➡ Norm Bowdler Contractor (VTAC Technical / AJ Video). Something to ponder, when a xfmr failure does occur is it always associated with a fire, buncefield was a total disaster as the bunds failed due to the mastic gaps melting between the concreted sections.

➡ Catherine Falconer Commercial Contracts Manager at (Scottish&Southern Electricity Networks). Something regularly discussed within DNOs….

Since August 1985 Eden have been testing and maintaining the insulating liquids in transformers and switchgear in the United Kingdom, Belgium, France and Germany.

➡ Martin Kempler (Estimator). Exactly. Though you might need an interceptor on the drain just in case of a spill washing through

➡ Neil Denbow (Director at Eden Transformer Oil). Transformers in service are not storage tanks and so not applicable to these regulations (the Environment Agency website is wrong and they have confirmed that in an email to me but over a year later have not changed their text). However, page 69 of BS EN 61936-1:2010 (titled Power installations exceeding 1 kV a.c. Common rules) is applicable and that states transformers holding more than 1,000 litres need secondary containment. Of course bunds can be retrofitted. Please see my post last year https://www.linkedin.com/feed/update/urn:li:activity:6336239479648514048/ I hope that is helpful.

➡ Andy Beckton (Electrician). Double tank transformers like they double hull oil tankers-no need for a bund then-fit a level switch, then if it leaks-repair it!

➡ Craig Davies Senior Electrical Engineer – (Navitas Engineering Ltd) This has been debated many times in the Rail industry. With respect to Environmental Agency website error, certain parties in Rail industry have received same letter from Environmental Agency but certain representatives contradict each other in their response.

➡ James Hoare LHW Partnership (Electrical & Energy Engineers). Does not surprise me one bit,and agree – the good news is an O&Ms  are spending some ££ on routine sampling etc. We used to make £1000s and the transformer failure rate was almost zero, even the cast resins which at the time were new technology.

➡ Neil Denbow (Director at Eden Transformer Oil). I certainly agree with that Graham. We see the good the bad and the ugly. We offer inspect, sampling and analysis services.

➡ Karl R (Functional Safety & Systems Engineer). Watch out for an error in the HSE publicised “Hierarchy of Controls” leaflet. The vitally important area of physical isolation was missed. The hierarchy is actually: 1 Eliminate – do it a different way that doesn’t use the hazardous methods or substances. There’s no risk if there’s no hazard. No need to mitigate for a non existent hazard. Save effort, money and time for use elsewhere. 2 Substitute – use something non/less hazardous 3 Isolation – Physical separation. Barriers, bunds, locked areas and vessel containment. Dual layers. 4 Design – Automation, control, monitor, report and safely shutdown/reroute. Engineered solutions to mitigate hazardous situations and prevent hazardous material release. Control and safety systems to look after the process. Switchgear protection. 5 Admin – Enforcement and training. Emergency Response Procedures. Authorised areas, Competency, Risk Assessments, Design Reviews, Method Statements, verification and validation, maintenance, etc. 6 PPE

➡ Robert Copley Midel (M&I Materials Limited). Retro fitting bunding is difficult on an installation like this and expensive. As an alternative you could retro-fill with MIDEL 7131 which is Biodegradable and fire safe, this is a lower cost option while increasing the performance, lifetime, safety of the transformer and also helping to protect the environment at the same time! Something Neil and his team at Eden have done many times already.

APE aim to provide their clients with comprehensive solutions and support, this support package may be as simple as design and commissioning services through to a full design and build power plant.

➡ Andrew Hawley Group MD, CMBC CEF Chair, RICS Trainer. Depends on circumstances & client budget (sadly!).. always try transformer bund if budget allows, only essential if installing in sensitive or enclosed areas, for example – an oil filled Tx caged in the corner of an underground car park should be bunded but in a wide open space with no potential for contamination of other equipment or the environment, bund if budget allows. Also consider the quality of the transformer and in all cases ensure a proper maintenance regime is in place.

