Top threats to a wind farm’s transformer fleet

Considering the global charge to achieve net-zero, an increasing amount of wind energy generation farms are in development around the region along with the electrical assets needed to connect the generation sites to the national grid. Although wind power generation is a growing electricity source, it comes with numerous challenges regarding the various aspects of integrating large-scale wind generation units into the UK’s national grid.

Transformers in general, function as a single point of failure meaning that if these transformers suffer a critical failure due to an undetected fault, this can result in plant downtime. However, a transmission transformer on a wind farm operates in an environment unlike its utility counterparts and is subject to its own unique stresses. On average a critical failure can last up to 18 months and risk an wind farm up to $75m in lost revenues. Depending on the wind farms installation type, particularly offshore wind farms, transformer repair and/or replacement can be even more challenging due to weather conditions and transport logistics - greatly increasing the length of downtime and cost of repair to the transformer.

We have identified several threats to the transformer and what actions can be undertaken to extend the assets life and prevent costly failures which can have financial impact to the wind farm.

1. Variable load patterns

At times, wind acceleration can go below the cut off speed of the generator leading to it being taken offline. This leads the transformer to experience a consistent amount of thermal cycling as it has no-load to load and then back to loading high amounts of energy. Thermal cycling, and thermal expansion and contraction can have harmful effects on the transformer, it may compromise transformer gaskets and seals and it can accelerate aging and degradation in solid insulation materials. This may affect the condition of the transformers oil causing absorption of moisture or rates of ‘gassing’ in some instances. These degradation processes eventually lead to a decline of the transformer’s insulation resulting in the transformer being taken offline for a period of time to conduct essential maintenance such as replenishing the oil.

2. Higher loading targets

Due to the current political and economic situation of today’s competitive pricing for energy, low carbon energy sources are becoming a more responsible source of electricity in the UK’s energy mix. This places increased pressure to produce as much energy as possible when the generation opportunity is available. This can lead to transformers being under increased stress from a higher load target. A higher load results in higher heat being generated from the transformer causing the transformer insultation to age more rapidly. This can reduce the assets life and result in downtime of the plant to allow asset managers to conduct regular manual inspections to assess the level of degradation.

3. Environmental factors

Transformers located on offshore wind farms are subjected to more frequent voltage transients due to wind gusts, transients from lightning strikes, and swells. This can produce vibrations in the transformer which can introduce mechanical stresses, causing severe damage to the insulation components. Furthermore, the saline air and levels of ultraviolet radiations can lead to more rapid corrosion of transformer gaskets and seals, leading to preliminary oil leaks and may compromise the transformer oil preservation system which prevents humidity from entering the transformer and degrading its insulation system. Again, this will have a significant impact on the transformers average life cycle and will require additional repairs and more regular maintenance – both of which means downtime of the entire wind farm.

4. Lack of transformer experts

Many industry experts within asset integrity management argue that poor asset management can lead to inefficiency in the delivery of the lifecycle of renewable energy assets. An example of this can be an increase in downtime and higher costs of operation and maintenance resulting in higher Levelised cost of electricity (LCoE) and thus decreased profits. Therefore, it is imperative that asset managers operating on a wind farm are supported by asset experts. Unfortunately, it is not always possible to have an expert on hand for every component on a wind farm, this is particularly true for transformer experts given the decline in this talent pool. Due to the complexity of transformers, asset managers should have access to an advanced transformer monitoring solution which can offer critical insights into the health, risk profile and performance of their fleet.

5. Through fault current

The largest cause of transformer failures is due to external events, in particular, through faults which are responsible for 20%+ of failures. Transformers for wind generation are required to have Fault Ride Through Capability to maintain stability of the transmission system during fault events. This requirement differs from regular substation transformers, which are normally tripped off to isolate a fault. Therefore, transformers in wind generation are required to endure more stressful fault conditions that may affect their long-term reliability meaning that a replacement for the transformer may have to be conducted earlier than your average asset.

The challenge for asset managers is to find faults in their infancy, reducing expensive maintenance activities, and minimising the risk of plant downtime. Transformer monitoring solutions can address these challenges and help asset managers overcome the threats listed above.

Camlin Energy's TOTUS transformer monitoring solution monitors all key components of a transformer and provides early fault diagnoses and detection. For example, TOTUS can deliver insights into which transformer is most at risk within the fleet whilst also providing visibility of the integrity of the assets insulation to help assess the mechanical strength of the transformer and the risk for mechanical damages to these threats.

Our transformer monitoring solutions examines the stress caused by the biggest risks to transformers such as through faults and cellulose ageing due to combined action of temperatures, moisture, and oxygen. Featuring an embedded advanced alarm management system, TOTUS drives efficient maintenance scheduling for asset managers, with alerts only triggered when there is an issue with the transformer. This enables asset managers to focus resources on the transformers that are at risk, reducing the potential of a sudden transformer failure and protecting availability KPIs.

By partnering with Camlin Energy, we can help wind farm asset managers to implement a fully condition-based maintenance schedule for these critical assets, allowing them to optimise their asset management strategy. This into enables them to manage insurance costs as they have a clear view of the safety, reliability, and risk to the company’s revenue.

To discuss the threats highlighted in the blog and the benefits of investing in an advanced transformer monitoring solution for your wind farm, get in touch using the form below.