Attached below is an image of a Power transmission pole. What I am interested in is the cylindrical shaped objects attached to the transmission tower.

enter image description here

Some other observations and relevant information:

  1. These objects are not present in every tower but on one in every few towers or so.

  2. These towers are from a mixed Residential and commercial neighborhood

  3. The towers in question are in Japan. I have not observed these cylindrical objects on similarly sized transmission towers in my Home country

  4. A less relevant observation is that even though these are overhead transmission lines, they are insulated, perhaps because of the proximity of the houses and buildings to the towers

    EDIT: There is a similar question linked here, however, this picture has both a single phase and larger 3 phase transformer while this earlier question had only a single phase one. Further, the question uses different terminology to describe the transformer (cylinder vs canister)

  • 7
    \$\begingroup\$ I see several cylindrical objects. \$\endgroup\$
    – Andy aka
    Jun 11, 2019 at 14:08
  • 6
    \$\begingroup\$ The largest gray cylinders close to the center of the picture are transformers. \$\endgroup\$
    – Dave Tweed
    Jun 11, 2019 at 14:14
  • 3
    \$\begingroup\$ Possible duplicate of What is this canister at the top of a utility pole? \$\endgroup\$ Jun 12, 2019 at 11:52
  • 1
    \$\begingroup\$ There's a good chance that these are also present on local utility poles in your home country and you just never noticed them. \$\endgroup\$
    – zwol
    Jun 12, 2019 at 15:06

4 Answers 4


Those look like transformers to me.

I don't know for sure but I strongly suspect that the top wires are the high voltage distribution and the middle ones are low voltage distribution. I'm not sure about the bottom ones, maybe communications cables.

Countries with a lower final distribution voltage are likely to have more smaller transformers, while those with a higher final distribution voltage are more likely to have fewer larger transformers. Larger transformers are more likley to be ground mounted while smaller ones are likely to be pole mounted.

I belive this is why you see lots of pole mounted transformers in some countries and realtively few in others (here in the UK you only see them in rural areas).

  • \$\begingroup\$ Accepted for explaining an implied part of the question. Why aren't such pole mounted transformers common elsewhere \$\endgroup\$
    – ijuneja
    Jun 14, 2019 at 2:03

I'm assuming you mean these two:

enter image description here

The official name for these is "Distribution transformer".

They are the "local transformers", here's a schematic of how they could be connected:

enter image description here

Which is from this question

Actual connections and voltages depend on the country so details may be different.

  • 4
    \$\begingroup\$ Nice diagram. Thanks for the attribution. ;^) \$\endgroup\$
    – Transistor
    Jun 11, 2019 at 18:15
  • 5
    \$\begingroup\$ @Transistor I agree, very clear diagram, could not have drawn it any better so that's why I re-used it :-) \$\endgroup\$ Jun 11, 2019 at 19:27
  • \$\begingroup\$ I see 2 different transformers in the picture and only 1 transformer in the drawing, right? \$\endgroup\$
    – Mast
    Jun 13, 2019 at 6:13
  • \$\begingroup\$ @Mast that is correct. \$\endgroup\$ Jun 13, 2019 at 6:23
  • \$\begingroup\$ @Bimpelrekkie, you might also mention that those in particular are generally referred to as pole top transformers. They may not always be seen because underground power would use pad mount transformers. \$\endgroup\$
    – Ben
    Jun 13, 2019 at 12:23

The large cylindrical devices as indicated below are power line transformers. Their function is to step down the higher distribution AC voltage down to the common mains line voltages that feed into residences and businesses.

enter image description here


The larger DT is 3 phase voltage stepdown, while the smaller one uses only 1 phase for local use residential use.


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