Substation and Switchyard Lightning Protection under the PUE (2026 Edition): Lightning Rods, Masts, Earthing

Where the PUE requires protection against direct strikes

Open switchyards (called ORU in Russian, VRU in the Ukrainian PUE) from 15.75 to 750 kV and substations from 35 to 750 kV must be protected against direct lightning strikes; the same goes for the buildings of indoor switchgear (ZRU) and enclosed substations (ZPS). The protection takes account of the technological features of the site and the requirements of DSTU EN 62305 (PUE (2026 edition), cl. 4.2.162).

There are two exceptions: open 35 kV substations with transformers of up to 1.6 MVA each (however many there are), and open 3–20 kV substations with transformers of any rating, need no protection against direct strikes.

This is about direct strikes. Surge waves coming in along a line are handled separately by surge arresters, which are outside the scope of this article.

What is used: rods, wires, tall structures

Switchyards and substations are protected against direct strikes and against lightning surges arriving along the lines. For this, rod and wire lightning rods are installed, together with earth wires on the line approaches; the PUE also lists surge arresters, but they are not lightning rods (cl. 4.2.161).

Switchyards from 15.75 kV are protected by rod lightning rods, either free-standing or on the structures of the switchyard itself. The shielding effect of tall structures may also be used: line towers, floodlight masts, radio masts (cl. 4.2.163).

The difference between a lightning conductor, a lightning rod and an air terminal is explained in the article on lightning protection terms.

A lightning rod on a switchyard structure: soil, earth electrode, rods

A rod lightning rod on a structure of a switchyard from 15.75 kV may be installed only where the soil allows it. With an equivalent soil resistivity in the thunderstorm season up to 500 ohm·m, the area of the substation earth electrode does not matter. Above 500 ohm·m the substation earth electrode must cover 10,000 m² or more (cl. 4.2.163).

Then come the earthing requirements. From the post carrying the lightning rod (switchyards of 15.75–150 kV) the current must spread through the earth electrode in at least two directions, at least 90° apart between neighbouring ones. Vertical electrodes 3–5 m long are added: at least two for 15.75 and 35 kV, one for 110 and 150 kV. On switchyards of 220 kV and above they may be left out.

On 15.75 and 35 kV gantries with rod lightning rods, insulator strings rated for 110 kV are needed. The air gap from the structure to live parts must be no less than the length of the insulator string.

The figures for 35–150 kV gantries are collected in the article Multi-sided switchyard gantries 35–150 kV, and the gantries themselves are covered on the switchyard gantries page.

Transformer gantries: stricter conditions

If a lightning rod stands on a transformer gantry, a shunt-reactor gantry or a structure less than 15 m from a transformer or reactor along the earth electrode, the conditions are stricter (cl. 4.2.164). The equivalent soil resistivity in the thunderstorm season must not exceed 350 ohm·m.

• surge arresters on the MV and LV winding terminals (3–35 kV) of the transformer, or no more than 5 m away along the busbar;
• current spreading from the post in three or four directions, at least 90° between them;
• one vertical electrode 3–5 m long on each direction, 3–5 m from the edge of the post foundation;
• on a substation with a 35 kV HV side and a lightning rod on the transformer gantry, an earth resistance of no more than 4 ohms, with earth electrodes outside the switchyard electrode not counted;
• the earthing conductors of the arresters and the transformer connected close together, or so that the arrester connection lies between the gantry with the lightning rod and the transformer.

Free-standing lightning rods and floodlight masts

Where lightning rods may not be installed on switchyard structures, separate lightning rods are used (cl. 4.2.165). The air distance to live parts is calculated as S ≥ Af(z.g) + 0.12·R, where Af(z.g) is the smallest clear distance between live and earthed parts for flexible busbars and R is the earth resistance of the lightning rod (check the formula against the PUE text).

A separated earth electrode for a lightning rod must not exceed 10 ohms. If the distances to the switchyard electrode and to equipment are not kept, or the resistance exceeds 10 ohms, the lightning rod is connected to the substation earth electrode. The calculation of distances and resistance is shown in the article on the steel mast as an air terminal.

A floodlight mast on a substation site is the same case: its earth electrode is also connected to the substation electrode under the conditions of cl. 4.2.163, and what to add when they cannot be met is set out in the article on the 30 m floodlight mast.

Wiring for lighting and antennas on a lightning rod or mast is made with metal-sheathed cable, or with unsheathed cable in a metal pipe. The sheath or pipe is earthed, and near the structure the cable is laid directly in the ground for at least 10 m (cl. 4.2.167).

Wire lightning rods and line approaches to the substation

Wire lightning rods of lines of 110 kV and above may be connected to earthed switchyard structures; from the post, current spreads in two or three directions at least 90° apart (cl. 4.2.166). For 35 kV lines the same limits on soil and earth electrode area apply as for rods on structures, plus one 3–5 m electrode in each direction, at least 5 m from the post foundation.

Wire air terminals and lightning rods must not be installed on the end towers of 6–20 kV lines. The earth electrodes of the 35 kV line towers nearest to the switchyard must not exceed 10 ohms.

Lines from 35 kV have lightning-protected approaches to the substation. They are normally made with an earth wire, and the length depends on the distance between the nearest surge arrester and the power transformer (tables 4.2.5–4.2.8, cl. 4.2.168).

For 35 kV lines: where the wire may not be connected to the switchyard, it ends at the support nearest to the switchyard, and the first span without a wire is protected by rod lightning rods on the substation, on supports or beside the line (cl. 4.2.166).

ZRU and ZPS buildings: roof, mesh, down-conductors

If the roof is metal, the building is protected by earthing the covering; with a reinforced-concrete roof whose elements are electrically continuous, the reinforcement is earthed. If there is neither, rod air terminals are fitted or a mesh is laid directly on the roof (cl. 4.2.162).

At least two down-conductors run from each rod on the building, preferably on opposite sides. The mesh is made of steel, aluminium or copper with a cross-section of at least 50 mm², with a mesh size of 5, 10, 15 and 20 m for protection levels I, II, III and IV.

Down-conductors from the mesh to the earth electrode run in at least two places, no more than 10 m apart (levels I–II), 15 m (III) or 20 m (IV) around the perimeter. Earthing conductors have a detachable threaded joint at no more than 1 m above ground level.

What to send for selecting a lightning rod on a shaft

The POLYGONAL company manufactures MO-series lightning rods on multi-sided shafts from 5 to 40 m tall, as well as floodlight masts. Substation lightning protection is designed by a design organisation, and we can help select a shaft for its solution.

To select one, send the switchyard voltage and structure type, the required height and location, the soil resistivity, the area of the substation earth electrode, and details of equipment on the mast (floodlights, antennas). Installation is done by a licensed construction partner company. Leave work at height and electrical connections to specialists.

The shaft catalogue is lightning rods 6–40 m, the overall picture is on the lightning protection page, and choosing a lightning rod for a mast is covered in Lightning protection of masts and towers.