Distance between power cables: PUE regulations and practical recommendations
When laying cable lines, one of the key issues determining the safety and reliability of operation is compliance with standardized distances between conductors. A correctly selected distance between power cables allows avoiding dangerous heating during parallel operation, reducing electromagnetic influence, providing access for maintenance and repair, and preventing damage to adjacent lines in the event of an accident on one of them. This guide summarizes the basic requirements regulated by the Electrical Installation Rules (PUE), building codes, and practical installation experience.
1. Regulatory framework
The main requirements for distances when laying cable lines are contained in the following documents:
- PUE, Chapter 2.3 “Cable lines with voltage up to 220 kV” (clauses 2.3.86–2.3.90).
- GOST R 53315-2009 “Cable products. Fire safety requirements”.
- SP 76.13330.2016 “Electrical devices” (updated version of SNiP 3.05.06-85).
- Guiding documents of organizations (e.g., instructions for cable line installation).
All values given below are the minimum permissible. When designing and installing, one should strive to comply with them, and in cramped conditions, apply additional protective measures.
2. Distances between power cables in a trench
Most often, cable lines are laid in the ground using the trench method. The regulation of distances between power cables in a trench is due to the need for heat dissipation, preventing damage during mechanical impacts, and facilitating subsequent repair.
| Installation conditions | Minimum clearance distance, mm | Note |
|---|---|---|
| Between cables up to 10 kV (including control cables) | 100 | If cables are unarmored and unshielded — the distance may be increased to 250 mm. |
| Between cables 20–35 kV | 250 | — |
| Between cables of different organizations (owners) | 500 | By agreement, a reduction to 250 mm is allowed. |
| Between power cables and communication cables | 500 | If impossible to comply — shielding or separating partitions. |
| From cable to parallel utilities (pipelines, heating mains) | 1000–2000 | Depends on the type and temperature of the coolant. |
No more than six cables may be laid in one trench. If the number is greater, it is recommended to construct separate trenches or use cable blocks and collectors.
When laying cables in parallel at crossings over railways, highways, and also in places where mechanical damage is possible, the distances between them within the protective zone must be at least 250 mm (for cables up to 10 kV) and 500 mm (for cables 20–35 kV).
3. Distance between parallel laid power cables in trays and on cable structures
Distance between power cables in a tray is determined not only by PUE regulations but also by fire safety requirements and cooling conditions. When installing openly (on trays, in boxes, along walls), gaps must be provided to allow heat dissipation and prevent fire spread.
| Installation type | Minimum clearance distance, mm | Additional conditions |
|---|---|---|
| Between single cables in trays (unarmored) | 25–50 | Usually equal to the cable diameter, but not less than 25 mm. |
| Between groups of cables (bundles) in trays | 100 | To ensure fire safety and access. |
| Between cables on cable shelves (in one row) | 10–20 | Essentially — laying closely, but considering permissible current load. |
| Between different types of cables (power and control/communication) | 100–200 | To reduce electromagnetic influence — shielding or separation by a partition. |
| From cable to metal structures (trays, boxes) | — | Insulation is not required if the cable has a sheath that withstands the voltage. |
When laying in multiple layers, the distance between layers must be at least 100–150 mm to ensure cooling. Fire safety requirements must also be observed: for non‑propagating flame cables (ng), denser laying is allowed, but with consideration of current derating factors.
4. Distances in collectors, tunnels and channels
In cable structures (collectors, tunnels, channels), the standards for distances between parallel power cables are set depending on the voltage and type of insulation. Requirements for providing access for installation and repair also apply here.
- Between power cables with voltage up to 10 kV laid on structures, the clearance distance must be at least 35 mm (for single‑core) and 50 mm (for multi‑core).
- For cables 20–35 kV — at least 100 mm.
- In collectors and tunnels, cables should be arranged so that a passage at least 0.8 m wide remains between them and the building structures for maintenance.
- With a two‑row arrangement of cables on both sides of the passage, the distances between cables in one row may be reduced to 10–20 mm provided the permissible current loads are maintained.
According to the PUE, it is forbidden to lay power cables together with pipelines of flammable liquids and gases in cable structures. The distance to heat pipelines must be at least 1 m, and if impossible, thermal insulation must be provided.
5. Distance between power cables at crossings and approaches
When cable lines cross each other or other utilities, the distances are regulated separately.
- When two cable lines with voltage up to 35 kV cross, the crossing angle should be close to 90°, and the clearance distance must be at least 250 mm.
- When crossing heat pipelines or pipelines with flammable liquids, the distance must be at least 500 mm, and the cable must be protected from mechanical damage (pipe, box).
- When crossing highways and railways, cables are placed in pipes or blocks over the entire width of the protective zone, with the distance between cables within the crossing being at least 250 mm.
6. Features for cables with different insulation classes and armor
When determining the distance between parallel laid power cables, it is important to consider the design:
- Armored cables (VBbShv, AVBbShv) can be laid with smaller distances (up to 100 mm), as the steel tapes provide additional protection and facilitate heat dissipation.
- Unarmored cables (VVG, AVVG) require increased gaps (from 100 to 250 mm) to prevent damage from external influences and to ensure normal cooling.
- Cables with cross‑linked polyethylene insulation (XLPE) allow smaller distances due to higher thermal resistance, but the electromagnetic compatibility standards remain the same.
7. Influence of installation method on permissible distances
When selecting distances, it is also necessary to consider that installation in ground, air, water, or inside buildings creates different thermal conditions. In this regard, the PUE recommends:
- When laying in the ground, distances may be slightly smaller than in air due to better heat dissipation.
- When grouping cables in trays or boxes, correction factors to the continuous current ratings specified in GOST 31996-2012 should be applied. The factor depends on the number of adjacent cables and the distance between them.
- When laying in pipes or blocks, the distance between cables is determined by the block design (usually 30–50 mm between ducts).
8. Practical recommendations
- Before starting installation, draw up a route diagram indicating all parallel lines and crossings. Mark distances according to PUE requirements.
- If space is limited, reducing distances is allowed provided protective measures are applied: installation of separating partitions, use of shielded cables, use of cables with the “ng” index to reduce fire hazard.
- When laying power and control cables together, be sure to comply with the standards for distance between power cables and communication lines specified in the PUE (at least 500 mm), or use shielding.
- All distances are measured as clearances between the outer sheaths of the cables.
- After completing installation, perform control measurements (including insulation resistance) and prepare as‑built documentation with references.
9. Conclusion
Compliance with standardized distances between parallel laid power cables is a mandatory condition for safe and long‑term operation of cable lines. Deviations from PUE requirements are permissible only with a feasibility study and additional protective measures. When designing and installing, it is necessary to consider not only the minimum distances, but also the conditions of heat dissipation, mechanical strength, operational convenience, and fire safety.
For critical facilities (industrial enterprises, residential complexes, buildings with large numbers of people), it is recommended to use cables that comply with GOST and have certificates. A wide range of power cables of various types (VVGng‑LS, VBbShv, AVVG) is presented in the catalog of JSC “Kazenergocable”. If necessary, our specialists will help calculate the optimal distances and select a power cable taking into account the installation conditions. You can see the large selection of cables on the plant’s website.