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➡ Neil Probert (Electrical Power Engineer to 66kV). Only for transformers that are under specified, aluminium wound and designed to fail

APE “care” and in order to satisfy your needs they “listen” ; APE listens to how your business operates, listen to your concerns with regards to the implementation process, and liaises with third parties as part of their duties or in support of you directly.

➡ Nigel Tongue. Bunded concrete pit with the TX on raised plinth in the centre. The correct type of gravel surrounding it. Tube installed so you can see the bund bottom and pump out rain water. Historically that’s how we install.

Question to all my fine Engineering contacts regarding oil filled distribution transformers – transformers are exempt from the UK oil storage regulations, as they are oil using (cooling) rather than storing, unless they have a conservator, holding in excess of 201lts, connected by single pipe – I see many transformer installs, including DNO installations, that do not have bunds around the transformers.

➡ Jason Rowley Director (Jason Rowley LTD). I had a project with a DNO similar to the picture above where on the weekend after they dropped it on site a nice local decided to empty the transformer oil and steal 3 copper washers from it. (It was an aluminium core) The clean up cost over £60K as we had to excavate nearly 4 meters to remove the contaminated ground then rebuild the whole compound again. Project was quoted at £20,000. I would pay an extra £1000 for a bund if I ever do another.

➡ Martin Mathiasen Senior HV Technician, Transformer Specialist (Present Group). Hazard vs Risk and Consequence. Although the risk is low the consequence of hundreds if not thousands of litres to ground does warrant a suitable control measure. Bunding and directed pressure relief systems are the most suitable system of control. (In my opinion).

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➡ Peter Thomas (Grid Connection Engineer Renewables). For smaller distribution transformers of which there are many tens of thousands installed over the last 50+ years it’s a matter of asset and risk / management. It’s generally true that none are bunded as failures are rare to the point of being insignificant. If otherwise there would be public concern. And what about pole mounted transformers? They are more likely to experience failure due to overloading. Comments?

Former employees of Burmah Castrol, they realised that the vast majority of electrical engineers were simply replacing expensive transformer oil without fully appreciating the additional technical benefits of purification to the electrical equipment that Eden could achieve using a more convenient solution at a significantly lower cost.

➡ Neil Denbow (Director at Eden Transformer Oil). Dan, you are right that MIDEL is readily biodegradable but BS EN 61936-1:2010 doesn’t differentiate between oil, synthetic or natural esters. However, insurance companies do.

➡ Martin Kempler (Estimator). It’s a containment issue in case of fire or contamination. Landfill tax on hazardous waste is punitive

➡ James Hoare LHW Partnership (Electrical & Energy Engineers). Would agree in PV. Seen 1000 kva standard distribution transformers connected to 1000 kva inverters which generate a sine wave with a level of harmonic content which should necessitate derating of transformer. The peak duty of transformer is when sun is out and ambient temp high , and will spend ( in uk) months far lower than peak output . As PV is cyclic the air / moisture content will cycle day and night so have to be a higher risk of premature failure – cast resin are in many ways better for inverter fed systems as the ones with foil windings cope better with heat rise from harmonics as more surface area on winding – a lot have gone into operation with little attention to lifetime longevity and I would argue a transformer with good maintenance correctly sized should last a long time.

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➡ Mark Rowcroft Technical Manager (Banks Renewables). I’d want to see a bund regardless. Minimal cost consideration but of huge benefit should you ever need it.

➡ Neil Denbow (Director at Eden Transformer Oil). For distribution transformers yes you can but the process should be carried out by an accredited MIDEL Service Partner (we were the first). For power transformers yes but with referral to M&I Materials. There have been many successful retrofills around the world – MIDEL 7131

➡ Marcus HoldenManaging Director (Torus Engineering Ltd). We cover both Power Generation and contaminated land.  If transformer oils still contain PAH’s – as they used to on the sites we have tested, the answer is a no brainer – bund them every time.  The clean up costs on Poly Aromatic Hydrocarbons is extremely expensive as Alan has already mentioned.  PAH’s are particularly nasty and can spread like wildfire through surface water transmission.

