Preliminary assessment of the technical condition of the power transformer based on regular oil testing

Preliminary assessment of the technical condition of the power transformer based on regular oil testing

The reliability of power transformers is crucial in the context of power system operation; the unplanned long-term shutdown of a single unit may result in both technical and economic consequences

1. Introduction

The reliability of power transformers is crucial in the context of power system operation. The distribution companies usually manage the fleets of hundreds of power transformers which is the reason why worldwide research is being regularly carried out addressing their reliability [1]. The unplanned long-term shutdown of a single unit may result in both technical and economic consequences.

The condition assessment of the transformer is mainly based on periodical tests [2, 3]. The advanced methods are used only in the case of emergency events, monitoring defect development or when determining the unit’s operating prospects. The unavailability of regular comprehensive diagnostic data means that the assessment of the general condition of the transformer is mainly based on the results of oil tests.

The data gathered during periodical tests and acquired in the process of continuous online measurements can be presented in the form of a single numerical indicator – the health index

The introduction of online monitoring systems has created a new quality in the assessment of the transformer’s technical state. The data gathered during periodical tests and acquired in the process of continuous online measurements can be synthetically presented in the form of a single numerical indicator, also known as the health index. This form is much more understandable at the level of company asset management and simplifies the comparison of transformers with different parameters. The application of the health index has been the subject of several different studies in recent years [4, 5].

The scientific-industrial consortium between Energo-Complex Ltd. and West Pomeranian University of Technology has established projects concerning the creation of new methods of transformer assessment and the prediction of future exploitation prospects [6]. One such project is the development of a health index algorithm based on the national operational and service experience, which aims to simplify the assessment by aggregating the most common measurement data.

Lead: A presented new algorithm for health index estimation was developed and tested on a fleet of 96 transformers with different operating settings to assess their general condition

This paper presents the health index based on the results of periodically performed advanced oil diagnostics.  The non-complex acquisition of the oil samples and the relatively low cost of performing such procedures creates a condition for a frequent calculation of the transformer’s overall health state. The presented algorithm was tested on a fleet of 96 transformers with different operating settings to primarily assess their general condition. The results were then compared to the expert reports regarding the technical condition carried out with the application of much more advanced measurement methods.

 

Vol. 7 Issue 4