Knowledge Centre

The critical role of transformer monitoring and why it matters.

Insight,
Kelvatek
10th May 2024
The critical role of transformer monitoring and why it matters

The critical role of transformer monitoring and why it matters.

As the renewable energy market continues to grow, so does the need to understand asset availability and optimise operation and maintenance strategies. Asset Managers are now facing the challenge of identifying and investing in the right technologies to deliver insights into asset health to reduce risk and maximise performance.

A key asset within a wind farm is the power transformer which connects wind energy generation to the electricity grid. Transformers generally function as a single point of failure, which means that undetected faults can result in plant downtime and loss of revenue.

Understanding the risk to the transformer in real time, is critical. Transformer monitoring improves transformer reliability by providing early warning to developing faults. This enables operators to prevent failure and reduce risk to operations.

What to monitor and why

The step-up transformers located both on the offshore substation and those onshore connecting to the wider transmission or distribution system are critical parts of an offshore wind project. If the key components of these crucial assets are not in good working order, the wind farm will be unable to transmit energy to the wider transmission system.

Traditionally, these assets are visually inspected for degradation, and specialist equipment is used by operators to manually inspect substation infrastructure such as transformers to check for unusual changes in operating behaviour. These are often done on a periodic basis, with no consideration for the actual condition of the transformer itself. The process is manual and can give unreliable or misleading results due to inconsistencies in reading methods or other sample retrieval inconsistencies especially in relation to manual transformer oil sampling. Adopting online continuous monitoring can alleviate all the negative effects associated with periodic manual inspections.

Although power transformers are static machines, with a relatively simple working principle, they are complex assets, as they are made up of several materials, such as copper, iron, solid and liquid insulating materials like paper, wood, porcelain, resin, and oil. Such materials are prone to different failure modes that can affect the main tank, bushings, tap changer, oil conservator, cooling system, etc.

Combining these elements and ensuring they last for their entire design life is not an easy task. During operation, transformer components are constantly subjected to various stresses including:

• Electrical

• Thermal

• Mechanical (vibration)

• Chemical

Components more likely to cause failure

These stresses can lead to the formation of defects inside the transformer; often referred to as faults. The transformer is the main artery through which power is delivered to the transmission network from a wind farm; a transformer failure likely results in significant downtime for the entire wind farm. When considering transformer failures, some components are more likely to cause transformer failures than others. According to data published in the CIGRE 642 Transformer Reliability Survey, the components most likely to be involved in transformer failure are:

Windings

Transformer windings

The Risk

Transformer windings are the most likely component to be involved in a transformer failure; an estimated ~37% of failures.

The Impact

The operational conditions within wind farms can impose additional stresses on the transformer windings, which can increase the risk for winding faults in wind farm transformers. Operating periods under high load, mixed with periods of intermittent/variable load occur more frequently in wind generation due to the variable nature of wind energy. This can increase the risk of electrical faults in the transformer.

Tap changer

Tap changers

The risk

Tap changers are the next most likely component to be involved in transformer failures; an estimated ~30% of failures.

The impact

Like transformer windings, the on-load tap changer may be more stressed in a wind farm installation. Periods of variable loading and changing load may require the tap changer to operate more frequently in order to regulate the voltage. More frequent use imposes more wear and tear on the mechanical operating mechanisms in the tap changer.

Bushing adaptor

Bushings

The risk

Bushings are typically present in onshore substations however they are not always present in offshore wind installations as many offshore platform transformers are terminated directly by submarine cables. When bushings are installed, they are the third highest component involved in transformer failures, an estimated 18% of failures.

The impact

For coastal transformers, exposed to the elements, the saline air around offshore installations can increase the risk of contamination on bushing surfaces, which can lead to electrical discharges and stress on the bushings.

By investing in a digital transformer monitoring solution, Asset Managers can gain increased visibility and insight into the health, risk, and performance of these components and their assets. With this, the wind farm owner can also gain a better understanding of the potential risks to availability and revenue. By being better equipped with more appropriate data and insights on their critical assets, wind farm owners and operators can make more informed decisions: Transformer Monitoring: A strategic blueprint for wind farm success

Transformer Monitoring: A strategic blueprint for wind farm success.