Transformers are a vital component of electrical power distribution systems and are required to step voltage levels up or down to provide stable power. However, like any piece of large equipment, transformers are susceptible to wear and tear. Without regular maintenance, transformer performance deteriorates, causing failures that disrupt operations, create safety risks, and cost thousands of dollars in downtime and repairs.
Although not all transformer failures can be predicted, many can be prevented. In this article, we’ll explore the most common reasons they fail, along with ways to prevent and mitigate the impact of failure.
Key factors that can cause transformer failure
These factors can lead to transformer failure:
- Natural disasters
Natural disasters are the most unpredictable cause for transformer failure. Both earthquakes and lightning strikes can cause problems. Lightning can disrupt the electrical operation, while earthquakes can vibrate connections loose, leading to short circuits. Installing anti-vibration pads and lightning rods can protect a transformer from these two potentials.
- Overheating and thermal stress
Transformers generate an enormous amount of heat, and while the insulation is supposed to dissipate that heat, excessive temperatures can degrade that insulation and other internal components. Prolonged exposure to extremely high temperatures reduces the dielectric strength of the insulation and increases the potential for internal faults.
Overheating can be caused by excessive demand, inadequate ventilation, a malfunction of the cooling system, high external temperatures, and poor environmental conditions.
- Moisture and contamination
Moisture and environmental contaminants can compromise a transformer’s insulation and promote corrosion. These issues are often caused by leaky gaskets, bushings, and seals, and condensation that forms inside the transformer.
When insulation becomes wet, there’s a higher chance of short circuits and premature breakdown. To avoid this issue, it’s crucial to test for moisture content in oil-filled transformers, inspect seals and gaskets, and use silica gel breathers to absorb moisture in both oil-filled and dry-type transformers.
- Oil degradation and insulation breakdown
In oil-filled transformers, the oil acts as a coolant, but over time, oil can become compromised by heat, oxygen exposure, and contaminants. Once oil degradation takes place, it loses its dielectric strength, which increases the potential for electrical faults. Worse, sludge can form and block the cooling channels, leading to overheating.
It’s crucial to perform regular oil testing, including Dissolved Gas Analysis (DGA), acidity testing, and water content evaluation. Transformer oil should be filtered and replaced as needed based on color and transparency.
- Electrical surges and faults
Transformers are vulnerable to electrical surges, which can lead to catastrophic failures if there are no protective measures in place. These surges can be caused by lightning strikes, system faults, and transient overvoltages. Some electrical surges can puncture insulation, damage windings, and cause bushings and tap-changers to fail.
Protective measures can reduce the risk of surges and faults. This includes installing and testing surge arresters, inspecting protective relays, and testing the resistance of insulation to identify weak areas that need to be replaced.
- Mechanical stress and aging
As transformers remain in operation, they experience mechanical stress caused by load cycling and naturally aging components. This can be caused by load fluctuations, vibration, and aging insulation. Mechanical stress can cause core displacement, deformed windings, and structural fatigue, which all increase the potential for internal faults.
To mitigate the impact of mechanical stress and aging, it’s crucial to check for abnormal vibration during inspections, perform a physical examination of the windings and core alignment, and test for deteriorating components.
Best practices for transformer maintenance
Maintaining transformer health requires preventive, predictive, and corrective maintenance strategies.
Preventive maintenance includes:
- Regular inspections. Check all bushings, seals, and cooling systems
- Regular oil testing. Test for moisture, gas content, acidity, and other contaminants.
- Radiator cleaning. Radiators and cooling fans need to be cleaned regularly for proper heat dissipation.
Predictive maintenance includes:
- Monitoring systems. Sensors connected to an app can monitor transformer performance in real-time.
- Partial discharge testing. This is used to identify weak insulation.
- Thermographic surveys. This will catch abnormal heating patterns.
Corrective maintenance includes:
- Parts replacement. Replace degraded components promptly.
- Repairing leaks. Seal all areas that are vulnerable to leaks.
- Addressing faults. Identified faults need to be addressed before they escalate into larger problems.
Transformer maintenance is critical
Preventing transformer failure isn’t hard, but it does require starting with a high-quality transformer built by a reputable manufacturer. No matter how perfectly you stay on top of maintenance, a poorly-built transformer is bound to fail prematurely. However, a quality transformer, a regular maintenance plan, and prompt repairs can enhance reliability, extend transformer lifespan, and avoid costly downtime.
