Safe distance from power overhead lines

Nowadays, all companies operating in the field of construction of power and telecommunications networks are obliged to comply with applicable standards and laws. On the other hand, every aspect of security should be foreseen already at the stage of designing the energy infrastructure. Professional companies dealing with the construction of energy networks must carry out the investments commissioned to them in accordance with applicable standards. An important aspect that we want to draw attention to in the following text is the issue of keeping a safe distance from power lines. This is extremely important already at the stage of designing and building power grids.

Safe distance from power lines — applicable standards

Each company, when building a power line, must comply with the provisions contained in the standards. They contain a number of useful information that affects the safety of its users. In this regard, it is worth paying attention to the standards used in Poland, which contain information on the distance from overhead power lines that should be kept and how it is determined:

1. PN-EN 50341-1:2013-03 – it contains general requirements and specifications for overhead alternating current (AC) power lines above 1 kV.
2. PN-EN 50341-2-22:2022-06 – part two of the standard concerning national normative conditions for Poland. Applies to AC overhead power lines above 1 kV.
3. SEP N SEP-E-003 – defines the rules for the design and construction of AC overhead power lines with fully insulated and semi-insulated conductors.
4. PN-E-05100-1:1998 – concerning overhead power lines and their design and construction.

These are the most important standards that every company designing overhead power lines must pay attention to. So how is the distance to overhead power lines calculated?

Safe distance from overhead power lines above 1 kV

The first important aspect in the design and construction of power lines is to maintain safe distances of vertical power line wires when crossing with a building at the greatest overhang. According to the PN-E-05100-1:1998 standard, they are determined from the following formulas:

• O = 5+U/150 distance from an easily accessible and flammable part of the building
• O = 3,5 + U/150 distance from the hard-to-reach and hardly flammable part of the building

In the formulas above:

O — safe distance in [m]
U – rated line voltage [kV]

Another aspect is the safe distance from the building in case of approaching an unearthed conductor. It is the minimum:

• O = 1+ U/150 with the wind
• O = 1+ (b/2) + (U/150) in windless weather from hard-to-reach parts of the building and the edge of the roof
• O = 2+ (b/2) + (U/150) in windless weather from easily accessible parts of the building and the edge of the roof

Where b is the distance between the line wires [m].

It is also worth determining the distance of the unearthed wire of the overhead power line from each point of the upper branches of a tree:

• O = 2,5 +U/150+s in this case, the assumption is windless weather and standard cable sag

Design and construction of overhead power lines according to the SEP N SEP-E-003 standard

The SEP standard defines the requirements for the design and construction of overhead power lines with insulated conductors. In this range, distances have been determined. In the case of lines with fully insulated conductors up to 1 kV, the minimum values are:

• 0.2 m if the cable is located in a hard-to-reach parts of the building
• 1 m in the case of a distance from a balcony, terrace or window

However, in the case of tree trunks and branches, the following distances should be maintained:

• minimum 0.5 m in the case of a power line with fully insulated conductors
• minimum 1 m if we are dealing with a power line with semi-insulated conductors

Keeping a safe distance from power lines

Undoubtedly, every professional company dealing with the design, construction or service of power lines uses current standards. It must also act in accordance with applicable laws. The safe distances from power lines presented above are only a small part of these regulations. Maintaining safe distances from power lines is only one of many important aspects that must be taken into account when building the entire power infrastructure.