Oct 31, 2025

How to Choose and Install Medium Voltage Covered Cable (ABNT NBR 11873): The Complete Guide

If you’ve ever worked on an overhead power line in summer heat or under drizzle, you already know one thing — the cable has withstood many environmental influences. Sun, rain, wind, dust, even birds — these are all factors that have an impact. That’s why choosing the right cable isn’t just a paperwork decision; it’s related to the security of the system.
One choice that keeps coming up in medium-voltage projects is Covered Cable (ABNT NBR 11873). Sounds technical? It simply refers to a type of aerial insulated cable widely used across Brazil and many other regions for 15 kV to 35kV lines. Let’s explain what it is, how it’s different from the usual PVC stuff, and security applications in different scenes.

What Is Medium Voltage Covered Cable (ABNT NBR 11873)?

Medium Voltage Covered Cable (ABNT NBR 11873) isn’t some new product — it’s an overhead aluminum conductor with a protective insulation, with good electrical performance and weather resistance.
NBR is short for Norma Brasileira, Brazil’s national standard from ABNT, the country’s technical association.
According to TDDL, the structure of Medium Voltage Covered Cable is:
Structure type 1:

Conductor: Stranded and compacted aluminum.
Inner layer: A semi-conductive black screen that smooths out electric stress(if required).
Inner Insulation: PE or XLPE, usually in natural.
Outer Insulation: UV-resistant and Anti-tracking PE or XLPE, usually in black or gray.

Structure type 2:

Conductor: Stranded and compacted aluminum.
Inner layer: A semi-conductive black screen that smooths out electric stress (if required).
Insulation: UV-resistant and Anti-tracking PE or XLPE, usually in black.
Operating temperature: 75 °C for PE or 90 °C for XLPE.
Voltage classes: 15 kV, 25 kV, and 35 kV.

These cables are common in aerial systems, where several phases hang close together yet stay separated by insulation. You’ll see them in rural area, coastal towns, and areas with densely trees or with high rainfall.

Medium Voltage Covered Cable vs. Normal PVC Cable

People sometimes ask, “Can’t I just use PVC cable up there?” Well, you can, if you enjoy early maintenance calls. Let’s see why that’s not the best idea.

1. Structures and Materials

Medium Voltage Covered Cables have double layers covered — a conductive inner layer plus an XLPE or PE insulation. And even with triple layers covered layers — a conductive inner layer plus double XLPE or PE insulation. That means they can handle medium voltage and still work well even in rain and sunlight.
PVC cables? Only with one simple insulation layer. They are usually used in low-voltage system, the electrical performance and long-term operating temperature are not as good as XLPE, the abrasion resistant is less than PE and does not have anti-tracking.

2. Installation scene:

Medium Voltage Covered Cable (ABNT NBR 11873): Made for overhead system. Hang it on poles, run it through spacers.
Normal PVC Cable:Low-voltage PVC cables suitable for indoor or underground installations, up to 3.6/6kV power cables, and also applicable to outdoor low-voltage overhead systems.

3. Voltage and Reliability

Medium Voltage Covered Cables carry medium voltage — 15 to 35 kV — without sparking between phases.
Normal PVC Cables usually used for 0.6/1kV, select appropriate materials based on the application scenario and voltage level.

4. Longevity

Compared to PE and XLPE insulation, PVC is more absorbent and has weaker aging resistance. PE and XLPE are often used in overhead systems.

Step-by-Step: Installing Medium Voltage Covered Cable (ABNT NBR 11873)

Even experienced linemen agree — overhead work is part technique, part patience. Here’s a simplified walk-through based on field habits, not just theory.

1. Make It Safe First

Kill the power, tag it, and test it. Never trust that “it’s probably off.” A medium-voltage surprise isn’t something anyone forgets.

2. Pick the Right Size

Record the product's model, specifications, outer diameter, and weight. For example:

15 kV: 35 mm² conductor, about 13 mm diameter, 185 kg/km.
25 kV: 35 mm², 16.2 mm diameter, 260 kg/km.
35 kV: 70 mm², 26.5 mm diameter, 653 kg/km.

Get this wrong and you’ll either waste money or risk overheating. Many engineers carry a small notebook listing the weight and breaking load — old habit, but it saves rework.

3. Prepare the Hardware

Insulators, spacers, brackets — all must fit the cable’s size and weight. Make sure the material of the spacer matches the dielectric strength of the jacket. A mismatch may lead to tracking during wet weather.

4. Stringing the Cable

Feed the reel slowly. Use pulleys or rollers; don’t drag it over metal. Check sag and tension with a simple dynamometer or by sight if you’ve been doing this long enough. Slight sag is normal — too tight, and it snaps in winter; too loose, and it slaps in the wind.

5. Termination

Trim carefully — only remove what’s needed: outer jacket, inner insulation, and the semi-conductive layer. Use connectors meant for aluminum, not copper lugs borrowed from another job. Finish with a heat-shrink sleeve to seal against moisture.

6. Testing and Energizing

Before flipping the switch back on, do a quick insulation-resistance test. Walk the line, check for scratches or cracked insulation. Clear branches, adjust tension, then energize slowly. Most crews stand back a few meters the first minute — just in case.

Conclusion & Safety Notes

Installing Medium Voltage Covered Cable (ABNT NBR 11873) isn’t rocket science. Still, it rewards good habits — double-checking clearances, cleaning connectors, re-tightening anchors after a temperature swing.
Think of it as preventive medicine for your power grid: small effort upfront, big payoff later.
A few reminders worth repeating:

Always lock out and test before touching.
Handle the XLPE insulation gently — one nick can become a flash point months later.
Match every connector and spacer to the cable’s voltage class.
Re-inspect after storms or seasonal shifts. Aluminum expands more than you’d guess.

Done right, a covered line can stay up for 30 years or more with barely a service call — and that’s a record any maintenance team likes to brag about.

FAQ

Q: What is Covered Cable (ABNT NBR 11873) used for?

A: Covered Cable (ABNT NBR 11873) is built for medium-voltage overhead lines — anywhere from 15 kV to 35 kV. Utilities use it for both Intercity connecting lines and long rural stretches where insulation and weather protection make maintenance easier and safer.

Q: Does Covered Cable (ABNT NBR 11873) mean the same as a regular insulated cable?

A: Not really. Regular insulated cable only with one simple insulation layer. They are usually used in low-voltage system, the electrical performance and long-term operating temperature are not as good as XLPE, the abrasion resistant is less than PE and does not have anti-tracking.

Q: Can Medium Voltage Covered Cable (ABNT NBR 11873) be used underground or indoors?

A: Nope. It’s meant to hang in the open air, supported by poles or spacers.
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