Keeping Transformers Safe in High Ambient Temperatures

what is ambient temperature

Ambient temperature refers to the temperature of the surrounding environment where an object or system is located. It’s the temperature of the air or other substances that are in contact with the object or system.

Ambient temperature can have a significant impact on the performance and safety of various electrical and mechanical systems, including transformers.

As ambient temperature increases, it can cause the temperature of the system to rise, which can lead to reduced efficiency and even damage in some cases. Therefore, it’s essential to understand the effects of ambient temperature on different systems and take appropriate measures to maintain safe and efficient operation.

Effects of Ambient Temperature on Transformers

Transformers are crucial components of power systems that facilitate the transmission of electrical energy from one circuit to another.

However, the performance of transformers can be affected by ambient temperature, which is the temperature of the air or environment in which they operate.

Here, we will examine the effects of ambient temperature on transformers.

Temperature Rise

The temperature of transformers increases when they are in operation, and ambient temperature can impact the rate of temperature rise.

For instance, when the ambient temperature is high, the cooling capacity of the transformer decreases, causing the transformer’s temperature to rise more rapidly.

Similarly, when the ambient temperature is low, the cooling capacity increases, causing the temperature to rise at a slower rate.

Insulation Aging

The insulation materials used in transformers can also be affected by ambient temperature. High temperatures can accelerate the aging process of insulation, leading to a decrease in its dielectric strength. This, in turn, can cause the transformer to fail, leading to costly repairs and downtime.

Load Capacity

Transformers are designed to operate under specific temperature ranges. When the ambient temperature exceeds this range, the transformer’s load capacity can decrease, which means it can deliver less electrical energy than it’s rated for.

This can cause voltage drops and power outages, which can have severe consequences in critical applications.

Oil Viscosity

The oil used in transformers acts as a coolant and insulator. However, the viscosity of the oil is dependent on ambient temperature.

When the temperature is high, the oil viscosity decreases, reducing its effectiveness as a coolant. This can cause the transformer to overheat and fail.


High humidity levels and high temperatures can cause corrosion on the transformer’s metal parts, which can lead to insulation failure and reduced transformer lifespan.

How to Protect Transformers from Overheating during High Ambient Temperatures?

Cooling Systems

Cooling systems are crucial to ensure that transformers remain within their temperature limits. Air or liquid cooling systems can be used to regulate the temperature of transformers.

Air cooling systems use fans to blow air over the transformer’s surface to dissipate heat, while liquid cooling systems circulate coolant through the transformer’s windings to absorb and dissipate heat.

Oil Analysis

Regular oil analysis can help detect any changes in the transformer’s oil viscosity and composition, which can indicate potential issues before they cause failures.

Oil analysis can also detect any contaminants that can cause corrosion or insulation failure.

Maintenance and Inspections

Regular maintenance and inspections are crucial to ensure that transformers are functioning correctly.

During maintenance, the transformer’s cooling systems, insulation, and other critical components should be inspected and tested for any issues.

Any issues found should be addressed promptly to prevent transformer failure.

Transformer Location

The location of the transformer can also impact its performance during high ambient temperatures.

Transformers should be placed in areas with adequate ventilation and away from direct sunlight, which can increase their temperature. Additionally, transformers should be protected from high humidity levels that can cause corrosion.

What is the maximum ambient temperature that a transformer can be installed in?

The maximum ambient temperature that a transformer can be installed in depends on several factors, including the transformer’s design, insulation class, and operating conditions.

However, as a general rule, the average ambient temperature for a transformer over a 24 hour period should not exceed 30 degrees Celsius to ensure safe and efficient transformer operation.

For example, if the transformer ambient temperature was 40 degrees Celsius for 12 hours, then the transformer must not exceed 20 degrees Celsius for the remaining 12 hours to average a 30 degrees Celsius ambient temperature. If the average ambient temperature exceeds 30 degrees Celsius, the transformer’s capacity may need to be reduced to maintain safe operation.

According to IEEE C57 12.96, if the average ambient temperature exceeds 30 degrees Celsius, the transformer’s capacity must be reduced by 0.4% for every degree Celsius above 30 degrees Celsius. It’s important to note that this formula is only valid up to an average of 50 degrees Celsius, and using transformers above their listed ambient temperature can shorten their lifespan.

However, it’s important to remember that the impact of high ambient temperatures on transformer lifespan is influenced by other factors such as loading, frequency of use, and humidity. Therefore, it’s crucial to monitor the transformer’s temperature regularly and take appropriate measures to maintain a safe operating temperature.


Ambient temperature can significantly impact transformer performance, and it’s essential to take steps to protect them from overheating.

Cooling systems, regular oil analysis, maintenance and inspections, and proper transformer location are some of the ways to ensure that transformers remain within their temperature limits and function correctly.

By implementing these measures, transformers can operate efficiently and avoid costly downtime and repairs.