Vegetable and seed oils are increasingly being used to insulate electrical transmission equipment. The IEC provides the standards for these environmentally friendly insulating liquids.
In developed nations, electricity is used without even thinking of it. It is employed for virtually every single action, from to switching the lights on in the morning to watching television in the evening, before setting the alarm for the next day. It is one of the features of the all-electric and connected society: the assumption that electricity will always be there to meet every need. But in order for that to happen, many people working in utilities and industry, right down to the electrician who lives next door, have to make sure that numerous safety and performance standards are met – and most of them are published by the IEC.
Such a carefree attitude to electricity does not exist in emerging nations, where people are more conscious of its benefits. But as electric power becomes more widely used across the globe, with people gaining access to a resource they previously had to do without, IEC safety and performance standards are just as essential.
Safety through liquid insulation
One of the areas that rarely makes the headlines but which is nevertheless essential for our safety is ensuring that the electricity transmission network is properly insulated. All electrical equipment has to be protected with a non-conductive material or substance that resists the flow of electric current and prevents short circuits and electric shocks.
Liquid insulation is one of the ways of ensuring transformers – which convert electric power from high voltages to lower voltages – remain safe. Liquid is used because of its cooling effect, which is essential for the energy-efficient operation of the equipment, enabling it to last longer. It is estimated that several billion L of insulating liquids are used in transformers worldwide.
Insulating liquids have been employed since the early 1900s when electricity started to be used. According to this article in ResearchGate, petroleum-based oil, so-called mineral oil, has been the main insulating liquid in industrial power systems since those early days because of its good aging behavior, low viscosity, ready availability and low cost. Crude oil was discovered in the mid-1800s and only slightly preceded the advent of electricity.
However, even in those early days, some of the inconveniences of mineral oils were already apparent. They were highly flammable and turned out to be dangerous to use in locations where fires could easily break out. The industry then started using polychlorinated biphenyl (PCB)-based insulating liquids from the 1930s onwards. However, PCBs are toxic and persistent chemicals.
According to the Communications Workers of America trade union, which represents workers who may come into contact with these chemicals, PCBs are not biodegradable, meaning they do not break up or separate into chemical arrangements, and may cause cancer and other serious health problems for humans and animals exposed to it, as well as provoking significant environmental contamination/pollution.
PCBs have thus been banned for use in most countries – they were phased out in the late ’70s-early ’80s in the EU – but still exist in transformers that were using them before they were banned. According to the Chair of the IEC technical committee which standardizes insulation liquids for electrical equipment, Ivanka Atanasova-Hoehlein, “There are ongoing efforts in many countries to identify and safely dispose of PCB-containing equipment.”
Moving to environmentally acceptable liquids
The desire to use safer and more environmentally friendly liquids has driven scientists to elaborate alternative solutions – a move which has accelerated over the last 40 years, as populations have become ever more aware of pollution risks and how to preserve the environment.
Global market research company MRFR estimates that the bio-based transformer oil industry, currently worth around USD 1,6 billion, is projected to grow by 7,3% by 2032. Bio-based fuels represent around a 35 % share of the market currently.
Sustainable, renewable, biodegradable and environmentally friendly insulating substances are used, although their cost remains higher than conventional liquids. Alternatives to mineral oils include vegetable or seed oils which are bio-degradable and much less toxic for the environment. They have some drawbacks, according to this research, notably being more vulnerable to oxidation.
Synthetic esters are also an option, as they are also biodegradable and do not emit polluting gases when burning. Atanasova-Hoehlein says they also “have a good oxidation stability, which allows for their use in equipment like traction transformers for railway systems”. They have disadvantages too as they are more costly than vegetable and seed oils, and are derived from petroleum sources, meaning they have a higher carbon production footprint.
Other alternatives include bio-based hydrocarbon, derived from biogenic waste, and gas-to-liquid (GTL) insulating liquids. “These belong to the group of unused mineral oils, as specified in one of our standards,” Atanasova-Hoehlein describes. Another alternative is to recycle used mineral oils.
Standards are key for environmental and safety reasons
IEC 60296 is widely recognized as the standard governing the use of mineral oils for insulation, including bio-based hydrocarbon liquids, produced by gas-to-liquid processes. The latest edition of this standard was published in 2020 and it also deals with the recycling of those conventional oils. The IEC has issued most of the required safety and performance benchmarks in the area and is increasingly focusing on environmental requirements. Natural esters such as vegetable oils are standardized in IEC 62770, while synthetic ones are specified in IEC 61099, a third edition of which is currently under development.
As we move towards an all-electric world, insulating liquids are becoming more essential than ever before, while meeting increasingly stringent environmental targets, with the help of IEC Standards.
Author: Catherine Bischofberger
The International Electrotechnical Commission (IEC) is a global, not-for-profit membership organization that brings together 174 countries and coordinates the work of 30.000 experts globally. IEC International Standards and conformity assessment underpin international trade in electrical and electronic goods. They facilitate electricity access and verify the safety, performance and interoperability of electric and electronic devices and systems, including for example, consumer devices such as mobile phones or refrigerators, office and medical equipment, information technology, electricity generation, and much more.
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