Power transformer maintenance. Field testing.（电力变压器的维护。）.pdf

Power transformer maintenance. Field Testing. Andrés Tabernero García Hardware Project Manager Unitronics, S.A. andres@unitronics.es www.unitronics.es Introduction The politic change in some companies had a great influence in maintenance and operation works in their electric machines. Those, have seen many times a decrease in maintenance works allowing a cost decrease in a short term but generating a greater risk of use of them in a mean and long term. The operating conditions also have changed in the sense of taking the maximum advantage of each machine making it work at the maximum possible ratings and some times above nominal values. This situation trends to premature age the machine fleet and if those are not part of a minimum maintenance program detecting risk situations or load limitation, the resultant situation will lead in a mean time to an irregular manoeuvre field (breakdowns, forced outages, supply interruptions…) that today are so usual and negative to the end customer. FIG 1. Breakdown of the dielectric system in a power transformer column. Courtesy from Electric Works Molina, Córdoba. Power transformer is an electric machine with a useful life cycle of some 30 years. This doesn’t mean to say that cannot be used above this time, in fact, a great part of the electric and industrial fleet is being operated with reliable machines above this time. The really important fact is to know the status and evolution of the transformer to be in conditions to operate it with the maximum security and know if it is appropriate to continue it’s use, know overload capacity, limit load, refurbish it or either take it out from active service. There i