We recommend that the tap changer be operated several times on a full range of taps once a year to ensure that any deposits are removed from the contact area.

In case annual maintenance is not possible and the tap changer has not been used for many years, it is recommended to operate the tap changer approximately 20 times on a full range of positions before changing the tap.

Measuring the resistance of the phases before and after the self-cleaning maintenance operation described above would help check its efficiency.