Why does the SIP-16 connection require a special approach?

Self-supporting insulated wire SIP-16 is widely used for overhead power lines up to 1 kV, but its connection is a task where errors can lead to contact overheating, line break or even fire. Unlike traditional cables, SIP has aluminum cores with polyethylene insulation that cannot simply be twisted or soldered. Incorrect splicing is fraught increase in contact resistance by 5–10 times, which is critical for networks with high loads.

The main problem is aluminum oxidation in the air, which worsens contact. Even a micron layer of oxide increases resistance, and at current loads up to 100 A (typical for SIP-16) this leads to local overheating. The second nuance is mechanical strength: the connector must withstand tensile loads up to 300–400 kgf, otherwise the wire will break due to icing or wind. Therefore, specialized clamps are used for splicing, and not β€œold-fashioned” twists.

In this article we will analyze all allowed connection methods (according to PUE 7.4.35 and GOST R 52373-2005), we will dwell on the tools in detail, and also show how to avoid typical mistakes that even experienced electricians make.

πŸ“Š Which SIP connection method do you use most often?
Piercing clamps
Bolt connectors
Nuts (branch squeezes)
Sleeves for crimping

Acceptable methods of connecting SIP-16 according to PUE standards

Electrical Installation Rules (ELI) strictly regulate methods for connecting self-supporting wires. For SIP-16 (section 16 mmΒ²) are only permitted four types of connectors, each of which has its own advantages and limitations:

  • πŸ”Ή Piercing clamps (for example, Niled P616R or Ensto SIC 16) - do not require stripping of insulation, are sealed, but disposable.
  • πŸ”Ή Bolt connectors (type SO 155-16) - reusable, can withstand high currents, but stripping of the core is required.
  • πŸ”Ή Branch squeezes (β€œnuts”) - suitable for temporary connections or branches, but not for the main line.
  • πŸ”Ή Sleeves for crimping (for example, GIL 16) - the most reliable solution for permanent connections, but require press jaws.

Important: twisting, soldering and welding for SIPs are prohibited! Aluminum loses strength when heated, and insulation melts at 120Β°C. Even if the twist β€œholds” mechanically, after 1–2 years oxidation will make it a source of problems.

Connector type Max. current (A) Cleaning required Reusable Price per unit (rub.)
Piercing clamp 100 No No 120–250
Bolt connector 120 Yes Yes 80–150
Branch compression 80 Yes Yes 50–100
Sleeve for crimping 130 Yes No 60–120
⚠️ Attention: When using bolted connectors necessarily apply alum paste (for example, Quartzgel) onto the cores - this prevents oxidation and reduces the contact resistance by 30–40%.

Step-by-step instructions: connecting SIP-16 with a piercing clamp

This method is the fastest and does not require stripping the insulation, so it is often used to repair live lines (up to 1 kV). Let's look at the process using a clamp as an example Niled P616R:

Make sure the voltage is off (check with the indicator!)

Clean the wire from dirt and ice (use a brush with plastic bristles)

Mark the connection point (step back 30–50 cm from the support)

Prepare tools: torque wrench, SIP knife, dielectric gloves -->

Step 1. Place the clamp on the wire so that piercing contacts were directed towards the vein. Don't mix up the sides - there is usually an "IN" mark on the case.

Step 2. Tighten the bolt firmly with a torque wrench 12–15 Nm. Falling short will lead to poor contact, and tug-of-war - to damage to the core. The clamp contacts must pass through the insulation and rest against the aluminum.

Step 3. After tightening, check tightness: There should be no cracks on the housing, and no insulation should protrude from under the gaskets. If the clamp is damaged, replace it without trying to β€œtighten” it.

Step 4. For reliability, close the connection point heat-shrinkable tube (for example, 3M Scotchcast) or a special cap. This will protect against moisture and UV radiation.

πŸ’‘

If connecting wires in the rain, use silicone grease (for example, NYE Lubricants 345A) on the bolt thread - this will prevent corrosion and facilitate future dismantling.

Bolted connectors: when and how to use them

Bolt clamps (eg SO 155-16 or KWT SO-16) is a universal solution for permanent connectionswhere high current load is required. Their advantage is that, if necessary, the connector can be disassembled and reused. However, there are also disadvantages:

  • πŸ”§ Required stripping insulation by 30–40 mm (use a CIP knife with a depth limiter!).
  • πŸ”§ Necessary degrease conductors with alcohol and apply alum paste.
  • πŸ”§ The tightening of the bolts should be uniform (use a torque wrench).

Step-by-step algorithm:

  1. Strip the insulation from both wires on 35–40 mmwithout damaging the aluminum (use knife with hook for SIP).
  2. Clean the veins wire brush and apply alum paste thin layer.
  3. Insert the wires into the connector so that they overlapped by at least 20 mm.
  4. Tighten the bolts crosswise firmly 8–10 Nm (for SO 155-16).
  5. Check micrometer or calipers, that the thickness of the pressed connection does not exceed 18–20 mm.
  6. Cover the connection heat-shrinkable sleeve (for example, 3M 5605).
⚠️ Attention: If after tightening the bolts the wires moved more than 2 mm inside the connector - the connection is defective! Take it apart and start again, otherwise the contact will burn out in a year.
What happens if you don’t use alum paste?

Without paste, aluminum oxidizes in 3–6 months, the contact resistance grows by 5–7 times, which leads to local overheating up to 150–200Β°C. At best, the line breaks; at worst, the insulation catches fire. The paste creates a protective film and reduces resistance by 30–40%.

