Electrical Contracting News (ECN) May 2016 - Page 35

POWER DISTRIBUTION TRANSFORMING THE MARKET A transformer is expected to last the life of a building. Transformers are perhaps one of the single most important aspects of a building’s services, acting as the key connection between the national grid and the premises’ internal power distribution network. For years, oil transformers have been the go-to choice for consultants and specifiers, yet advances in rival technologies are now putting credentials of the age-old favourite under the microscope. Here Steve Marr at Legrand UK delves deeper into the debate. L ike so many other aspects of the electrical industry, the transformer debate is one full of nuances and historical bias. Oil transformers have long been the transformer of choice for many specifiers and consultants. The technology has been in use for over 100 years and has formed a reliable power conduit for industrial and commercial projects across the world for decades. However, the rise in alternative transformer technologies, typified by the development of cast-resin transformers (CRTs) in the 1980s, sparked a debate into whether the days of the oil transformer are numbered. Turning point Over 25 years on and the debate is still going, however the tide may be turning in favour of CRTs, with consultants and specifiers firmly focused on sustainability going forward with new projects. A transformer is expected to last the life of a building, and with most buildings generally lasting 20 years before they are refitted or repurposed, it would be very unusual for a transformer to be replaced during this time, bar a serious technical issue. However, it is the sustainability factor – taking into account a transformer’s emissions and its overall total life cost – which may give CRTs the edge of their older counterparts. Despite their reliability over the years, oil transformers do present a number of issues – both during the installation stage and their subsequent operational life – which CRTs do not, all of which should certainly be factored in during the specification process for new transformers. In oil transformers, the windings are inserted inside an enclosure filled with a liquid – generally mineral oil, which has the double function of guaranteeing adequate insulation between the windings and the earth, and dispersing the heat generated by the normal operation of the transformer itself. The oil increases in volume as the temperature of the surroundings of the transformer itself rises. To compensate for these variations of volume within the insulating liquid, some transformers have an ‘expansion vessel’, situated in the upper part. This tank communicates with the outside by means of filters to remove the humidity which, if it accumulated, could impair the dielectric properties of the oil, and consequently the transformer itself. 35 35-36 Power Distribution – Legrand.indd 35 11/04/2016 14:23