7 Tips From the Transformer Doctor

Make sure that your on-load tap-chang­ers are under­go­ing main­te­nance at the appro­pri­ate inter­vals. The date of a next main­te­nance appoint­ment will depend on how long it has been in use or how many switch­ing oper­a­tions it has per­formed. As an exam­ple, some tap-chang­er types may be due for main­te­nance after sev­en years or 70,000 switch­ing oper­a­tions, which­ever comes first.

Per­form­ing main­te­nance on a trans­former is a job for an expert—not just any tech­ni­cian will be famil­iar with the spe­cif­ic demands that trans­form­ers and tap chang­ers pose. Hav­ing main­te­nance per­formed by qual­i­fied staff will make it pos­si­ble to iden­ti­fy any irreg­u­lar­i­ties in oper­a­tion ear­ly on.

Check the oil at least once a year. The state of the oil can shed some light on the fit­ness of a transformer—just like a blood test can give a doc­tor insights into a patient’s health. For exam­ple, low water con­tent, high sur­face ten­sion, a high lev­el of dielec­tric strength, and a low pow­er fac­tor are all indi­ca­tors of good oil qual­i­ty.

An even more in-depth analy­sis involves an addi­tion­al inves­ti­ga­tion of the gas­es. We rec­om­mend per­form­ing such a dis­solved gas and oil Analy­sis (DGA) once a year. This involves check­ing the ratio of dis­solved gas­es in the oil. Each of the gas­es is gen­er­at­ed in the trans­former by a cer­tain state or cer­tain con­di­tions. Once the analy­sis is com­plete, we can tell whether the trans­former is in good con­di­tion.

Each oil cham­ber must have enough oil in it, so it is impor­tant to check the lev­els. This includes the main tank, the on-load tap-chang­er con­tain­er, and the bush­ings. Check­ing oil lev­els is impor­tant because the oil acts as an insu­lat­ing mate­r­i­al, coolant, and lubri­cant all at the same time.

Check the dehu­mid­i­fi­ca­tion unit reg­u­lar­ly to ensure that no imper­mis­si­ble mois­ture is enter­ing the oil expan­sion ves­sel from the out­side, because mois­ture in the oil will short­en the transformer’s ser­vice life. Have an expert check whether the device is work­ing reli­ably. It may be that the sil­i­ca gel—which is vital for remov­ing water—needs to be replaced.

Reg­u­lar inspec­tions are extreme­ly impor­tant. Our spe­cial­ists check all of the installed components—including bush­ings, fans, dis­plays, valves, motor-dri­ve units, and con­trol cabinets—for issues such as leaks or cor­ro­sion in order to detect them ear­ly on. Func­tion checks on pro­tec­tive devices allow us to ensure that the trans­former will switch off imme­di­ate­ly in the event of a fault.