Transformers are equipment that are part of the generation and distribution of electrical energy. They can be divided into two main categories: oil-filled and dry. Dry-type transformers get their name precisely because they don't need oil for cooling or insulation. But do you know how cooling happens in this type of equipment? Follow along and understand the characteristics of dry-type transformers. 

The importance of transformer cooling
During the operation of transformers—and other electrical equipment—there is an energy loss that transforms into heat, warming the insulating materials. When excessive, this heat can damage the equipment, reducing its lifespan and causing failures. Thus, cooling is essential to ensure that all transformer components remain within the recommended temperature range, preventing accidents. 

Oil transformers
In oil-filled transformers, as the name suggests, this cooling occurs through the use of insulating liquid. Thus, the windings and the core are surrounded by the insulator, which reduces heat from the internal area of the radiators. Meanwhile, the outer part of the radiators is cooled as a result of contact with the ambient air. This type of equipment is common on power poles.

Dry transformer cooling
Dry-type transformers use only ambient air for cooling and insulation. The air circulates between the coils through design-specified ventilation channels, forcing the cooling of the windings. Therefore, they can be installed in enclosed environments and close to operations, without posing risks and ensuring great effectiveness. This type of equipment is commonly found in commercial buildings, theaters, movie theaters, data centers, hospitals, and various types of industries, from mining to civil construction. 

Dry-type transformers for your needs
Do you work with any of the mentioned segments and have identified the need for a transformer for your energy operations? Speak with our consultants and discover the ideal dry-type transformer options for your needs. 

All transformers require continuous inspection to ensure the proper functioning of the equipment. And the electrical transformers, which are used in the generation and distribution of energy for industries, hospitals, airports, and cinemas, are no different. However, it's worth highlighting that they require specific tests, which allow for the prevention of unscheduled shutdowns, extending the equipment's lifespan, and forecasting maintenance needs, thereby reducing the downtime. Do you know how preventive maintenance for dry-type transformers is performed? Understand below the routine tests, according to Brazilian standards (ABNT – NBR 5356).

Learn how preventive maintenance is performed on dry-type transformers
As previously mentioned, the goal of preventive maintenance is to assess the equipment, understanding its integrity and potential for failure. This is done through various tests that compare the equipment's results with factory (design) data and in accordance with Brazilian standards. Check out the step-by-step process below. 

Site inspection and cleaning
Analysis of the transformer installation site, visual inspection of the equipment, temperature check, and cleaning of air inlets and outlets. 

Noise presence check
Monitoring of the sounds produced by the equipment and comparison with the expected in the project. 

Turns ratio test
Its purpose is to ensure that the number of turns between windings is in accordance with the design. This ensures that the input and output voltages are maintained within a range of plus or minus 0.5% between the actual and designed values. 

Ohmic resistance test of windings
The essay aims to Analyze possible interruptions or connection and contact issues. It performs this diagnosis  when comparing the calculated values as ideal in the equipment design versus the values measured on it. 

Insulation resistance test
The objective is to verify the solid insulation levels of transformers between windings and ground, which can be compromised due to the presence of dust, moisture, and material degradation.

Applied Stress Test
This involves applying a specific voltage to the equipment at intervals determined by the standard. During the process, to ensure the transformer is functioning as expected, there must be no insulation breakdown.

Induced Tension Test
The test consists of applying double the nominal voltage, with a frequency of at least 120Hz for the time calculated by the standard. During this period, there should be no disruptive discharges. If they occur, the equipment requires maintenance. 

No-load test and excitation current
Perform loss measurements through nominal voltage and frequency, and compare the obtained values with the design and standard.

Are you looking for a qualified company to perform preventive maintenance on dry-type transformers? Transformadores União's laboratory has modern, calibrated, and prepared equipment to validate medium and low voltage transformer tests, as required by ABNT standards. Contact us!