➡ 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
Bunding – Oil Filled Transformers, To Bund or Not to Bund?
Published 25 Apr 2019
Transformer Bunds | Bunds for oil-filled transformers manufactured from steelwork on reduced lead time and at competitive prices from Thorne & Derrick | Contact us with your requirements | Stock, Service & Product Support
How Can We Help?
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.
BS EN 61936-1:2010
Power Installations Exceeding 1kV a.c. Common Rules
Oil Filled Transformers
Guest Contribution: Carl A. Watkin IMEMME (Hons) I.Eng MIMMM MIET AIOSH
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.
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.
Bunding – Oil Filled Transformers
To Bund or Not To Bund?
by Carl A. Watkin
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.
See: BundGuards | Substation & Transformer Oil Spills & Leaks Containment
What are your thoughts on bunding, or not, of oil filled transformers? What criteria would you use to assess whether to bund, or not?
➡ 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
Contact Applied Power Engineering
➡ Usually sealed distribution transformers up to 630-800 kVA don’t need to be bunded.
➡ 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.
➡ (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.
➡ 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.
➡ 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.
➡ 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.
➡ 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.
➡ 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.
➡
Contact Applied Power Engineering
➡
➡ 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
➡ There’s a regulation in the 18th edition where it covers transformers containing oil shall be bunded or pitted to distinguish any potential fires
➡ I would bund to 110per cent
➡ Neil Denbow (Director at Eden Transformer Oil). BS EN 61936-1:2010 species the options available eg two transformers can share one bund.
See: BundGuards | Substation & Transformer Oil Spills & Leaks Containment
Eden Transformer Oils
Eden Transformer Oil Ltd was formed by Alan Denbow and Eddie Gregory in August 1985.
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.
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.
Since August 1985 Eden have been testing and maintaining the insulating liquids in transformers and switchgear in the United Kingdom, Belgium, France and Germany.
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.
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.
➡ 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
➡ 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.
➡ 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.
➡ 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.
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.
➡
➡ 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.
➡ 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.
➡ 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.
➡ 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.
➡ 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.
➡ 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.
➡ 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?
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.
➡ Carl A. Watkin. If they are under specified Neil, they shouldn’t be installed, never mind bunded!
➡ Carl A. Watkin. Might double skinning then create over temperature problems Andy?
➡ This should answer the question. https://www.gov.uk/guidance/storing-oil-at-a-home-or-business#generators-and-transformers
➡ 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.
➡ 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
➡ Something regularly discussed within DNOs….
➡ 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.
➡ 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.
➡ 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.
➡ 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.
Visit: Applied Power Engineering
➡ 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.
➡ 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 !!!
➡ 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?