Introduction: Hardware – The Vital Links in the Distribution Chain
An old engineering proverb says: “A chain is only as strong as its weakest link.” In overhead power distribution networks using Aerial Bundled Cable (ABC), this proverb holds truer than anywhere else.
You can buy the best, highest-quality self-supporting cable (e.g., from a reputable brand like Sim Rad Sama), but if you make mistakes in selecting and installing the hardware and connectors, you jeopardize the entire project investment. Inappropriate hardware or incorrect installation leads not only to frequent power outages and customer dissatisfaction but can also cause dangerous incidents such as cable breakage, pole failure, and even fire.
In the world of self-supporting cables, there is a wide variety of hardware: tension clamps, suspension clamps, serrated connectors, jumpers, etc. For a novice contractor or supervising engineer, figuring out exactly which component is suitable for which position on the pole can be confusing.
In this comprehensive guide, our technical and engineering unit at Sim Rad Sama aims to cut through the complexity and examine the role of each component in simple, practical language. The goal is that after reading this article, by looking at an overhead single-line diagram, you will know exactly which hardware you need on each pole.
Fundamental Principle: Who Bears the Mechanical Load? (The Messenger Rule)
Before we introduce the clamps, you must understand the most important principle of self-supporting cable networks.
In an ABC system, the entire weight of the cable and all tensile forces from wind, ice, and temperature changes must be borne only by a specific wire. This wire is called the “messenger wire” or simply “messenger.”
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In low-voltage cables (e.g., 6-core), the neutral wire usually also acts as the messenger (made of high-strength aluminum alloy).
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In medium-voltage cables, a separate steel or alloy wire serves as the messenger.
Golden Rule of Installation: All mechanical hardware (tension and suspension clamps) must grip only the messenger wire. Phase and lighting conductors must never be placed under mechanical tension, as they will quickly be damaged and break.
With this principle understood, let’s move on to the classification of hardware.
Section 1: Dead-End & Anchor Fittings
These are the “anchors” of the network. Wherever the cable needs to be completely fixed and withstand high tensile forces, these fittings are used.
1. Dead-End / Tension Clamp
Where is it used?
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Start and end poles: Where the line begins or ends.
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Sharp angle poles: When the line changes direction significantly (usually more than 30 or 45 degrees, depending on design). On such poles, one clamp anchors the cable from one side, and another clamp directs the cable to the next span (these are sometimes called double‑tension poles).
How does it work? (Wedge mechanism)
Most modern self‑supporting cable clamps use a wedge mechanism. The messenger wire sits between two wedge‑shaped jaws. The greater the cable tension, the more the wedges are driven together and the tighter they grip the wire. This clever design makes the clamp more resistant to increased tension (e.g., in winter cold).
Important installation tips:
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Ensure the clamp size matches the messenger wire size of your cable.
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The clamp must grip only the messenger. Be careful not to pinch the phase insulation between the clamp jaws.
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The flexible steel wire (bail) connecting the clamp to the pole hook must be intact and free of corrosion.
Section 2: Suspension Fittings
These are the “cradles” of the network. Their job is only to bear the vertical weight of the cable, not horizontal tension.
2. Suspension Clamp
Where is it used?
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Intermediate poles: On poles that are on a straight path (or with a very small deviation angle, e.g., below 30°). On these poles, the cable is not cut and simply passes over the pole.
How does it work?
The suspension clamp acts like a pulley or a cradle. The messenger wire rests inside it, and the bolt is tightened.
Critical point (difference from tension clamp): A suspension clamp must not “bite into” or completely lock the messenger wire. The wire should be able to slide slightly and have longitudinal movement inside the clamp.
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Why? If a sudden extra load occurs in a span (e.g., a tree falls on the cable or a vehicle hits the previous pole) and the cable is locked in the suspension clamp, all the force is transferred to the intermediate pole and may break it. But if the cable can slide, the force is distributed among several poles, preventing pole breakage.
Section 3: Electrical Connection & Tapping Fittings
So far we have installed the cable mechanically. Now it’s time to establish the electrical current. In ABC systems, there is no need to strip the insulation!
3. Insulation Piercing Connectors (IPCs)
These are the “miracle” of ABC networks. IPCs have dramatically increased installation speed and safety.
Where are they used?
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Anywhere a tap needs to be taken from the main cable (e.g., connecting a service cable to the main network).
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Connecting jumpers between two main cables at tension poles.
How do they work? (Serrated technology)
These connectors have sharp metal teeth on both sides, coated with special waterproof grease. When you place the two cables (main and tap) inside and tighten the bolt, the teeth pierce the cable insulation, contact the aluminum conductor underneath, and make the electrical connection.
Critical point: Shear‑head nuts
The biggest mistake installers make is over‑tightening or under‑tightening IPCs.
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Under‑tightened: Loose connection → overheating → connector melting.
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Over‑tightened: Damage to the conductor → strand breakage.
To solve this, standard IPCs have shear‑head bolts. You start tightening with a wrench. When the torque reaches the factory‑set standard value, the bolt head shears off. That means a complete, standard connection. Never try to tighten the remaining stub with another wrench after the head has sheared off!
4. Jumper Clamp or Connection Clamp
Where is it used?
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On sharp‑angle or dead‑end poles where the main cable is cut using tension clamps, these clamps are used to reconnect the messenger wire (neutral) electrically from one side of the pole to the other.
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Note: For connecting the phases at these points, IPCs are usually used, but for the messenger (if it is bare), special jumper clamps (parallel groove clamps / PG clamps) are used.
Section 4: Quick Selection Guide – Hardware at a Glance
For a quick summary, this table helps you decide at a glance.
| Type of Pole / Position | Cable Condition at this Point | Mechanical Hardware Required | Electrical Hardware Required |
|---|---|---|---|
| Start / End Pole (Dead‑End) | Cable begins or ends. Full tension, one direction. | 1 dead‑end (tension) clamp + wall or pole bracket | If needed for grounding or transformer connection |
| Intermediate / Tangent Pole | Cable passes through. Deviation angle < 30° | 1 suspension clamp + hook or eyebolt | Usually none (unless tapping a service) |
| Sharp Angle Pole | Cable changes direction sharply. Angle > 30° | 2 dead‑end (tension) clamps (one for entry, one for exit) | IPCs and jumper for reconnecting phases and neutral |
| Service Drop (Customer Connection) | Connecting service cable to main network | – | IPCs (number depending on service phases) |
Conclusion: Don’t Sacrifice Quality for Price
Self‑supporting cable hardware may be a small part of the network by weight and volume, but it is the most important part for safety and performance. Using non‑standard hardware – with poor alloy, not resistant to UV radiation, or lacking proper engineering design – will sooner or later impose heavy repair costs and outages.
When purchasing self‑supporting cable from Sim Rad Sama, be sure to consult our technical experts about selecting standard hardware compatible with our products, so that you can provide a reliable and durable package for your distribution network. A stable network results from the combination of quality cable and standard hardware.
[📞 Contact Sim Rad Sama Technical Sales & Consulting for overhead network equipment inquiries]