➡ Neil Denbow (Director at Eden Transformer Oil). Andrew, transformer bunds are essential if you are going to follow British Standard BS EN 61936-1:2010. They aren’t very expensive in the scheme of things and can be retrofitted.

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➡ Alan Guiver MIDGTEDirector (Agren Power and Energy Ltd and Agren Inspection Services). Bund them. I’ve always bunded transformers, and on one build on an existing concrete slab we used pre manufactured bund trays for 2.5Mva units, complete with rainwater / oil separator drains. De contamination costs run into many thousands if you have an issue- and leaking transformer oil spreads like you wouldn’t believe.

In this original post from LinkedIn, the business and employment-oriented social media network, Carl discusses transformer bunds with gathered opinions from industry peers featured in the thread of comments below.

➡ Philip Fenwick Contract manager (Qualified). Why can’t the heat from these oil filled transformers be used and or sold onto premises close by, this would then make these more environmentally friendly and spread the costs.

James, solar farm transformers do get a harder life than some sites and not all are up to the job Yesterday we analysed and reported on 46 Routine and DGA samples for one O&M (various sites and manufacturers), of the 46 transformers 12 had issues. I wouldn’t expect to see that fail rate at factories, offices, hospitals etc.

➡ Andy Ledward MSc MIET (Project Manager). Good question Carl. My experience is DNO tend not to bund their Distribution Transformers (Primary and Transmission yes). However (& forgive me if the policy has changed in some way) if you were to submit a design with a bund then this would be outside of the adopting DNO standard and would need to be approved as a special case, plus the cost to maintain etc. So I stand to be corrected if I am wrong, but this is an additional factor to consider as well as the environmental one.

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➡ Neil Denbow (Director at Eden Transformer Oil). Richard, larger 11kV transformers will have oil/water separation systems, smaller transformers will have valve with a oil/water capture filter that allows water to pass through but trap oil. We sell the latter on our website www.edenoil.co.uk and have a partner for the lager systems:- When a bund has not been maintained or doesn’t have filter system, we offer a bund emptying service.

➡ Karl R. (Functional Safety & Systems Engineer). The heat given off from these transformers is no more than 50C normally. Some large factories have sub stations and transformers inside, so heat would benefit the building. Most often these transformers and their isolation switches are outside, for various practical reasons.

➡ Carl A. Watkin thanks Gordon – would you bund all transformers regardless? I agree with earlier posting that bunding should be considered following a suitable and sufficient risk assessment based on many factors – from experience, there are more unbunded than bunded

➡ Muhammad Mushtaq Vohra (MSc Energy Management and Conservation at Middlesex University London). That’s true. Transformer above 1000kVA needs bunding.

➡ Derrick Stableford P.Tech.(Eng.) (Electrical, Instrumentation and Controls Designer at Associated Engineering). Funny I had a containment question at work this week. Sorbweb matting would be my answer for leak control. Most trannys at this level have level switches as options, the hard part is the comms back to the control centre, without creating a cyber security intrusion risk. The sorbweb Mat adsorbs oil, and repels water. No need for a shed. Using food grade oil will also help with environmental risks. You could fry your lunch with a drawn off sample, or bang it in your diesel. The bunding and double wall systems have their own cost adders and maintenance issues, Inc water pump outs and disposal. Mechanical separators can freeze and fail, esp. here at severely minus temps.

➡ Derrick Stableford P.Tech.(Eng.) (Electrical, Instrumentation and Controls Designer at Associated Engineering). We have a similar issue over here, in Canada. However our clients near rivers use food grade oil, Canola based. Also I’ve recently come across some adsorbent mats that repell water, but adsorb the oil. These are covered is some gravel, so the clean up costs become nominal in an event of spills. , and no oil/water separator is needed. They even work at negative temps. The only issue with the food grade oil, is that if energising at say -20c you need to warm the core, for a day or 2 so the unit doesn’t trip out on start up.

