Short Answer: The Key Property of a Cold-Resistant Cable
The key property of a cable for a cold climate is the ability to retain elasticity and electrical integrity at negative temperatures, including installation without pre-heating. The KhL (cold-resistant) design according to GOST 15150-69 ensures operation in the range from minus 60 °C to plus 50 °C, depending on the design. The EKhL (extra-cold-resistant) design extends the minimum installation temperature to minus 40 °C. For Kazakhstan, with winter temperatures down to minus 40–45 °C in the northern and central regions, the choice between KhL and EKhL is determined not only by the operating range but also by the minimum installation temperature.
Cold resistance is provided not by a single cable element but by a combination of insulation and sheath materials. Ordinary PVC compound loses flexibility at minus 15 °C, while specialised cold-resistant compositions retain elasticity at minus 60 °C. Therefore, the designation “KhL” in the marking refers to the climatic design of the entire cable, not only the sheath.
What Influences the Cable Must Withstand
For the climate of Kazakhstan, not only low temperatures are dangerous. An outdoor cable is exposed to a complex of influences, each of which affects the choice of design.
| Condition | Risk to the cable | What is required of the cable |
| Low operating temperature | Embrittlement of insulation and sheath, cracking during bending | Materials that retain elasticity at minus 60 °C |
| Low installation temperature | Destruction of insulation during installation and bending | Minimum installation temperature not higher than minus 30 °C (KhL) or minus 40 °C (EKhL) |
| Solar and UV radiation | Ageing of the sheath, loss of mechanical properties | UV-resistant sheath (for example, made of polyethylene or specialised PVC) |
| Humidity and precipitation | Moisture ingress into the insulation, reduction of resistance | Sealed design, hydrophobic filling |
| Mechanical influences (wind, snow, icing) | Tension, kinking, damage to the sheath | Armour, reinforced sheath |
| Rodents | Damage to the sheath | Armour of steel tapes or wires |
For cables laid in the ground at a depth below the freezing level, the soil temperature remains positive. However, at the entry into a building, on open sections of the route and during installation, the cable contacts cold air. Therefore, the KhL or EKhL design is required for outdoor installation and for sections where installation at negative temperature is possible.
Which Design Provides Protection
The cold resistance of a cable is determined by the insulation and sheath materials. Structural elements such as armour and screens protect against mechanical influences but do not affect the ability of the material to retain elasticity at low temperatures.
Insulation. For cold-resistant cables, insulation made of rubbers based on isoprene or butadiene rubber (types RShT-2, RShTM-2-KhL), cross-linked polyethylene (XLPE) or ethylene propylene rubber (EPR) is used. These materials retain dielectric properties and flexibility at negative temperatures. Ordinary PVC compound for insulation becomes brittle at minus 30 °C.
Sheath. For the outer sheath of cold-resistant cables, rubber compounds based on isoprene or butadiene rubber, polyethylene, polyurethane or specialised PVC compositions are used. An ordinary PVC sheath without cold-resistant additives is not intended for operation below minus 15 °C. A cross-linked polyethylene sheath retains flexibility down to minus 60 °C and is resistant to UV radiation.
Armour. Steel tapes or galvanised wires protect the cable from mechanical damage and rodents. Armour does not affect cold resistance, but for cables laid in trenches and on open sites, an armoured design is mandatory.
Hydrophobic filling. Filling the spaces between conductors with a hydrophobic compound prevents the spread of moisture along the cable when the sheath is damaged. For cables operating under conditions of temperature and humidity fluctuations, this is an important element.
If the cable must not propagate combustion or must maintain operability during a fire, the indices ng, LS, HF or FR are added to the cold-resistant design. Combinations of these properties are analysed in the materials: table of differences between LS, HF, LSLTx, FRLS and FRHF and fire-resistant and non-flame propagating cable. For damp rooms and outdoor installations, where smoke formation and toxicity of combustion products are important, the properties are tested separately: smoke, halogens and toxicity of a cable.
How to Choose a Suitable Cable
The selection algorithm is built from the operating conditions to the specific design.
- Determine the minimum operating temperature. For the northern regions of Kazakhstan, winter temperatures reach minus 40–45 °C. The KhL design is rated for operation down to minus 60 °C, which covers this range with a margin.
- Determine the minimum installation temperature. If installation is carried out at negative temperature, the permissible installation temperature is checked. For KhL it is minus 30 °C, for EKhL — minus 40 °C. Installation at a lower temperature requires pre-heating.
- Check the sheath material. Ordinary PVC is not suitable for outdoor installation in frost. A sheath made of rubber, polyethylene or a specialised cold-resistant composition retains elasticity.
- Take UV radiation into account. For open sections of the route, the sheath must be UV-resistant. Polyethylene and specialised compositions are resistant to solar radiation.
- Take mechanical loads into account. For installation in trenches and on open sites, armoured cables are used. For fixed installation, an unarmoured one is sufficient if the route is protected.
- Check the fire characteristics. If the cable is laid in buildings, the indices ng, LS or FR are added depending on the requirements of the facility.
