Oil, of course, is a nonrenewable resource, while EdM transformers are insulated in a sustainable material, which has been developed and refined over 15-years to comply fully with European Union and national directives on the protection of the environment. Indeed, they do not pollute the environment where they are installed and are therefore recommended for all ISO locations, a standard that helps organisations minimise the negative effects of their operations on the environment.
Aggressive conditions
As well as protecting the environment, the high quality epoxy resin filled with silica and trihydrate alumina, that have been developed to encapsulate transformers, stops moisture ingress, thus preventing electrical breakdown under load, as well as inward pollution from the environment. This not only makes the transformers ideal for damp or dirty conditions, but extends the life of the transformer’s working parts and eliminates maintenance. EdM transformers are also coated in high-vacuum chambers to reduce air and other gases in the resin that could produce partial earth discharges. In effect, they thermetically seal the transformer’s core. As a result, consultants and specifiers looking for standard transformers with power outputs in the range of 100 to 3,500 kVA (and up to 16,000 kVA for specific projects), get complete peace of mind.
Another point to make is that cast resin transformers do not have the noise and vibration problems associated with oilbased machines.
Cast resin transformers are now available in different specifications to meet the needs of the climate or hazardous and unforgiving environments, exceptionally cold ambient temperatures and environments with high fire risk.
Number one cost-savers
One of the most gratifying outcomes of installing environmentally friendly technology in recent years has been the realisation by individuals and companies that saving the environment can also save money. As well as being favourably priced, cast resin transformers are exceptionally energy-efficient, producing a high transformation yield and thus consuming less input energy.
At Zucchini EdM, we have developed mathematical models highlighting the savings that can be made by the user of a given electrical item on a case-bycase basis. For example, a 1,000 kVA energy-efficient transformer produces savings of €30,000 over a 20-year period, the equivalent of 20 MWh per year.
The European Commission has assessed that if equipment such as this were brought into general use, emissions of 11 million tonnes of carbon dioxide – equivalent to the electrical power used by 5 million homes – would be avoided.
Cast resin transformers provide:

  • More energy output for less input
  • Environmentally friendly technology
  • Easier installation
  • Exceptional reliability
  • Increased safety
  • Non polluting
  • Minimal noise and vibration
  • No maintenance costs
  • No civil works costs
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