Most high voltage power lines run on a delta configuration with three phases and no neutral. Now if there isn’t any neutral (due to the nature of it being a delta system) then how can the power line be effectively earthed?

In other words, as far as I know, if you measure line to earth voltage you will find exactly the line voltage (as if earth is 0v), or do you? When searching for earthed delta configurations I have found two ways, one called “centre tap” and the other one “two-leg tap” which are illustrated below:

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Are any of these methods employed in high voltage lines? If so, that won’t guarantee that that you’ll get the line to earth voltage equal to that of the line voltage on all phases.

The question is then, how exactly are high voltage (delta) lines earthed?

  • \$\begingroup\$ Are you assuming that the use of a wye transformer is prohibited? \$\endgroup\$
    – Andy aka
    Commented Jul 25, 2020 at 10:55
  • \$\begingroup\$ I'm a bit confused: Why would you want to ground a high-voltage line? These run over long stretches of land, and "ground potential" is a local concept... \$\endgroup\$ Commented Jul 25, 2020 at 11:01

1 Answer 1


High voltage transmission lines are NOT delta connected. They are almost exclusively grounded configurations (fed from grounded-wye windings) in North America and elsewhere. Just because you only see 3 phases and no neutral on the right-of-way doesn't make it delta configuration. At distribution levels it is also largely grounded-wye. There are resonant grounded distribution systems that use grounded-wye source transformers with Peterson coil in neutral. There are also delta configurations. These later two more prevalent outside North America. Of course you can always find exceptions as well.

Transistor shows a link above that discusses differences in distribution between North America and Europe. Check it out.


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