The designation KhL or EKhL indicates the climatic design, but does not remove the need to check the specific characteristics of the cable according to the manufacturer’s documentation. Temperature ranges may differ for different types and designs. For example, a KG-KhL cable with rubber insulation and sheath is operated from minus 60 °C to plus 50 °C, while a cable with cross-linked polyethylene insulation in the KhL design operates in a similar range, but with different flexibility characteristics.
Where It Is Applied
Oil and gas facilities. At the fields of Kazakhstan, cables operate on open sites at temperatures down to minus 40 °C and below. Cables in the KhL design with a rubber or polyethylene sheath, armoured to protect against mechanical damage, are used.
Mining industry. Excavators, draglines and drilling rigs use flexible cables KG-KhL and KGE-KhL, rated for operation at minus 60 °C and dynamic loads when winding onto a drum.
Outdoor routes and open sites. For installation on trestles, in trays and along building walls outdoors, cables with a sheath resistant to UV and frost are used. For underground installation at a depth below the freezing level, the use of cables without the KhL index is permitted if the soil temperature is positive.
Industrial facilities with unheated premises. Warehouses, hangars and refrigerating chambers require cables that retain flexibility at negative temperatures. For such conditions, the KhL design with rubber insulation is suitable.
Mobile mechanisms and power tools. KG-KhL cables and similar ones are used to power mobile equipment at construction sites and in quarries. High flexibility is retained at minus 60 °C.
Typical Mistakes
Assuming that any cold-resistant cable is suitable for installation in severe frost. Operating temperature and installation temperature are different parameters. A cable may operate at minus 60 °C, but installation without heating is permitted only down to minus 30 °C or minus 40 °C, depending on the design. Installation at a lower temperature without heating leads to cracking of the insulation.
Using a cable with an ordinary PVC sheath for outdoor installation. Ordinary PVC loses elasticity at minus 15 °C and is not resistant to prolonged UV exposure. For open routes in Kazakhstan, a sheath made of a cold-resistant composition or polyethylene is required.
Ignoring UV resistance. A cable intended for underground installation may not have UV stabilisation. During open installation, the sheath breaks down under the influence of solar radiation within a few seasons.
Confusing the KhL and EKhL designs. KhL is rated for installation down to minus 30 °C, EKhL — down to minus 40 °C. For conditions where installation is carried out at minus 35 °C, KhL is not suitable; EKhL or pre-heating is required.
Choosing a cable only by the KhL designation without checking the documentation. Different manufacturers use different materials and indicate different temperature ranges for the same climatic design. The specific values are checked against the technical specifications and the cable passport.
FAQ
What is the difference between the KhL and EKhL designs?
KhL (cold-resistant) is a climatic design according to GOST 15150-69, ensuring operation at temperatures down to minus 60 °C and installation without pre-heating at a temperature not lower than minus 30 °C. EKhL (extra-cold-resistant) is an extended design permitting installation at a temperature not lower than minus 40 °C. The operating temperature for EKhL may also be lower depending on the design.
Can a KhL cable be laid at minus 40 °C?
Installation of a cable in the KhL design without pre-heating is permitted at a temperature not lower than minus 30 °C. At minus 40 °C, either pre-heating is required, or the use of a cable in the EKhL design, for which the minimum installation temperature is minus 40 °C. The specific values are checked against the manufacturer’s documentation.
Which sheath material should be chosen for outdoor installation in Kazakhstan?
For outdoor installation, sheaths made of polyethylene, cross-linked polyethylene or specialised cold-resistant PVC compositions are used. Polyethylene sheaths are resistant to UV and retain flexibility at low temperatures. Ordinary PVC is not suitable for open installation in a cold climate.
Is an armoured cable needed for installation in a trench?
For installation in the ground at a depth below the freezing level, the soil temperature is positive, and the cold resistance of the sheath is not critical. However, armoured cables are used to protect against mechanical damage and rodents. For sections where the cable comes to the surface or is laid in unheated premises, the KhL design is required.
What to do if a cable needs to be laid at a temperature below the permissible one?
Pre-heating of the cable to a temperature not lower than the permissible one for installation is applied. Heating is carried out in a heated room or using special equipment. An alternative is to use a cable in the EKhL design, if its minimum installation temperature corresponds to the conditions.
Sources
- GOST 15150-69 “Machines, instruments and other technical products. Versions for different climatic regions. Categories, operating, storage and transportation conditions as to the influence of climatic factors of the environment” — in force — official text on meganorm.ru — classification of climatic designs, including KhL and UHL.
- GOST 31565-2012 “Cable products. Fire safety requirements” — in force — official text on meganorm.ru — classification of cables by fire hazard.
- GOST 31996-2012 “Power cables with plastic insulation for rated voltages of 0.66; 1 and 3 kV” — in force — official text — requirements for the design of power cables, climatic designs.
- Technical specifications for KG-KhL, KGE-KhL cables — in force — manufacturers’ technical documentation — temperature ranges of operation and installation.
- Electrical Installation Code of the Republic of Kazakhstan 2015, as amended by the order of the Minister of Energy of the Republic of Kazakhstan dated 31.10.2022 No. 340 — in force — IPS “Adilet”, adilet.zan.kz — requirements for cable installation under various conditions.
