A preventive maintenance schedule consists of regular inspections and component replacements according to the product specific maintenance schedule. Maintenance schedules are based on Hitachi ABB Power Grids decade’s long experience of manufacturing and maintaining its products. Regular preventive maintenance helps facilitate forward budget planning.
The main point of concern in ageing and the life expectancy of transformers is the condition of the insulation system, which is typically based on organic products.
The organic products in a transformer degrade over time and finally they lose the capability to withstand the stresses a transformer might see in daily life (short circuits, energizing, vibration, etc.). It is possible to reverse the ageing of mineral oil through oil reclamation that can restore the material properties close to the values when new. Ageing of paper insulation however is an irreversible process and is considered one of the life-limiting processes of a transformer.
The lifetime of this combination of mineral oil and paper in a transformer is very much dependent on the operating temperature, oxygen content, acidity of the oil and the moisture content in the insulation. Temperature is mainly dependent on the transformer design, the loading, the cooling facilities, and the ambient temperature. Changing these parameters is not easy and normally involves large investments. Moisture is accumulated within the paper insulation of the transformer and has different sources.
To extend the life of your assets, Hitachi ABB Power Grids provides preventive (eventually curative) actions to be performed on-site aiming to maintain the performance of the transformer for which specific equipment and a higher degree of expertise is required. It is usually linked with diagnosis tests and possible engineering studies to clearly determine the most appropriate route of action and ensure a condition based maintenance.