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  • M. Duval
  • IEEE Electrical Insulation Magazine
  • 1989
The use of dissolved gas analysis (DGA) to monitor the in-service behavior of transformers is discussed. Sampling techniques are briefly considered, and two commercial hydrogen-in-oil detectors are described. The first allows the hydrogen concentration to be measured at intervals of a few hours by a portable gas collector that can be connected to(More)
Dissolved gas analysis (DGA) is widely used to detect incipient faults in oil-filled electrical equipment. There is always some degree of inaccuracy in laboratory dissolved-gas measurements, especially at low gas concentrations, which affects gas ratios and other diagnostic calculations. This paper examines the measurement inaccuracy problem in detail using(More)
  • M. Duval
  • IEEE Electrical Insulation Magazine
  • 2008
Methods are presented in this paper allowing individual networks or transformer users to calculate their own specific DGA gas limits and required sampling intervals as a function of gas concentrations and rates of gas increase in service. This calculation can be done on the entire transformer population or on more specific segments of it. The purpose of(More)
Growing interest in optical instruments for biomedical applications has increased the use of optically calibrated phantoms. Often associated with tissue modeling, phantoms allow the characterization of optical devices for clinical purposes. Fluorescent gel phantoms have been developed, mimicking optical properties of healthy and tumorous brain tissues.(More)
A new monitor of hydrogen gas dissolved in transformer oil is described and tested under different conditions. Hydrogen diffuses from the oil through a permeable membrane into the monitor and reacts electrochemically with oxygen from the ambiant air in a fuel cell type arrangement. The monitor can be installed on a transformer for in-service continuous(More)
The causes of a number of explosions of EHV current transformers in service on the Hydro-Qu6bec 765 kV network have been investigated. Thermal runaway related to unexpectedly high dielectric losses in one of the types of oils used was diagnosed. Electrical instability of the oil was related to dissolved-meta content rather than to conventional oxidation of(More)
A new method for the characterization of electrical insulating oils, which employs the recently-developed technique of high-performance liquid chromatography, is presented. The method is simple and rapid. It provides "fingerprints" of oils, with information about their molecular size distribution, aromatic types and their degree of alkylation. These(More)
An oil additive of the blowing-agent type, which decomposes rapidly above 132°C with accelerated gas evolution at a concentration of 1000 ppm in oil, has been used to determine the hot-spot temperature during overload tests on a 16 MVA power transformer. The formation of gas in the Buchholz relay indicates that this e ottest-oil temperature of 132 ± 2°C has(More)
Transformer oils used in the northern part of the United States and Canada must have low pour-point temperatures in order to maintain good flow characteristics under the sometimes arctic conditions encountered during the winter months. The naphthenic oils presently used meet this requirement, but they are not expected to be available any longer, as the(More)