Comparative Analysis of the Results of Diagnostic Measurements with an Internal Inspection of Oil-Filled Power Transformers

Abstract

This article presents a description of four independent case studies concerning situations when power transformers were directed to internal inspection. This inspection was the result of a specific case of a routine diagnostic procedure that was carried out and, where the transformer was switched off by a Buchholz gas relay. The case studies described were selected such that they represented situations when availability of historical data on the previous measurements was limited and a quick diagnosis had to be made on the basis of the results from the last measurement. In all of the cases presented here, the analysis of the gases dissolved in oil had played an important role in the detection of the defects that turned out to be dangerous for further exploitation of the transformers considered. The first signal about a possible developing defect was elicited solely from the measurements of the oil samples taken from the transformer in service. However, more detailed recognition and initial localization of the defect was possible after additional supplementary measurements (winding resistance, sweep frequency response analysis, etc.), which required the transformer to be switched off. The conducted sequence of actions, based on the developed diagnostic procedure, indicated the possibility of effective and early withdrawal of the transformer from operation, before it underwent a serious failure.

Precise Measurements of the Temperature-Frequency Dependence of the Conductivity of Cellulose—Insulating Oil—Water Nanoparticles Composite

“…As a rule, in FDS alternating current tests, measurements are made at three points per decade [11,[50][51][52]. In this way, tests of power transformers have also been performed [53][54][55][56][57][58]. This is due to the very highly time-consuming characteristic of measurements at ultra-low frequencies.…”

Technical committees

“…Condition monitoring information of insulating oils will reveal the service behavior in various operating conditions. The members of the TC on Liquid dielectrics are also individually involved in collecting and analyzing the condition monitoring information of oil filled apparatus that belong to local utilities (as for example [1,2]). • Aging Phenomena: Insulating systems are generally designed to be in service for several decades and hence understanding the aging behavior is essential to attain the designed life of the apparatus.…”

Influence of ageing on oil degradation and gassing tendency under high‐energy electrical discharge faults for mineral oil and synthetic ester

“…Thus, careful monitoring of the degradation rate and appropriate condition monitoring actions are essential for the successful operation of the transformers. This allows the utility and engineers to meet the designed life while leading to efficient asset management [3, 4].…”