Introduction: two insulation materials
Insulation determines the key operational parameters of a cable: permissible conductor temperature, resistance to short‑circuit currents, service life and installation conditions. In low‑ and medium‑voltage power cables up to 10 kV, two main types of insulation compete: polyvinyl chloride compound (PVC) and cross‑linked polyethylene (XLPE). The former forms the basis of mass‑produced series VVG, AVVG, VBbShv; the latter — of power cables with the index Pv, for example, PvVG, PvBbShv, PvP.
Cables with PVC insulation are manufactured according to GOST 31996, with XLPE — according to GOST R 55025 (for 10 kV) and related specifications. Basic information on the design of power lines and their classification is given in the overview about power cables. Recommendations for laying, taking into account bending radii and installation methods, are covered in the material cable laying.
Comparative table of PVC and XLPE
| Parameter | PVC compound | Cross‑linked polyethylene (XLPE) |
| Continuous permissible conductor temperature | 70 °C | 90 °C |
| Maximum temperature during short circuit (up to 5 s) | 160 °C | 250 °C |
| Installation temperature without preheating | −15 °C | −20 °C |
| Dielectric strength | High | Very high, low dielectric losses |
| Service life at rated load | 25–30 years | 30–40 years |
| Resistance to moisture and chemicals | Good | Excellent, non‑hygroscopic |
| Halogen release during combustion | Contains chlorine, releases HCl and dense smoke | Halogen‑free, low‑smoke |
| Fire‑safe versions | ng(A)-LS, ng(A)-FRLS | ng(A)-LS, ng(A)-HF (halogen‑free) |
| Flexibility and bending radius | Radius 7.5–10 D, moderate stiffness | Radius 7.5–10 D, more elastic in cold |
| Cable cost | Lower | 20–50% higher |
| Main application | Internal wiring, 0.4 kV distribution networks | 1–10 kV trunk lines, laying in difficult conditions, facilities with high heating requirements |
Thermal characteristics and current ratings
The main advantage of XLPE over PVC is its higher heat resistance. The continuous conductor temperature of a cable with PVC insulation must not exceed 70 °C. Under overloads and short circuits, the material softens and loses its dielectric properties. XLPE operates stably at 90 °C and withstands up to 250 °C in emergency modes. This gives an XLPE power cable a higher current‑carrying capacity for the same conductor cross‑section: according to the PUE, the permissible current for an XLPE cable is 10‑20% higher than for its PVC counterpart.
For 10 kV networks, this difference becomes critical. The Pv power cable for 10 kV with XLPE insulation can carry more power without increasing the cross‑section. In addition, lower losses in the insulation reduce heating and improve the overall energy efficiency of the line.
Dielectric properties and service life
Cross‑linked polyethylene has lower dielectric losses, especially at high frequencies and voltages. In 10 kV networks, this reduces the reactive component of leakage current and extends the service life of the insulation. PVC is subject to ageing over time: under the influence of heat and electric field, plasticisers migrate, and the insulation becomes brittle. XLPE contains no plasticisers, its structure is stable, so an XLPE power cable lasts 35‑40 years, while PVC lasts up to 30 years.
The moisture resistance of XLPE is higher: it is non‑hygroscopic and does not swell in water. This allows cables with XLPE insulation to be laid in wet soils without additional sealing. PVC compound is also water‑resistant, but prolonged exposure to water with dissolved salts accelerates its degradation.
Flexibility, bending radius and installation
PVC hardens at sub‑zero temperatures, so installation at −15 °C requires preheating. XLPE remains elastic down to −20 °C. The bending radius for both types is similar — 7.5‑10 outer diameters, but cables with XLPE insulation bend more easily without damaging the insulation layer. This simplifies entry into switchboards and laying along routes with turns.
Stripping and termination of PVC insulation is simpler: no special tools are needed to remove the semiconductive layers required for 10 kV cables. Medium‑voltage XLPE cables require more skilled installation and the use of heat‑shrink joints. Instructions for the installation of all types of power lines are given in the article cable laying.
Fire safety and smoke emission
PVC contains halogens — chlorine. When burning, it releases dense black smoke and hydrogen chloride, which, when combined with water, forms hydrochloric acid. This is dangerous for people and equipment. Flame‑retardant versions ng(A)-LS reduce smoke emission but do not completely eliminate halogens. XLPE is a halogen‑free material and releases significantly less smoke and toxic gases during combustion. That is why, for facilities with large numbers of people and for fire protection systems, cables with XLPE insulation in HF (halogen‑free) versions are often required. Information on fire safety standards for power cables is given in the article fire‑resistant cable.
