Extending Transformer’s Life Expectancy with Condition Monitoring

 

Transformers provide safe and effective power distribution and transmission in modern power systems and electrical networks. Therefore, the benefit of a power utility is in the long service life of transformers - somewhere between three to four decades.

However, many transformers age prematurely and lead to an increase in operational and maintenance budgets, unplanned downtime, and affect the network reliability of utilities.

This is where condition monitoring systems step in. These systems help enhance transformers’ service life by preventing premature aging.

In this blog, we look at the factors causing premature aging of transformers and how condition monitoring systems help boost their life expectancy.

Common Factors That Initiate and Accelerate Transformer Aging

Transformers provide safe and effective power distribution and transmission in modern power systems and electrical networks. Therefore, the benefit of a power utility is in the long service life of transformers - somewhere between three to four decades.

However, many transformers age prematurely and lead to an increase in operational and maintenance budgets, unplanned downtime, and affect the network reliability of utilities.

This is where condition monitoring systems step in. These systems help enhance transformers’ service life by preventing premature aging.

In this blog, we look at the factors causing premature aging of transformers and how condition monitoring systems help boost their life expectancy.

Partial Discharge (PD)

Partial Discharge involves localized discharges that take place inside the insulation system of transformers. Usually, cracks or voids in insulation or entry of contaminants under high voltages create pathways for discharges.

Slowly, PD degrades the insulation material, especially paper and pressboard. It is the beginning of a complete breakdown.

It is observed more in older transformers. If not resolved on time, it not only fails transformers but also has the potential to crush the reliability of an entire electrical system.

Oil Contamination and Oxidation

Oil plays a double role in transformers: as an electrical insulator and thermal conductor.

Over time, oil undergoes oxidation due to extreme temperatures, exposure to oxygen, and catalytic activity happening on metal surfaces.

This oxidation process produces:

• acidic by-products that erode cellulose insulation and cause metal parts to corrode.
• moisture, which weakens dielectric strength and makes insulation brittle.
• sludge buildup, which chokes cooling ducts, increasing temperature levels inside the core. This in turn speeds up oxidation, creating a harmful cyclic reaction.

Thermal Stress and Winding Hotspots

As per the Arrhenius equation, every 6 to 8°C rise in temperature doubles the rate of chemical degradation.

• Localized hotspots: Irregular distribution of load between phases, cooling issues due to obstructed oil ducts, poor circulation, or faults in windings create hotspots localized regions inside a transformer that become hotter than the average operating temperature.

• Thermal Stress: Thermal stress splits long cellulose chains into shorter chains. This creates cracks or voids due to weakened insulation. It also results in partial discharge.

Overall, cellulose insulation starts degrading rapidly under extreme heat, contributing to a reduction in the transformer's life expectancy.

Moisture Ingress

Moisture is a hidden aging accelerant in transformers.

High moisture levels:

• increase the frequency of internal flashovers as they reduce dielectric strength.
• form bubbles due to thermal stress. These bubbles break down the dielectric.
• sludge buildup, which chokes cooling ducts, increasing temperature levels inside the core. This in turn speeds up oxidation, creating a harmful cyclic reaction.

How Condition Monitoring Extends the Service Life of Transformers

Transformer condition monitoring systems produce comprehensive health reports by utilizing IoT sensors, advanced communication protocols, and analytics. This continuous tracking of health and performance of transformers assists in optimizing repair and maintenance schedules.

Real-Time Fault Detection

IoT sensors measure parameters such as hotspots and PD in real time. This makes it possible to detect discharge activity at an early stage. As a result, it becomes possible to carry out necessary repairs to avoid further insulation degradation.

Additionally, consistent oil quality analysis and dissolved gas analysis (DGA) help identify oxidation by-products and moisture ingress. This informs the service team in advance that it is time to filter the oil or replace it to ensure the mechanical and electrical integrity of the insulation.

Temperature Sensors and Thermal Imaging

Integration of temperature sensors and thermal imaging into monitoring systems helps manage thermal stress and winding hotspots, allowing operators to upgrade cooling measures or distribute the load properly.

Similarly, humidity sensors report moisture levels in the insulation and oil. Based on the data, operators decide if they should initiate drying processes or sealing should be improved.

Conclusion

In conclusion, transformer condition monitoring is essential to extend operational life of the equipment. It detects faults like partial discharges, oxidation, and thermal hotspots. It helps execute proactive maintenance activities and avoid expensive repairs or replacements.

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