Introduction: Two Links of One Chain
When electrifying a private house or a country cottage, a reasonable question arises: which wire should be used to run the line from the pole to the service entrance panel, and which one to distribute the network inside? SIP is a self-supporting insulated wire for overhead mains, while VVG is a power cable with PVC insulation for fixed installation indoors and in the ground. They cannot be called competitors in the strict sense: each is created for its own section, but at the boundary of the plot they meet, and an error in connection or the wrong choice of material at any stage nullifies the entire reliability of the scheme.
SIP replaced bare aluminium wires, eliminating short circuits during clashing and reducing losses. VVG has served for decades as the basis of distribution networks inside buildings. Comparing them on the principle of “which is better” is pointless — it is more correct to understand at which point of the plot boundary the overhead line ends and the indoor wiring begins, and what requirements are imposed on each section. That is what this article is about. Basic information about the self-supporting wire is gathered in the review details about SIP, and about the indoor cable — in the section VVG cable.
Comparative Table of SIP and VVG
| Parameter | SIP (SIP-4, SIP-2) | VVG (VVGng, VVGng-LS) |
| Main purpose | Overhead lines 0.4–1 kV, service drops to a house | Fixed wiring inside buildings, in the ground in a protective pipe |
| Conductor design | Aluminium, stranded, insulated with light-stabilised polyethylene | Copper or aluminium, solid or stranded, with PVC insulation and an overall sheath |
| Voltage | 0.6/1 kV | 0.66 or 1 kV according to GOST 31996 |
| Cross-section | 16–120 mm² | 1.5–240 mm² |
| Load-bearing capacity | Built-in steel core (in SIP-2) or reinforced neutral conductor (SIP-4) | Not provided, the cable is not self-supporting |
| Bending radius | Not less than 10 diameters | 7.5–10 diameters depending on the cross-section |
| Resistance to UV and precipitation | High, polyethylene with carbon black filling | Low, PVC degrades in the sun |
| Fire safety | Combustible, not intended for indoors | ng, ng-LS, ng-FRLS — a wide spectrum |
| Service life | Not less than 25 years outdoors | 25–30 years indoors |
| Installation | Requires tensioning on poles, anchor clamps, special equipment | Laying in grooves, ducts, trays, pipes |
| Cost (per metre) | Lower due to aluminium | Higher for copper, comparable for aluminium versions |
Design and Purpose: Why They Are Different
SIP is insulated aluminium conductors twisted around a steel core, or a self-supporting construction with a neutral conductor that bears the mechanical load. The insulation of cross-linked or thermoplastic polyethylene with the addition of carbon black is not afraid of ultraviolet radiation, rain and snow. The wire is designed for decades under the open sky. Its task is to deliver electricity from the main to the service entrance panel with minimal losses and without the risk of a short circuit between phases.
VVG is a classic cable for indoors. Its sheath of PVC compound provides flexibility and fire safety, but degrades under the sun. Copper conductors give low resistance and compactness, while aluminium versions AVVG reduce the price at large cross-sections. It is VVG that runs from the incoming circuit breaker around the house, floors and rooms. More about the difference between VVGng and VVGng-LS versions can be found in the comparison VVGng or VVGng-LS.
Installation, Transition and Connection
SIP is installed using anchor brackets, tension clamps and piercing branch connectors. No additional support is required — the wire carries itself between the poles. At the building entry, it is fixed to the facade and led into the distribution panel through a sealed entry. VVG indoors is laid in grooves, pipes, cable ducts or openly on walls in places where there are no mechanical risks.
The critical junction is the transition from SIP to VVG. An aluminium conductor must not be directly connected to a copper terminal without a bimetallic washer or lug, otherwise a galvanic couple forms, the contact oxidises and heats up. Usually, a circuit breaker is installed in the panel, to the upper terminals of which the SIP comes, and from the lower ones the VVG leaves. The connection must be made using an anti-oxidation compound and tightened with a regulated torque. Practical techniques for tensioning and fixing the wire on poles are disclosed in the guide SIP laying and installation.
Cost, Losses and Service Life
Per linear metre, SIP is noticeably cheaper than copper VVG: aluminium plus the absence of an expensive sheath. For an overhead service drop 30 metres long, the price difference between SIP 4×16 and copper VVG 4×10 amounts to several thousand roubles. At the same time, the voltage drop on an aluminium wire is higher than on a copper one of the same cross-section, but in practice for 15 kW and a length of 30 metres the drop does not exceed 3–5%, which fits within the PUE standards. The calculation of losses is performed according to standard formulas, based on the load current and the conductor cross-section.