Cost and economics of a cable line
The price of a cable with PVC insulation is lower. For typical in‑shop wiring or residential sector, this difference is often decisive. For the same conductor cross‑section, an aluminium or copper cable with PVC sheath and insulation is 20‑30% cheaper than its XLPE counterpart. A comparison of aluminium and copper conductors in terms of budget and conductivity is given in the material difference between copper and aluminium cable.
However, on long trunk lines and in 10 kV networks, lower losses and higher permissible current of an XLPE cable allow choosing a smaller cross‑section, which partially compensates for the price difference. Taking into account a longer service life and reduced maintenance costs, the total cost of ownership of an XLPE line is often lower.
When to choose a cable with PVC insulation
- Internal wiring in apartments, houses, offices — the ambient temperature does not exceed 25‑30 °C, currents are stable.
- 0.4 kV distribution networks with moderate loads. Here, aluminium and copper cables VVG, AVVG, VBbShv cover all needs.
- Facilities with a limited budget where no increased requirements for heating and fire safety are imposed.
- Temporary and seasonal lines — saving on material with a short service life.
When to choose a cable with XLPE insulation
- Medium‑voltage trunk lines of 10 kV. The Pv power cable with aluminium or copper conductors is the standard for such networks.
- Power supply to heavy equipment with high inrush currents and frequent overloads — XLPE withstands greater thermal loads.
- Laying in the ground and in high‑humidity conditions. XLPE is not subject to water degradation and does not require additional protection.
- Fire‑safe zones, escape routes, shopping centres — low smoke and absence of halogens are important. HF versions ensure air purity during a fire.
- Facilities with a long service life — bridges, tunnels, substations where cable replacement is difficult. The service life of XLPE is one and a half times longer.
Recommendations for selecting insulation type
| Operating conditions | Preferred insulation | Justification |
| Residential house, apartment | PVC (VVG, VVGng) | Sufficient heat resistance, low cost |
| Office building | PVC ng‑LS | Fire safety without cost increase |
| Industrial workshop with normal environment | PVC or XLPE | Depends on current loads and budget |
| 10 kV cable line | XLPE (PvP, PvV) | Requirement of GOST R 55025, high thermal resistance |
| Underground route in wet soil | XLPE | Excellent moisture resistance, long service life |
| Escape routes in shopping centres | XLPE ng‑HF | Halogen‑free, low‑smoke |
Typical mistakes when choosing insulation
- Laying a cable with PVC insulation in 10 kV networks — the PUE does not allow this. For medium voltage, XLPE is required.
- Ignoring the temperature regime: long‑term operation of PVC at 80‑85 °C reduces its service life several times. If the load is high, XLPE is needed.
- Choosing a cable solely by price, without considering the difference in permissible currents. A cheaper PVC cable may require a larger cross‑section, and the saving will be nullified.
- Using an XLPE cable without earthing the screen at both ends. This nullifies its advantages in electromagnetic compatibility.
- Laying a PVC cable without preheating at −20 °C — there is a high risk of cracks in the insulation.
- Forgetting that the marking “Pv” indicates XLPE. Confusion with PVC analogues leads to the purchase of an inappropriate cable.
Frequently asked questions
What is the difference between PvVG and VVG cables?
PvVG is a power cable with XLPE insulation and a PVC sheath. VVG is a cable with PVC compound insulation. The former has a higher permissible conductor temperature and short‑circuit resistance, the latter is cheaper and easier to install.
How to distinguish XLPE from PVC visually?
Marking on the sheath: the letter “Pv” at the beginning indicates XLPE. The absence of “Pv” and the presence of “V” in the first position indicate PVC. Visually, XLPE insulation is usually translucent and feels more slippery, while PVC is matte and denser.
Are XLPE cables used in residential buildings?
Yes, for risers and main switchboards. Mainly to increase current ratings and fire safety. Apartment wiring is traditionally done with PVC cables, but XLPE is also permissible.
What is the service life of a Pv power cable for 10 kV?
With proper current modes and laying conditions, at least 35 years. Periodic high‑voltage tests monitor the condition of the insulation.
What is a reduced‑flammability compound?
This is PVC compound with additives that reduce flame spread and smoke emission. It is marked as ng(A)-LS. Used for laying in residential and office buildings.
Conclusion
The choice between PVC and XLPE is determined by the requirements for heat resistance, fire safety and laying conditions. PVC insulation remains a cost‑effective and reliable solution for low‑voltage networks inside buildings. XLPE is indispensable in medium‑voltage trunk lines, at facilities with high current loads and in environments where low smoke and durability are important. Both types are available with copper conductors in the section with copper conductors and with aluminium conductors in the section with aluminium conductors. Accurate selection is based on GOST, the PUE and the manufacturer’s specifications.
