When we think about electricity, we usually imagine that environmental conditions have little importance. A 380 V motor is still a 380 V motor and a cable continues to conduct current the same way.
But when an electrical installation is located at 3,000, 4,000 or even more meters above sea level, the environment changes significantly.
In the Argentine Puna, where numerous large-scale mining projects exist, these conditions must be considered from the design stage. Lower atmospheric pressure, extreme temperatures, solar radiation, winds, dust and large distances between equipment can modify the operating conditions of an installation.
Electricity does not work with different laws at altitude. What changes are the conditions in which electrical equipment operates.
Less air, less cooling capacity
One of the first effects of altitude is related to something as everyday as air.
As altitude increases, atmospheric pressure and air density decrease. This means that a given volume of air contains less mass and therefore has less capacity to carry heat.
This is especially important in equipment that relies on air for cooling.
Electric motors, dry transformers, variable frequency drives, power supplies and other equipment may experience a temperature increase when operating at high altitude.
For this reason, many manufacturers set a reference altitude — frequently 1,000 meters above sea level — above which it is necessary to verify operating conditions and, in certain cases, apply a derating, that is, reduce the allowable capacity of the equipment.
For example, ABB notes that certain ventilated dry transformers require a reduction in their allowable power output above 1,000 meters due to the decrease in air density and cooling efficiency.
Something similar occurs with electric motors: the lower cooling capacity of the air may require a power reduction or a specific evaluation of the motor for the installation altitude. The IEC 60034-1 standard addresses the operating conditions and characteristics of rotating electrical machines.
Does electricity travel worse through cables?
No. Altitude does not make electric current "lose strength" simply by traveling through a cable.
The electrical resistance of a conductor depends mainly on its material, cross-section, length and temperature. The atmospheric pressure around the cable does not significantly change the resistance of copper or aluminum.
However, when we talk about industrial installations, the length of the cable run does matter, and a lot.
The greater the distance between both pieces of equipment, the longer the conductor will be and therefore the greater certain electrical effects will be:
- Voltage drop
- Energy losses
- Conductor heating
- Distributed capacitance of the cable
- Electromagnetic effects
- Phenomena associated with high-frequency pulses generated by the drive
VFD + motor: when distance starts to matter
A variable frequency drive does not deliver a conventional sinusoidal voltage identical to the grid to the motor. It uses power electronics to generate pulses that allow controlling the speed and torque of the motor.
When the cable between the drive and the motor is long, the electrical characteristics of the cable itself become more important. Voltage reflections, capacitive currents and electromagnetic compatibility issues can appear.
Drive manufacturers themselves establish installation conditions, limits and recommendations related to altitude, temperature and installation characteristics. For example, certain Rockwell Automation equipment specifies operating conditions without derating up to 1,000 meters and sets capacity reductions for higher altitudes.
Altitude also affects electrical insulation
Air works as an electrical insulator. But its ability to withstand a given electric field depends, among other factors, on its pressure and density.
At higher altitude there are fewer air molecules between two points. This can affect the behavior of electrical discharges and arcs, especially in higher-voltage installations.
IEC 60664-1 expressly addresses the correction of insulation distances for equipment installed at higher altitudes. Its current edition indicates that standard criteria apply up to 2,000 meters and provides guidance for installations located above that height.
For medium voltage, standards such as IEC 60071 and IEC 62271 also address insulation coordination and switchgear behavior under these conditions.
At 4,000 meters, the sun is also part of the problem
In the Puna, solar radiation and particularly ultraviolet radiation represents another environmental factor that must be taken into account.
UV radiation can degrade over time certain plastic materials and polymers used in:
- Cable covers
- Conduits
- Trays and accessories
- Boxes and cable glands
- Seals and insulators
- Fasteners and fixing elements
For this reason, it is important to use UV-rated cables or provide conduit protection for exposed installations.
Cable in open air or conduit?
The choice between running a cable in open air or inside conduit depends on the location and type of installation.
Conduit adds mechanical and environmental protection, but it also affects the thermal dissipation of the cable. The installation method is part of the calculation: a cable inside conduit cannot dissipate heat the same way as one in free air.
This means that the current-carrying capacity, voltage drop and operating temperature must be evaluated according to the actual installation method, not just the cable cross-section.
Designing for altitude is not just "doing the same, but bigger"
When designing a high-altitude installation, it is necessary to evaluate, among other aspects:
- Altitude → affects cooling and air insulation behavior
- Temperature → modifies cable current-carrying capacity and equipment operation
- Cable run length → influences voltage drop, losses and phenomena associated with motor cabling
- UV radiation → can accelerate the deterioration of materials exposed to the outdoors
- Dust and contamination → can affect equipment, ventilation and insulating surfaces
- Wind and mechanical conditions → must be considered in cable runs, trays and structures
- Lightning → requires evaluating the risk of strikes and defining protection measures
Engineering is also about knowing where an installation will operate
A motor may have the right power. A cable may have the right cross-section. A panel may have the right rated current. But if all those components were selected assuming sea-level conditions, the result can be very different when the same system must operate at more than 4,000 meters above sea level.
At PyP Electricidad we understand that every project has its own operating conditions. In high-altitude installations, knowing the environment is as important as knowing the installation.
PyP Electricidad — Connecting energy and quality.