Guide to Replacing Transformers

The third part of the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6) was published earlier this month. Scientists warn that limiting global warming to 1.5°C is beyond reach but restricting temperature rise to no more than 1.5C to 2C could be the range that will minimize the likelihood of reaching critical environmental tipping points.

On a brighter note, the IPCC states that there is very high confidence (at least a 9 in 10 chance) that energy efficiency improvements, robust transmission systems and updated design standards on energy assets can reduce vulnerabilities to climate change. Here are some practical tips in the form of a checklist to address ageing transformer assets that could assist you in decarbonising your grid and meeting Net Zero commitments.


Find out how old your existing transformer is

A good starting point is understanding the age and condition of the transformer assets you have. A general rule of thumb is that the older the transformer is, the higher its energy losses would be. Through a Freedom of Information request we submitted to Ofgem, we found out that the average age of a distribution transformer in the UK is 63 years old! Transformers technology back in the 1950s focused mostly on the main job of transformers, converting voltage, with little regard to the energy efficiency of the process. In addition to the energy losses incurred, old transformers raise the question of the resilience of the network.


Understand transformer losses regulation

The European Commission estimated that 2.9% of all energy generated across EU27 and the UK is wasted through transformer losses. This amounts to 93TWh which is equivalent to the electricity consumed in Denmark over three years. To tackle the issue, the EU introduced new laws that regulated the load and no-load losses for distribution and power transformers. All transformers placed into the market or put into service in the UK and EU must comply with the Ecodesign regulations (read Tier 2 FAQ).

The EU introduced the regulation in phases; Ecodesign Tier 1 became effective in 2015 and Tier 2 became effective in 2021 with stricter design requirements. In the procurement process of new transformers, you need to make sure the losses are Tier 2 or lower unless the transformers were manufactured and placed in the market prior to July 2021, in this case, Tier 1 can be purchased (check stock).


Compare the energy losses of old vs. new transformer

We researched, took measurements of old assets and managed to gather information on historical transformer losses. The table below exhibits the load and no-load losses of different 1000kVA transformers depending on the year they were manufactured or which ecodesign regulation they follow.

You can see how transformers got more efficient with time. Here, at Wilson Power Solutions, we are very proud to be the manufacturer of the most energy-efficient distribution transformer in the UK, Wilson e3 Ultra Low Loss Amorphous Transformers (more details). 

Load Losses (W) No Load Losses (W)
1950’s 15625 2870
1970’s 15094 1770
1990’s 13125 1400
Pre 2015 12500 1350
Tier 1 (2015) Wilson e1 10500 770
Tier 2 (2021) Wilson T2 7600 693
Wilson e3 (Exceeding Tier 2) 6630 428


Understand space availability in the substation and relevant concessions

Tier 1, Tier 2 and Wilson e3 transformers across the market are bigger in size when compared to older transformers. Thus, one thing to check would be the General Arrangement drawing and dimensions (all GAs for our standard transformers can be found here) of the new transformer to make sure it fits within the space available.

There are multiple concessions mentioned in the regulation (watch our webinar recording that covers concessions) concession is given in some cases to install Tier 1 transformer instead of Tier 2 if there are space limitations. According to the regulation:

“In specific situations where medium power transformers (distribution tx) are being installed in existing urban substation locations, there can be space and weight constraints that affect the maximum size and weight of the replacement transformer to be used. Therefore, when the replacement of an existing transformer is technically infeasible or entails disproportionate costs, a regulatory relief should be justified.”


Schedule upgrades and keep in mind supply chain challenges

It is good practice to routinely service and maintain your assets. Being fully aware of the capability and condition of the assets and using this information to schedule upgrades can make your life easier. We have encountered on multiple occasions transformer failures leaving the site with no power. Options available would be a) to hire an emergency transformer in the interim (check out our hiring partner WATTS) but a transformer with a rating and voltage ratio that meet your site requirements might be limited and b) to try and source a transformer from stock. Although these transformers could be available in some cases, you shouldn’t rely on this approach especially if you are not after a box-to-box; it will take tens of weeks to manufacture said transformer with ancillaries, LV cabinets and switchgear and transport it to the site.

The biggest issues nowadays felt across different markets and industries are supply chain related. From volatile markets and raw material supply issues to geopolitical events and COVID recovery, all these have caused significant delays and availability threats to many sectors. Planning upgrades can avoid being subjected to all these issues. In addition, labour costs, energy prices, raw materials and transportation have increased worldwide so the sooner you make the decision the better.

