During the hottest weeks of the summer, rising temperatures do not only affect people’s well-being or the operation of air-conditioning systems. Electrical infrastructure is also exposed to more demanding conditions.
Periods of intense heat may be accompanied by sudden power cuts, faults or localised service disruptions. The causes can vary and must be assessed on a case-by-case basis: network overloads, increased energy consumption, equipment malfunctions or the deterioration of individual components.
Heat can be an additional source of stress, particularly when high ambient temperatures are combined with heavy loads and conditions that limit heat dissipation.
Why do cables also generate heat?
When electric current flows through a cable, part of the electrical energy is converted into heat as a result of the Joule effect.
This is a normal phenomenon that is taken into account when electrical systems are designed. However, the heat generated must be able to dissipate into the surrounding environment, so that the conductor and insulating materials remain within their specified temperature limits.
A cable’s current-carrying capacity does not therefore depend solely on the cross-sectional area of the conductor, but also on several other factors:
- conductor material;
- type of insulation;
- installation method;
- number of cables installed together;
- ventilation;
- ambient temperature.
As the external temperature rises, heat dissipation can become more difficult.
High temperatures and cable current-carrying capacity
Current-carrying capacity values are established according to specific reference conditions.
When actual operating conditions differ from these standards, for example in environments with very high ambient temperatures, specific correction factors may need to be applied.
The issue does not only concern cables exposed directly to sunlight. High temperatures can also develop inside electrical panels, crowded cable ducts, poorly ventilated technical rooms, roof-mounted systems or photovoltaic installations.
Cable sizing must therefore always take actual operating conditions into account and should not be based exclusively on the product’s nominal ratings.
When heat is combined with increased energy consumption
During a heatwave, electricity demand often rises as well.
Air-conditioning units, cooling systems and refrigeration equipment may operate simultaneously and for prolonged periods.
Higher consumption can therefore place networks and electrical systems under greater loads at precisely the time when high temperatures make heat dissipation more difficult.
This does not mean that every summer power cut is caused by cables. Blackouts, faults and short circuits can have many different causes and always require a specific technical assessment.
High temperatures are, however, one of the conditions that must be considered when designing and managing electrical systems.
What can happen under unsuitable operating conditions?
When a cable operates for prolonged periods outside its specified conditions, the resulting increase in temperature can accelerate the deterioration of its materials.
Over time, this may lead to:
- faster ageing of the insulation;
- a shorter service life for the connection;
- loss of the mechanical properties of cable sheaths;
- a greater likelihood of faults or protective devices being triggered.
Loose connections, incorrectly tightened terminals or deteriorated contact points can also generate high temperatures in localised areas.
The behaviour of the system therefore depends on all its components, not only on the individual cable.
Not all cables are designed for the same temperatures
Different insulating and sheathing materials offer different thermal properties.
PVC, cross-linked polyethylene, rubber, polyurethane and silicone are selected according to the operating conditions expected for each application.
The choice of cable must therefore take several factors into account:
- ambient temperature;
- maximum conductor temperature;
- installation method;
- operating conditions of the system.
It is not enough to consider only the cable’s cross-sectional area or rated voltage.
Design and prevention
Extreme temperatures make it increasingly important to assess electrical systems under the most demanding environmental conditions.
Correct design must consider not only average operation throughout the year, but also periods of very high temperatures, peak consumption, continuous operation and reduced ventilation.
High temperatures are not the only aspect that should be checked during the summer. A slowdown or temporary suspension of production activities can provide a useful opportunity to inspect electrical connections and carry out any necessary work before operations resume.
In a previous article, we discussed summer maintenance of electrical systems and the importance of checking cables as well, examining the main inspections that can help prevent faults and unexpected downtime.
Choosing a cable by considering the entire system
A cable never operates in isolation.
Temperature, current, installation method, the presence of other connections and ventilation all contribute to its behaviour over time.
For this reason, cable selection must begin with a complete assessment of the application.
SADA CAVI offers a wide range of solutions for industry, automation, energy and specialist applications, supporting customers in selecting the most suitable products for different operating conditions.