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➡ Richard Emery IEng MIET MIHEEM Authorising Engineer (E) IHEEM AE(E) at Green Building Design Consultants. Its a cooling medium. The oil circulates around the core and out to radiators on the sides, so aiding the cooling of the transformer core

➡ Raja Ratnam General Manager Construction, Minerals & Metals (Schenck Process Australia) From my point of view, transformer oil is never good to have risk of going into waterways – through drains or spread by stormwater. Also good fire containment with bunds. The risk is too great.

Eden provides end-to-end MV HV services and products to maintain transformer oil, MIDEL 7131 and silicon insulating liquid. On their webpage “Why Maintain Oil”, they highlight how Eden can provide a safe, economical and environmentally sound solution to maintaining transformers.

➡ David Pinning BEng (Hons) (Open) IEng MIET (Palm Paper Ltd). Carl, excellent post. We have fully bunded 132/20kV 63MVA units on site (ours, not DNO). Our bund system serves two purposes. Of course to contain the entire quantity of oil of one unit + excess for rainwater etc. for environmental protection. Secondly we pipe away the bunds to an underground fire quenching pit designed to both minimise secondary fire damage and permit a credible chance of extinguishing a transformer fire!

➡ Peter Thomas (Grid Connection Engineer for Renewables). James, yes that’s about it. 200kVA is normally the max size at 11 kV. However the failures are more likely to occur on old 5kVA single phase units which are often overloaded if the LV fuse has been incorrectly oversized which can and does occur. Many years ago I went to one failure in Snowdonia where it had burnt out. Only to discover it had over 30 kW of industrial fan heater attached which were used to warm up a climbing group after a climb! Needless to say we sorted it out.

➡ Neil Denbow (Director at Eden Transformer Oil). Manuel, BS EN 61936-1:2010 doesn’t differentiate between breathing and hermetically sealed transformers, it is defined by the volume of oil in the transformer.

In more recent years the treatment of transformer oil is the first choice for a cost effective and efficient maintenance program: the increasing cost of new oil, the importance of productivity and equipment downtime, coupled with the environmental benefits of avoiding the transportation of hazardous waste and use of virgin products, are all part of the equation – this applies to medium/high voltage (MV-HV) applications distributing electrical power at 11kV, 33kV and up to 66kV.

➡ Tony Haggis Director (Tony Haggis Consulting Ltd). Hazard control should follow the hierarchy: 1. Eliminate the hazard 2. Reduce the hazard 3. Control the hazard 4. PPE. Pole transformers are not ‘reasonably practicable” to protect using HV fuses, particularly for LV side faults. Effective bunding is impossible. The most difficult zone is the tails from transformer to LV fuses. UK DNOs generally use double insulated single core cables fitted with plastic cleats and fixed to a wooden pole. LV fuses are single phase plastic units seperated 300mm apart, again, fixed to a wood pole. Phase to phase and earth faults are virtually impossible. Lightning takes out a lot of pole transformers causing them to explode oil over an area greater than any bund could catch. Again, the root cause is now well understood. A lightning induced flash over on the HV bushing causes the transformer tank to rise to more than 50kV. However, the LV winding is earthed separately from the HV earth and so the tank back flashes to the LV windings which fails resulting in a permanent LV side fault and transformer burnout. A simple 6kV lightning arrester fitted between the LV neutral and tank combined with a specified LV BIL (Basic Impulse Level) of 30 kV eliminates the problem. Also attention to LV fuse sizes and LV network look impedance significantly reduces burnouts due to uncleared LV faults.