Prepare a payback analysis to build a case for upper management

We have been offering our prospective customers a free-of-charge payback analysis for years. We compare your current assets against our Wilson T2 or Wilson e3 options showing you energy, carbon & financial savings both annually and across the lifetime of the transformer (30 years). We have also developed a simple online payback calculator to help you to estimate the savings you could be making! To calculate your potential savings, simply enter the transformer rating, load factor, age and the electric rate you pay. You can request a detailed breakdown that will automatically be sent to your email (check our transformer payback calculator).

In addition to the web service, we offer an in-depth analysis taking into consideration more details such as different electric rates for day & night or different transformer ratings, etc. You can request this service by filling out a form on our website, talking to one of our regional sales managers, or getting in touch with our Energy Policy Manager, Ayah Alfawaris.


Incorporate rising electricity prices in your feasibility analysis

We have been doing a great number of paybacks recently and one common poor practice we noticed is that customers only consider the commodity price in these paybacks. Businesses pay great amounts for extras on top of the commodity price for things like Renewables obligation, Standing Charge, Capacity Market Charge, etc. These charges form nearly half of the bill and a significant percentage of them are paid per kWh. Anything paid per kWh needs to be taken into consideration in the tariff used in the paybacks because this is can be a potential for extra financial savings.

Another poor practice is using the energy tariff you are on now without considering the massive increases that the UK wholesale market has witnessed over the past couple of years. Average price cap unit rates for commercial & industrial electric use in the UK have jumped from £0.145/kWh to £0.28/kWh in the past decade. On average, electricity contracts last for 3-5 years so if yours is year 4 and you pay 10p/kWh, your new rate in a year’s time will not be shy of 25p/kWh at best.


Study your load profile

The most significant energy losses in transformers are caused by two factors; No Load losses, also known as core or iron losses. These are present from the moment the transformer has been energised, so that’s 24 hours a day and 365 days a year. The second type is Load Losses or winding losses. As the name implies these are a product of the load current and their magnitude depends on the loading of the transformer.

Some sectors, such as data centres, regulate really low load factors for safety reasons but the majority of other sectors need to think of resource utilisation. A few questions to ask yourself, what is your load factor? The more the transformer is loaded and the more you utilise it, the more savings you will make. If the load factor is less than 50%, you might need to consider downsizing your transformer. Another question is what is your maximum half-hourly load? You need to take this into consideration if you are considering downsizing. The last and most important question is, have you forecasted load growth on this transformer? Understanding expansion plans like adding EV charging points should be considered as an increased load factor in the calculation.

Challenge the status quo through technological change

It is a common practice to adopt century-old technologies without questioning their efficiency as long as we are playing it safe. However, this could be a missed opportunity to reduce your carbon emissions. Two examples we can think of are amorphous vs. CRGO core materials and oil-filled vs. dry-type transformers.

We have been manufacturing and supplying super-low and ultra-low loss amorphous transformers to the UK market for 14 years now. We have over 1300 amorphous transformers installed across the kingdom with zero failures related to this technology. Amorphous core material is far more easily magnetised than standard core steel due to its random molecular structure. This means less friction is created during the magnetisation process and therefore less heat is produced resulting in lower hysteresis losses and more efficient transformers. Our Wilson e3 is 15% more efficient when compared to strict Tier 2 loss specifications.

Ecodesign regulation is not technology-neutral; for example, Tier 2 specifications for oil-filled transformers are much stricter than they are for dry-type transformers. This means that dry-type cast resin transformers result in higher energy losses when compared to their oil counterparts. Taking the case of a 1000kVA transformer, Cast Resin energy losses are 25% and 47% higher than Tier 2 (Wilson T2) and Wilson e3 transformers respectively. 


Communicate the existing substation specifications and site requirements

It always helps our engineers to be aware of any specific voltage rations, ratings, impedance levels, ancillaries, switchgear, cable connections, etc. that your site needs. Knowing this at the design phase can help us avoid issues later on and can help you save money on modifications. If you have any site limitations or special projects, like fitting transformers inside your wind turbine tower, talking to our team helps you explore all available options.


Check out available funds and financing options

Depending on your SIC code and the sector you operate within, you might be eligible for government grants and financing options. For example, Salix funding for public buildings or the Industrial Energy Transformation Fund for manufacturers and data centres (read blog). Follow our LinkedIn page as we tend to share opportunities for funding as we learn about them.


We have shared multiple blogs about the energy, carbon and financial savings of replacing old transformers and upgrading infrastructures. We hope this checklist helps you in organising your thoughts and building a strong case for the replacement to get the approval for the upgrade investments.

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