Looking after the grid

Operating 72,000 km of high voltage electricity lines is no small task, and high-quality transformer oils are vital for success.

Analysing the oil in a transformer is reminiscent of taking a blood sample. But in this case the objective is to assess the state of the transformer to prevent and identify risks of future problems.

If there was such as a thing as a transformer doctor, Fabio Scatiggio would certainly fit the job description. As the Chemical Laboratory Manager of Terna, Italy’s national electricity transmission company, he is in charge of analysing liquid, solid and gaseous insulating materials and transformer diagnostics.

“Terna’s main task is to transmit electricity from the power plants to the consumer at the lowest possible price. The most important part of our assets is the transformer. We operate 900 transformers throughout Italy, ranging from 50 to 400 KV.”

Fabio Scatiggio heads up a team of ten people who perform testing of every kind of insulating material in the transformer, from gas and metals to the important transformer oils. Although Terna buys limited amounts of insulating oil directly from the producer, they have very stringent specifications for the oil when they purchase new equipment.

“In some cases, we buy small amounts of insulating oil to top up. But the big volumes come with the transformer when it is delivered from the factory. This includes not only standard industry requirements, but also more specific ones such as recently introduced demands to reduce stray gassing,” he says.

“In the past we used uninhibited oils, but around ten years ago we changed the specifications to also accept fully inhibited high-grade oils.”

It is Terna's general practice to operate an oil-filled transformer for up to 40 years. So the fluid’s long-term performance for oxidation stability is crucial.

“For standard applications such as large power transmission transformers and reactors, we use high grade oils, but for critical applications – HV/DC or PST – our specifications are more stringent and only super grades are suitable,” notes Fabio Scatiggio. “Such extra performances encompass very low DDF and electrical conductivity, negligible ECT and non-gas-evolving attitude.”

Different grades of Nynas naphthenic insulating oils are found in 70-80% of Terna’s transformers. Fabio Scatiggio considers the company an important partner thanks to its expertise and position as a main player in supplying mineral technical oils.

“We have a long and very good working relationship. In addition to being an important player in the oil market, Nynas is also very active in international standardisation bodies, which means that we get together at various industry meetings and events throughout the world. I would also like to express my great appreciation for the important work and the support we receive from Nynas’ local office in Italy.”

The Italian representative in many IEC and CIGRE working groups, Fabio Scatiggio has published numerous papers on transformer diagnosis by dissolved gas analysis and on problems relating to the presence of corrosive sulphur in oil. He has also developed the so called HI (health index), which is a dashboard that receives many different inputs from the transformer and acts as a sort of traffic light on problems that can arise.

“Although budget restraints are making it increasingly difficult, I am convinced that participation in international bodies is vital for a company like Terna as well as the industry as a whole.”

Fabio Scatiggio has a positive outlook on the future for the industry, and also notes the high improvement in the quality of transformer oils in recent years as Nynas and other suppliers went over to hydrotreatment of the oils. “This was a very significant step forward, and the current products provide incomparable performance compared to those in the past.”