➡ James Hoare LHW Partnership (Electrical & Energy Engineers). Old school BS171 transformers are pretty robust – some of the not quite so robust welded fin units I’ve seen on PV farms built to a cost are showing plenty of rust / Galvanic corrosion? already – agree with earlier post “ build a bund” Many PV inverters are transformer less so some dc content – will be interesting over the years the impact

➡ Matthew Pilgrim Senior Consultant Engineer (FM Global). Carl, in general transformer bunding is a good idea, but can be a costly exercise for existing installations. Factors to consider are: the cost and lead time of the transformer, its impact on production, whether an oil fire would expose adjacent transformers or buildings and the type of oil used (mineral oil, natural or synthetic esters). Environmental impacts are also important. FM Global has a fairly comprehensive standard on transformer installations that you can freely download from our website.

➡ Philip Fenwick Contract manager (Qualified). Carl, I except your answer and better knowledge but one would still think/conceder it a possibility to use the heat given off of the generator to give a start to warming water prior to going into a boiler making it cost less to bring the water to the temperature required, I just think in these times when we are trying to save energy and make things more cost effective it could be looked at.

➡ (Richard Emery IEng MIET MIHEEM Authorising Engineer (E) IHEEM AE(E) at Green Building Design Consultants). I get the transformer bunding problem, and even if you don’t have an oil storage problem, and the environment agency have incorrect information there is the risk assessment? Is a spillage going to cause secondary contamination, disruption and damage? How do we deal with external transformers/ bunding and rain water? I have seen some bunded walls with 300mm of water in them others with drain taps left on.

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➡ Carl A. Watkin Neil, can you directly replace oil with MIDEL, one for one? I was told by Schneider that retrofit would involve fitting larger rads to the transformer as the volume of Midel required, per transformer KVA unit, to achieve the same cooling properties was higher?

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➡ Graham White Founder (Power Balancing Services). I think one other point that relates to PAH is the need for a thorough maintenance programme including annual oil sampling. My experience in the embedded power generation world is that transformer maintenance is very poor. My view is that without a thorough maintenance programme you have more than an environmental issue, you have a serious H&S issue. In short don’t let PAH build up in the oil.

Whether you are an end user, Electrical Engineering Company, Facilities Manager or Senior Authorised Person, Eden will be able to assist you in the testing and maintenance of your liquid insulated electrical equipment for LV (Low), MV (Medium) and HV (High Voltage) applications up to 66kV.

➡ Neil Denbow (Director at Eden Transformer Oil). BS EN 61936-1:2010 species the options available eg two transformers can share one bund.

➡ James Hoare (LHW Partnership – Electrical & Energy Engineers). I thought the only way to get round was outdoor enclosure with class C or cast resin – when cast resin were first coming in they were welcome in buildings as an alternative to MIDEL as no need to bund the transformer.

➡ Neil Denbow (Director at Eden Transformer Oil). James, Class K insulating liquids such as the MIDEL range have the higher fire protection and are also readily biodegradable (unlike oil). However BS EN 61936-1:2010 doesn’t distinguish between the different liquids. By the way, as MIDEL Service Partners, we offer a mineral oil to MIDEL 7131 retrofill service. Click here for more information.

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➡ Carl A. Watkin. Philip, they don’t get that hot in normal use so heat recovery would be minimal (not like a CHP unit), but that’s not to say it could never be considered for some application.

➡ James Hoare LHW Partnership (Electrical & Energy Engineers). What a great idea !! I Infra Red tested a Cast resin Tx on a PV farm  in December and core was 85oC. I think this was made pre the EU directive on losses coming into force, but I do Heat pump work  and is a valid innovation as the conversion ratio of a GSHP is 3 to 4, so as the core losses are 24/7 and in a demand  location, heat of 60ºC could probably be efficiently collected by extracting 20ºC heat via a heat exchanger and efficiency would improve the hotter the oil temp . The Fe/core loss will be mainly heat, so what a great way to recycle the lost energy. Assume a flow and return input / output on transformer tank and a pump  to Heat pump compressor unit.  I think justifying costs would be the hurdle as a bit niche, and amorphous core transformers are getting cheaper and cheaper so the market is probably better for retro.

