What Is a Power Line: High-Voltage Lines, Components and Pole Types

Power lines: overhead and underground

In Ukrainian the usual abbreviation is LEP, short for «лінія електропередачі». English uses «power line» or «transmission line». All of these name the structure that carries electricity from power plants and substations to consumers.

There are two kinds. On an overhead line the wires run in the open air and are fixed to poles through insulators and fittings. On a cable line the cables lie in the ground, in water or inside buildings. When people say «power line» they usually mean the overhead kind: it is the one you see along roads and fields.

A cable line is chosen where an overhead line will not fit on a cramped site or does not suit the architecture. The rest of this article is about overhead lines, because only they have poles.

What an overhead line is made of

The line behaves as one system: the poles are tied together by conductors and ground wires, so a load on one element is passed on to the others. The parts are these:

• poles with foundations hold everything else at the right height and carry wind, the weight of the conductors and ice;
• conductors carry the current; a three-phase circuit has three phases, and on lines of 330 kV and above each phase consists of several conductors;
• the overhead ground wire is strung above the conductors and takes lightning strikes. Not every line has one;
• insulators separate the conductors from the pole: suspension insulators are joined into strings, pin insulators sit on the cross-arm;
• line fittings: clamps, connectors and other parts that hold a conductor to its insulators and a ground wire to the pole;
• earthing leads lightning current and fault current into the ground. The resistance required depends on the soil and the pole type.

The codes set their own design cases for each of these elements. How wind, ice and temperature act on them is covered in Loads on Overhead Lines and Power Line Poles.

Voltage classes and the poles used on them

Line voltage is nominal, meaning the voltage between two conductors of a three-phase line. PUE (2026 edition), cl. 1.2.21, gives the classes after DSTU EN 60038: low voltage up to 1 kV, medium voltage over 1 up to 35 kV, high voltage over 35 up to 230 kV and extra-high voltage over 230 kV. Lines of 6 and 10 kV belong to distribution networks.

Pole heights for each class are discussed in Power Line Pole Height by Voltage Class; the table gives ranges only.

For lines of 35 kV and above the table names steel poles, but reinforced concrete poles are used there too. Some sources put 330 kV in the high-voltage class. The full height of a pole with its ground-wire peak is greater than the height to the underside of the cross-arm; the height of 0.4–10 kV poles depends on the shaft and the design.

Types of power line poles

Poles are told apart by their place on the route and by their construction.

By place on the route, suspension poles stand on straight sections and only support the conductors. Tension poles fix the conductors rigidly and hold the difference in pull, angle poles stand where the route turns, and terminal poles close the line at its start and its end. Suspension poles are the most numerous: according to the article on pole types by purpose they make up 80–90% of all poles on a line.

By construction, poles are reinforced concrete, steel lattice or steel multi-sided. Reinforced concrete is traditional for low and medium voltages. Lattice poles of angle sections remain common on high-voltage lines in open country. A multi-sided pole is a single bent shaft with a closed profile, and it needs only a small plot for its foundation. Which to choose, and when, is compared in Power Line Poles: Multi-Sided, Lattice or Reinforced Concrete.

The POLYGONAL company makes steel poles for overhead lines; they are described on the power line poles page.

High-voltage lines and the protection zone

«High-voltage line» is an everyday phrase, and PUE (2026 edition), cl. 1.1.3, does not define it as a term. People normally mean lines above 1 kV, since PUE uses that limit to split electrical installations. If the high-voltage class under DSTU EN 60038 is meant, these are lines over 35 up to 230 kV.

A protection zone runs along the route: a strip of land where construction, tree planting and other work that could endanger the line are restricted. Its width is measured horizontally from the projection of the outermost conductors and grows with voltage. Widths by class, distances to buildings and conductor height above ground are in Power Line Protection Zone.

What decides the choice of pole

A pole is chosen for a specific route. The starting point is the voltage class: it sets the distances from the conductors to the ground and between conductors, and so the height of the pole.

Climate comes next. Wind, ice and temperature set the design cases against which both the pole and its foundation are checked. Ice has its own article: Ice, Rime and Wet Snow on Power Line Conductors.

The third factor is span length. PUE gives no fixed figure per voltage class; it is found by calculation for each line, as the article on the distance between poles explains. A short span relieves every pole, but more poles are needed.

The number of circuits on the pole (single or double) and the conditions along the route also count: open country, built-up areas, crossings of roads or other lines.

Power line poles from the manufacturer

If you need the poles themselves rather than the theory: POLYGONAL makes power line poles for 6–220 kV from steel multi-sided shafts with hot-dip galvanising. For 110 kV lines see the separate page on multi-sided poles for 110 kV overhead lines: types, applications and what is needed to price them.