Monitoring and diagnostic of transformer solid insulation

Abstract

Abstract-Liberalization of the energy market has put increasing pressure on both electricity producers and distributors for lower costs. Since maintenance is a major expense account, such companies will be inclined to reduce maintenance budgets. At the same time, increased liability for non-delivered-energy increases the costs of sudden failure of a component. Transformers are such a component; they are often an essential link in the distribution network.In order to reconcile both decreasing maintenance spending and reliable service, condition-based maintenance (CBM) is often proposed. The basis of a successful application of CBM lies in obtaining information on transformers, so that, on the one hand, a critical condition will be noted early enough to take measures and, on the other hand, so that only minimal maintenance is being applied to transformers still in good condition. This paper will review a series of often mentioned techniques in order to assess what the value of this technique will be for CBM and whether it can be used for condition monitoring.

Raman Spectral Characteristics of Oil-Paper Insulation and Its Application to Ageing Stage Assessment of Oil-Immersed Transformers

“…In this study, the penalty parameter C and the kernel function parameters γ for SVM can be optimized by a genetic algorithm [40]. After being trained with the feature quality of the historic training data, the best parameters C and γ for SVM can be determined.…”

“…According to the guide for the diagnosis of insulation aging in oil-immersed power transformers [39,40], the five training classes of the clustering results in Figure 7a represented five aging stages: fresh condition (DP > 800), early age (500 < DP < 800), medium age (250 < DP < 500), late age (150 < DP < 250) and terminal age (DP < 150). Figure 7b illustrated the utility of the first three PCs for the classification of the training samples.…”

“…Finally, the 160 samples were placed in aging ovens and heated to 120 • C for the accelerated thermal aging of up to 160 days. Twenty samples were collected in days 1,10,20,40,70,102,110, and 160 to obtain oil-paper insulation samples with different aging states.…”

Surface-time enlargement law for gas breakdown

“…Previous verifications of the surface enlargement law provided satisfactory results in case of reversible insulation media (gas, vacuum, oil), as well as for the oil-paper insulation [4,5,[20][21][22]. Similar investigations on irreversible insulation media were inconclusive, owing to the impossibility of forming a representative sample of the breakdown voltage random variable for a solid insulator, since it is difficult to obtain a large number of identical solid-state laboratory specimen [23,24].…”

A Study on Deterioration Evaluation Method by Condition Monitoring and Diagnosis for Aging Oil-immersed Power Transformers

“…변압기의 과부하운전이나 비정현파 부하, 높은 주위 온도 등에 의한 비정상적인 운전 조건으로 최고 점 온도는 증가하게 되고 이것은 결국 변압기 수명을 단축 시키는 원인이 된다. 최고점 온도는 절연수명에 영향을 미 치며[8,9,10] "IEC 60076-7Table B.2 Temperatures at the end of each load step"을 이용하여 계산할 수 있다.…”