Endesa has installed a dry-type transformer with a power of 31,500 kVa and 72.5 KV voltage in the Arjona substation in Seville; this is the largest transformer of its kind to be installed anywhere in the world. The dry-type transformer, manufactured by ABB in their Zaragoza plant, significantly increases the quality of the electricity supply, reducing the risks inherent to conventional oil technologies such as fire and environmental pollution risks, as the oil used to cool conventional transformers is replaced by a resin that does not melt at the expected high working temperatures.
The transformer uses an epoxy resin as an insulating system, mixed with small particles of quartz sand (glass fibre) which, in the event of a fire, absorb the heat and reduce the combustion temperature. This dry technology means the almost 18,000 litres of mineral oil that are used to cool similar size conventional transformers do not have to be used. Instead an encapsulated technology is used which makes them self-extinguishable if there is a fire in the installation.
The transformer installed by Endesa serves over 5,000 customers and has a power that is ten times that of the dry-type transformers used until now worldwide. The suitability of this type of technology for use in urban centres and closed premises explains why the substation in Seville was chosen to introduce the new model of dry-type transformers, with three more units being installed in the near future by Endesa. In fact, the company plans to install a new dry-type transformer in the Substation of Osario (Seville) after the summer.
This dry-type technology simplifies maintenance and significantly reduces the risk of environmental pollution as it eliminates the risk of mineral oil leakages. Dry-type transformers can also function at 165 degrees centigrade, compared with the 100ºC of conventional models and their design enables the average life of conventional transformers to be increased by between 20 and 40 years.