EFFECTIVE METHODS FOR POWER TRANSFORMERS CONDITION ASSESSMENT – A VIEW BASED ON PRACTICAL EXPERIENCE

Y.Aksenov, I.Yaroshenko (DIACS, Russia), A.Andreev (Union, Italy) G..Noe (Comelmar, Italy)

 

Abstract. Practical experience for 20 transformers is given in the paper. On-line monitoring (measuring certain parameters or conditions while energized) of transformers and associated accessories is an important consideration in their operation and maintenance. The justification for on-line monitoring is driven by the need to increase the availability of transformers, to facilitate the transition from time-based and/or operational-based maintenance to condition-based maintenance, to improve asset and life management, and to enhance failure cause analysis. There is a common tendency of moving from the time-based to the condition-based maintenance to reduce maintenance costs, to extend significantly the life span of equipment and, at the same time, to prevent possible catastrophic failures.

Main aspects of using Diagnostic Method Synergy are following:

  - Equipment durability can not be guaranteed by a single diagnosis carried out by one physical method. It can only be provided by multiple  diagnoses through various methods.

- Each type of the transformers element (windings, LTC, Bushing, Core, etc.) demands specific diagnostic methods, the choice of which should be determined by a compromise: on the one hand to enhance reliability we need to increase the number of the methods used, on the other hand to minimize the cost losses methods are desirable

Efficiency of the following diagnostic methods were substantiated:

- PD-activity on-line pinpointing with temporary outside electromagnet high frequency sensor system using;

- Infrared thermography;

- Transformer oil probe analysis of dissolved gases and furan components;

- PD and tgä monitoring.