Crimping with sleeves: the most reliable, but complex solution

Sleeves (for example, GIL 16 or KWT G-16) provide minimum contact resistance and withstand currents up to 130 A, but require special tool β€” hydraulic press jaws (for example, KWT HK-25). This method is recommended for trunk lines or areas with high loads.

What you will need:

  • πŸ”¨ Sleeve GIL 16 (aluminum, with an internal diameter of 4.5 mm).
  • πŸ”¨ Press pliers with a hexagonal matrix for a cross section of 16 mmΒ².
  • πŸ”¨ SIP knife, metal brush, alum paste.
  • πŸ”¨ Heat-shrinkable tube Ø 25–30 mm.

Critical points:

  1. Strip the wires 40–45 mm (sleeve length plus 5 mm).
  2. Lubricate the wires with paste and insert into the sleeve all the way β€” a gap of more than 1 mm is unacceptable!
  3. Do two crimps along the edges of the sleeve (the distance between them is 10–15 mm).
  4. Check micrometer, that the thickness of the crimp at the crimping point 16.5–17.5 mm.

A mistake many installers make - single crimp in the middle of the sleeve. This leads to uneven contact and the risk of the core β€œslipping out” under load. Always crimp twice around the edges!

πŸ’‘

Crimping with sleeves is the only method that guarantees 100% mechanical strength connections (withstands loads up to 400 kgf).

Common mistakes and how to avoid them

Even experienced electricians sometimes make mistakes when splicing. SIP-16. Here TOP-5 most dangerous:

  1. Using twists or soldering β€” after 6–12 months, such a connection will begin to heat up and melt the insulation. SIP You can only crimp or bolt!
  2. Insufficient bolt tightening - leads to microarc discharge at the point of contact, which destroys the aluminum. Always use a torque wrench.
  3. Lack of sealing β€” moisture penetrates under the insulation, causing corrosion. Even in dry climates this will eventually lead to breakage.
  4. Damage to the load-bearing core when stripping - if you cut it deeper than 0.3 mm, the wire will lose up to 20% of its strength.
  5. Using off-section connectors - for example, clamp for 25 mmΒ² on SIP-16. This leads to bad contact and overheating.

Another common problem is wrong choice of connection point. Cannot be spliced SIP:

  • 🚫 In the flight between the supports (only on the support or 1 m from it!).
  • 🚫 In areas with a wire bend (minimum bend radius is 10 cable diameters).
  • 🚫 Under trees or in places where mechanical damage is possible.

How to check connection quality

Even if the connection looks reliable visually, it needs to be check before commissioning. Here 3 required tests:

  1. Visual inspection:
    • πŸ” There are no cracks on the connector body.
    • πŸ” The insulation is not damaged (no cuts deeper than 0.5 mm).
    • πŸ” The bolts are tightened evenly, without distortions.
  2. Checking contact resistance:
    • πŸ“Š Use microohmmeter (for example, Fluke 1623).
    • πŸ“Š Resistance should be no more 0.0003 Ohm (for a new connection).
    • πŸ“Š If the value is higher 0.0005 Ohm - redo the connection!
  • Mechanical test:
    • πŸ’ͺ Pull the wire firmly 50–100 kgf (use a dynamometer).
    • πŸ’ͺ The connection should not move or deform.

    For long lines (more than 100 m) it is also recommended to carry out thermographic control 1–2 hours after applying the load. Use thermal imager (for example, FLIR E4) - the connection temperature should not exceed the wire temperature by more than 10Β°C.

    ⚠️ Attention: If, when checking with a microohmmeter, the resistance β€œfloats” (changes with repeated measurements), this is a sign unstable contact. A common cause is an oxidized core or a weak tightening.

    FAQ: Frequently asked questions about splicing SIP-16

    Is it possible to connect SIP-16 with copper wire?

    No! Direct connection of aluminum to copper prohibited (PUE 2.1.48) due to electrochemical corrosion. Use bimetallic adapter sleeves (for example, GAM 16) or bolt connectors with spacer washer.

    What is the service life of a SIP connection?

    When installed correctly:

    • πŸ”Ή Piercing clamps - 10–15 years (disposable, but sealed).
    • πŸ”Ή Bolt connectors - 15–20 years (can be served).
    • πŸ”ΉCrimping with sleeves - 25+ years (the most durable solution).
    What to do if the SIP breaks in the span?

    If a break occurs not supported, you need:

    1. Install intermediate support or tension clamp.
    2. Use repair coupling (for example, Ensto SICM 16).
    3. Strengthen the connection two piercing clamps on both sides.

    ❌ You can't Simply splicing a wire in a span without support will lead to sagging and breakage under load.

    How to protect a connection from birds?

    Birds often peck at SIP insulation, especially if it is shiny. Solutions:

    • 🐦 Use protective caps (for example, KWT CAP-16).
    • 🐦 Apply to insulation matte protective spray (for example, 3M Scotchkote).
    • 🐦 Install repellers (for example, Bird-X) on supports.
    Is it possible to splice SIPs in the rain?

    Technically you can, but with mandatory measures:

    • β˜” Use sealed clamps (for example, Niled P616R with silicone seal).
    • β˜” Apply dielectric grease on bolts (for example, NYE Lubricants 345A).
    • β˜” After installation, check the connection megohmmeter (insulation resistance must be > 10 MΞ©).

    ⚠️ Important: If it goes heavy rain or temperature is lower –10Β°C, it is better to postpone installation - the insulation becomes fragile.