➡ James Hoare LHW Partnership (Electrical & Energy Engineers). Most pole mounts historically are DNO owned and there is DNO fuse protection on DNO point of connection with customer – largest pole mount in Uk is 315 KVA?

➡ Dan James Technical Services Engineer (HV Senior Authorised Person at NG Bailey) Richard, it also aids insulation, soaking into the craft paper and filling air gaps

➡ David Davenport CEng. MIET Technical Sales/Field Consultant/Advisor (Critical Energy Management, Switchgear, Protection and Control). Of course not to be confused, ( as many do) with instrumentation, metering and/or protection VT’s which ‘should’ if designed and built correctly remain at ambient temperatures, ( unless under fault conditions) Work as well in oil or cast resin insulate material. Cast resin though can significantly reduce insurance premiums, so much so, some companies have replaced old oil VT’s to cast resin and this has been paid for with the first years premium reduction. More info available if you message me?

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Thorne & Derrick can provide design and manufacturing services for Transformer Bunds with optional oil filters, drain valves, filter systems and ancillaries in both mild and galvanised steel (painted or unpainted) – innovative, efficient, safe and cost-effective solution for protection against leakages of insulating liquid to BS EN 61936-1:2010.

➡ Damian Flood FES (ABB Ltd). Well good practice would be to always bund an oil filled transformer. I would always recommend using a transformer oil with higher flash point Midel or FR3 also where the budget allows.

What are your thoughts on bunding, or not, of oil filled transformers? What criteria would you use to assess whether to bund, or not?

➡ Graham WhiteFounder (Power Balancing Services). This should answer the question. https://www.gov.uk/guidance/storing-oil-at-a-home-or-business#generators-and-transformers

➡ Craig O’Neill #e5 supporter, Technical Director at Completely Electrical UK and Electrical Trainer (Steve Willis training Ltd). That’s how I was taught! Belts and braces essentially because cleaning it up is something noone wants at all!!! Mega pricey nowadays.

➡ Manuel Bolotinha (Electrical Engineer). Usually sealed distribution transformers up to 630-800 kVA don’t need to be bunded.

Carl has over 40 years experience as a Projects Director, Electrical Engineer & Project Manager in the highly regulated HSE HID hazardous and heavy industry sectors – this includes global ATEX and IECEx hazardous environment and area industries, civil tunnelling, LV MV HV utility sectors and the renewables sector.

➡ Rob Lamb HV Field Engineer (UK Power Networks). Benjamin, I think they are looking at the possibility of directing fixed extinguishing systems at the transformer bund area where the fire would be centralised.

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➡ Paddy G. (Experienced Electrican trainee #e5 currently at PMck Electrical Ltd at PMcK Ltd). Hi Carl why are they oil filled ?

➡ Neil Denbow (Director at Eden Transformer Oil). Graham, that is the web page that the Environment Agency has confirmed will be corrected to match British Standards. So far it has only taken them one year.

➡ Nick Hill, MIET  Senior Authorised Person (SAP) / Service Engineer at ABB BS7671 only covers 1000v ac. So effectively half the transformer needs to be bunded. The HV side can do what it wants 😂

➡ Dan James Technical Services Engineer (HV Senior Authorised Person at NG Bailey). We’ve put in from full on concrete swimming pools, active filters to perspex shields around the rads to stop fluid spraying past the bund. Most of the time midel is used these days which doesn’t have the same environmental issues, a bund with a filter seems to be what we do most though.

➡ James Hoare (LHW Partnership – Electrical & Energy Engineers). Neil – thank you – I used to work for GEC many …moons ago and we used to make distribution transformers dry and liquid – in those days Midel was a GEC group company so know it well . GEC became Alstom and think it’s now Schneider at this volts !!!

➡ Dale Smallshaw Managing Director (CRITICAL ELECTRICAL SOLUTIONS LIMITED) There’s a regulation in the 18th edition where it covers transformers containing oil shall be bunded or pitted to distinguish any potential fires