Dissolved Gas Analysis Methods Research Articles

Anusual Application of Partial Discharges to Diagnose of High Voltage Power Transformers

The article contains information on research carried out in Electric Faculty of Silesian University of Technology, made at test stations and aimed at diagnosis how is actual technical state of high voltage power oil transformers. Opinion on a state of transformers is based on analysis results of partial discharge measurements. Authors use simultaneously: electric, acoustic and dissolved gas analysis method. Applied acoustic method is the original own one. Non-conventional application of electric method is proposed, too. In the frame of chosen methodology the partial discharges are measured and next calculations of quantities describing partial discharges within particular methods are carried out in order to describe phenomena commonly for electric and acoustic method. Information sources about level and kind of partial discharges are measurement results obtained from electric method whereas information on places where partial discharges appear is contained in measurement results coming from acoustic method. Authors present selected application results of such a combined measuring method.

A study of the temperature-based dynamic nature of characteristic gases in oil-cellulose insulation systems

Dissolved gas analysis (DGA) is a well established method to monitor and predict the condition of devices with oil-cellulose insulation, especially power transformers. However, the effect of the migration of theses gases between the liquid and solid insulation is often ignored. The migration phenomenon is temperature dependent and, if ignored, can potentially lead to erroneous condition assessment by the DGA method. This paper addresses the dynamic nature of propagation of these gases in such systems based on temperature variations. Diffusion times, and therefore diffusivity of the gases, in oil-impregnated cellulose are calculated by identifying the diffusion process as a linear system. The diffusion time-constants, and steady-state condition at the working concentrations, are estimated based on the identified model. A sensitivity study is performed to show the dependency of the diffusion time-constants to the temperature and the oil-cellulose ratio in the system. The equilibrium curves are obtained in the case of carbon dioxide by using solubility information of this gas in the oil and paper pulp, similar to the case of moisture equilibrium. The results are compared with the experimental data. An example of the implication of the obtained data is shown

A fuzzy dissolved gas analysis method for the diagnosis of multiple incipient faults in a transformer

Dissolved gas analysis (DGA) of transformer oil has been one of the most useful techniques to detect the incipient faults. Various methods, such as the IEC codes, have been developed to interpret DGA results directly obtained from a chromatographer. Although these methods are widely used in the world, they sometimes fail to diagnose, especially when more than one fault exists in a transformer. This paper presents a fuzzy logic technique which can diagnose multiple faults in a transformer and quantitatively indicates the likelihood/severity of each fault. Insulation deterioration at each fault location can then be monitored closely according to its trend, which is important for a transformer in critical situation. Tests using this technique on a number of transformers have given promising results.