I sometimes see these devices along power lines when I'm driving and was wondering what they were. They look just like the regular transformers that I see on top of electrical poles, but it seemed strange to me that they each had two connections to the same phase overhead, so I though that maybe they're some sort of capacitor bank for filtering unwanted frequencies from the power lines, or something like that.

Does anyone know what these actually are? And if so, can you tell how and why they're connected in this arrangement?

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    \$\begingroup\$ They look like transformers. If those fuzzy things in between the connection points to the wires are to prevent arcing, my guess is the wires are not continuous, with one voltage entering on the left and another leaving on the right. I can't make out the overall connection between the phases though so I could be wrong. \$\endgroup\$ Feb 21, 2023 at 3:34
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    \$\begingroup\$ Whatever they are - they're beautiful! \$\endgroup\$
    – uhoh
    Feb 21, 2023 at 13:14

1 Answer 1


Those equipments are called 'voltage regulators'. It consists in an autotransformer (I would guess, 20% of the volume) and an on-load tap changer (the remaining volume). As the name says, it is used to allow the voltage to be steady in cases of long medium voltage distribution lines (10 to 36kV). Here in Brazil it's very common to have it in the entry of small cities or villages.


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