The service life of SIP outdoors is at least 25 years; VVG indoors — 30 years and more. Aluminium versions of VVG are also durable, but require careful tightening of contacts due to the creep of the metal. A copper conductor is more stable in this respect. The choice of cross-section for a load of 15 kW for a three-phase network gives: for SIP, 16 mm² is sufficient, for copper VVG — 10 mm², for aluminium AVVG — 16 mm². The exact current tables are given in the PUE and the factory passports. A certificate of conformity for any batch can be obtained from the manufacturer; VVG is produced according to GOST 31996.
When to Choose SIP
- Overhead service drop from a pole to a house, distance from 10 to 50 metres. SIP does not require a messenger wire and is installed faster.
- Mains on poles inside a settlement or a garden community. The wire is self-supporting, saving on fastening structures.
- Temporary lines on construction sites with suspension. It is quickly rolled out and dismantled.
- Where resistance to weather conditions is important: snow, wind, rain. The insulation eliminates clashing.
- Facilities with a limited budget, where aluminium wins in cost.
When to Choose VVG
- Internal wiring in the house: from the panel to sockets, lighting, boiler. Fire safety according to SP 256.
- Laying in the ground in a protective HDPE pipe. For direct burial, armoured VBbShv is needed, but VVG in a pipe is also permissible.
- Premises with increased requirements for smoke and combustion: VVGng-LS is mandatory.
- Networks where copper is needed to minimise losses on long indoor routes or to power sensitive equipment.
- Any fixed routes inside buildings, including concrete, plasterboard, cable ducts.
Typical Mistakes in Selection and Installation
- Direct connection of aluminium SIP with copper VVG without a bimetallic lug or compound. The contact oxidises and heats up, a fire is possible.
- Laying VVG overhead instead of SIP. The sheath without UV protection will crack after 1–2 seasons, the cable will fail.
- Using SIP indoors. The wire does not comply with fire standards, is combustible, and gives off corrosive smoke.
- Underestimating the cross-section at the service entrance: for 15 kW on three phases, SIP must be at least 16 mm², otherwise the losses will exceed the permissible 5%.
- Ignoring the bending radius: when installing SIP, a sharp turn at the facade without a loop reserve leads to deformation of the insulation and a reduction in service life.
- Tightening contacts without a torque wrench: aluminium conductors are subject to creep, a loose contact heats up, an over-tightened one deforms.
Frequently Asked Questions
What is the difference between SIP and VVG?
SIP is a self-supporting outdoor wire with polyethylene insulation, VVG is a cable for indoors with PVC insulation. The first is for overhead, the second for walls and ground.
Can VVG be used for a service drop from a pole to a house?
Overhead — absolutely not: UV will destroy the sheath. In the ground in an HDPE pipe — it is permissible, but labour-intensive and more expensive than SIP overhead.
How to correctly connect SIP and VVG?
Via a circuit breaker in the service entrance panel. The aluminium conductor of the SIP is connected to the upper terminals with bimetallic compound, the copper VVG — to the lower ones. Twisting or direct crimping is not allowed.
Which cable can withstand a load of 15 kW?
For a three-phase network: copper VVG — with a cross-section of 10 mm², aluminium AVVG or SIP — 16 mm². With a single-phase service drop, the cross-sections are significantly higher, which is rarely practised.
What are SIP-4 and SIP-2?
SIP-4 — without a steel core, with a reinforced neutral conductor. SIP-2 — with a steel core inside the neutral conductor, for trunk lines with large spans.
Is a certificate required for SIP and VVG?
Yes, both types must have a certificate of conformity: VVG — according to GOST 31996, SIP — according to GOST 31946-2012. The passport for the coil contains the actual conductor diameters, outer diameter and weight.
Conclusion
SIP and VVG are not rivals, but successive stages of one power supply system. SIP is indispensable for an overhead service drop, where self-supporting capability and weather resistance are needed. VVG is the standard for indoor wiring and laying in the ground under protection. Their competent connection through a service entrance panel with observance of material compatibility rules guarantees the safe and long-term operation of the entire line. When selecting the cross-section and the type, one proceeds from the load, distance and environmental conditions — this is the only way to obtain reliable electricity in the house.
