Case Terrafame
Mineral and chemical production
Inhibitor addition increases operational reliability and environmental savings
Case Terrafame battery chemicals production
Addition of the inhibitor to transformer oil in power transformers extends the lifetime of the transformers and transformer oil.
Background
Terrafame Oy's annual transformer oil analysis includes also measurement of the inhibitor content of the transformer oil in accordance with good maintenance practice. In two power transformers, the inhibit concentration founded to be below the recommended limit according to the IEC60422 standard. As a maintenance measure, it was decided to add an inhibitor to these two main transformers.
New transformer oil contains standardized amount over 3000 ppm of phenolic inhibitor (e.g., IEC60422). In the natural oxidation reaction of oil, heat and oxygen reacts with oil molecules, forming oil degradation products, causing, for example, the deterioration of the insulating properties of transformer oil. The inhibitor prevents this process by reacting with oxygen, protecting the oil molecule before the deterioration of the specific properties of the transformer oil and at the same time enabling an almost infinitely long lifespan of the oil.
The inhibitor chemical used to slow down the natural oxidation process may vary, but it is most commonly a phenolic antioxidant, which is commonly applied in all mineral oil-based insulating, lubricating, and hydraulic oils.
Pre-preparation includes planning, verification and research
Terrafame Oy's Factory Services' electrical automation maintenance team ordered Fluid Intelligence Oy to add the inhibitor during a maintenance break in spring 2023. The maintenance break was enabled by production shutdown when the transformers could be de-energized but only for maximum of 36 hours providing tight implementation schedule.
The addition of the inhibitor to the transformer oil is done by adding pre-treated inhibitor-containing transformer oil to the transformer. If necessary, some amount of oil in use is removed from the transformer to make room for the new oil. The practical work phases of the project must be prepared and planned in detail to ensure successful implementation.
In the project preparation, it was ensured that the general condition of the transformer oil was suitable for the addition of the inhibitor. In practice, the most important factors were a sufficiently low varnish content of the oil and, in general, the dryness and cleanliness of the oil. In practical planning and preparation, the resources and permits required for the project were reserved.
Addition of inhibitor to the transformer in practice
Picture 1. Terrafame power transformer
The implementation of the project began when the transformers were de-energized and safe working was possible. In the first phase, the oil handling equipment and supplies were positioned at the site and the necessary power supply was arranged for the limited operating area.
New inhibitor-treated oil was added to the transformers in a calculated amount exceeding the lower limit but not exceeding the recommended maximum concentration. The oil transfers were carried out with a dehydrating oil filter, ensuring that the moisture content of the new added oil was well below the recommended maximum limit. When the inhibitor addition was completed, the transformer oil was circulated with an oil dryer to ensure that the inhibitor mixed perfectly throughout the entire transformer oil volume.
The achieved increase of inhibitor content should be verified
Senior Development Engineer Veli-Pekka Kinnunen from Terrafame Oy's Factory Services' electrical automation maintenance team remarked: "The inhibitor content of transformer oil is an important part of the maintenance of oil-cooled transformers and is a cost-effective way to ensure the long lifespan of the transformer too. Alongside to operational reliability and cost savings, the addition of the inhibitor also enables clear environmental benefits when oil does not need to be changed unnecessarily. The project implemented by Fluid Intelligence Oy was a well-managed and overall professional package."
“In general, the implementation of the project was relatively simple, but due to the extremely limited time window, smooth implementation required good proactive preparation and precise planning”, says Mikko Oksanen from Fluid Intelligence Oy.
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Reducing oil consumption is an important step for the environment. Traditional mineral oil is a non-renewable natural resource, so every liter not changed is an environmental action. By utilizing existing investments and resources wisely, significant savings can be achieved.