Abstract
At a solid/liquid interface, physico-chemical phenomena occur that lead to the separation of electrical charges, establishing a zone called electrical double layer. The convection of one part of these charges by the liquid flow is the cause of the flow electrification phenomenon which is suspected of being responsible of incidents in the industry. The P' Institute of Poitiers University and CNRS has developed an original sensor called “capacitive sensor” that allows the characterization of the mechanisms involved in the generation, accumulation and transfer of charges. As an example, this sensor included in the design of high power transformers, could easily show the evolution of electrostatic charge generation developed during the operating time of the transformer and, therefore, point out the operations leading to electrostatic hazards and, then, monitor the transformer to prevent such risks.
Highlights
When a liquid is in contact with a solid, a physical chemical phenomenon creates a charge separation area called the ―electric double layer‖ which polarizes the solid/liquid interface
The results showed that the space charge density was multiplied by three or four when the pressboard had been degraded by electrical discharges
This sensor is based on the accident analyses in high power transformers in which electric discharges were observed on pressboard surfaces in very well insulated parts of transformers
Summary
When a liquid is in contact with a solid, a physical chemical phenomenon creates a charge separation area called the ―electric double layer‖ which polarizes the solid/liquid interface. Charged species of one sign appear on the solid surface while species of the opposite sign are Sensors 2012, 12 distributed within the liquid These areas are responsible for electrokinetic phenomena including the phenomenon of flow electrification. The aging of power transformer components (pressboard, oil, copper...), due to temperature and moisture, influences the flow electrification phenomena. It seems that flow electrification might generate a surface charge, which would induce electrical discharges at the pressboard-oil interface enhancing the phenomenon. The results showed that the space charge density was multiplied by three or four when the pressboard had been degraded by electrical discharges This conclusion was alarming because it seemed that a chain reaction might happen inside the power transformer, until its failure [11]. This sensor is based on the accident analyses in high power transformers in which electric discharges were observed on pressboard surfaces in very well insulated parts of transformers
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