Technical article
What suspension and tension assemblies are and why they are used
Definition of suspension and tension assemblies for transmission and substation lines, and what they include.
An assembly is a complete string of fittings and insulators —assembled and verified at the factory— that is installed as a single unit on a transmission or substation line, instead of being built piece by piece in the field. The two main types are the suspension assembly, which hangs the conductor from the tower or crossarm (the string works in bending, supporting the vertical weight of the cable), and the tension assembly or dead-end, which anchors and tensions the conductor at deflection, dead-end or crossing towers (the string works in traction). Partalum manufactures suspension, tension, “V”, dead-end and sectionalizing assemblies for 69–400 KV, in accordance with CFE specifications and class 52.5 insulator.
The advantage is direct: it is delivered as a complete assembly, not as loose parts, which reduces field assembly, the risk of installation error and construction time.
What does an assembly include?
A suspension or tension string combines, from tower to conductor:
- Structure-connection fitting — clevis, ball-eye, shackle or link.
- Insulators — disc string (class 52.5) or polymer insulator, depending on the voltage level and the environment.
- Yokes and spacers — when there are bundles of 2, 3 or 4 conductors per phase.
- Conductor clamp — suspension (holds) or compression dead-end/tension (anchors).
- Accessories — Stockbridge dampers against aeolian vibration and corona rings at high voltage levels.
Why are they used instead of loose parts?
| Advantage | What it solves |
|---|---|
| Factory assembly | Less work and installation error in the field |
| Per-assembly verification | Guaranteed mechanical compatibility between parts |
| Construction time | Installation as a single unit |
| Traceability | Each assembly is specified against standard and conductor |
The assembly is designed against the project specification: voltage level (KV), conductor type (ACSR, ACSS, AS or MCM copper), number of conductors per phase and applicable standard (CFE, NMX-ANCE). The mechanical strength of the string fittings is declared in the 80–480 KN range.
Suspension, tension and “V”: when each one?
- Suspension: towers on a straight span; the conductor passes through and the string hangs vertically.
- “V” suspension: controls the lateral swing of the conductor with two strings at an angle.
- Tension / dead-end: deflection towers, line dead-end or crossing; the conductor is anchored and tensioned.
- Sectionalizing: in the substation, to open or sectionalize spans.
Related reading
- Transmission line assemblies — suspension, tension and “V” for 1–4 conductors per phase.
- Substation assemblies — dead-end and sectionalizing, MCM copper.
- Difference between ACSR and ACSS conductors
FAQ
What engineering asks about this topic.
What is a suspension or tension assembly?
It is a complete string of fittings and insulators assembled and verified at the factory that is installed as a single unit on a transmission or substation line, instead of being built piece by piece in the field. The suspension assembly hangs the conductor (works in bending) and the tension or dead-end assembly anchors and tensions it (works in traction).
What does an assembly include?
From tower to conductor it combines: the structure-connection fitting (clevis, ball-eye, shackle or link), the insulators (class 52.5 disc string or polymer insulator), yokes and spacers when there are bundles of 2 to 4 conductors per phase, the conductor clamp (suspension or compression dead-end/tension) and accessories such as Stockbridge dampers and corona rings.
Why are they delivered as a unit and not as loose parts?
Because factory assembly reduces the work and the risk of installation error in the field, guarantees the mechanical compatibility between parts through per-assembly verification, shortens construction time by installing as a single unit, and provides traceability, since each assembly is specified against its standard and conductor.
What voltage levels and standards do Partalum assemblies cover?
Partalum manufactures suspension, tension, 'V', dead-end and sectionalizing assemblies for 69–400 KV, in accordance with CFE specifications and class 52.5 insulator. The mechanical strength of the string fittings is declared in the 80–480 KN range, and the assembly is designed against the voltage level, the conductor and the project standard.