About 2 weeks ago we had a buch holtz alarm at T1 tapchanger in our Laingholm substation.
This is situated in the Western suburbs of Auckland NZ.
A bank of 2 transformers of 7.5 MVA supply Laingholm, Huia and Waitipu.
After investigating we found burnt and heavily pitted contacts at the TCOL ( Tap Changer On Load ).
This is the first time in over 40 years these have been serviced for contact renewal.
Photo's are in the Electrical photo galleria.
Regards from Raymond