Flow Electrification In Transformers Research Articles

Summary on Mechanism of Oil Flow Electrification in Power Transformers

The mechanism of oil flow electrification in transformers was described in this paper. The mechanism of oil flow electrification in transformers could be understood from the effect of the oil flow’s movement and the electromotive action of AC electric field. The electric polarity of oil flow and the insulating layer were mainly depended on the state of charged cations and anions in oil, while the surface characteristics of solid materials only played a supporting adsorption role.

Physicochemical Analysis at the Interface Between Conductive Solid and Dielectric Liquid for Flow Electrification Phenomenon

At the solid-liquid interface, a charge zone called the electrical double layer (EDL) appears. It is constituted of two zones of opposite sign: one in the solid and another one in the liquid. When a liquid flows through a pipe, an axial streaming current is generated. This current is due to the convection of the charges coming from the EDL. The physicochemical reaction at the solid-liquid interface is one of the most important parameters which control the diffuse layer development inside the liquid and, consequently, the space charge density. In this paper, we present an analysis for the physicochemical reaction in the case of liquid containing additives or impurities partially dissociated into positive and negative ions. The addition of impurities, in our case, is associated with changing both the polarity and the value of the streaming current. Thus, from this difference in streaming current, we will be able to identify the reagent of the oil with the solid material. Furthermore, the effect of streaming potential on the EDL has been undertaken. Moreover, the fully developed space charge density at the wall is calculated with the help of streaming electrification experiments which are conducted in the case of nonfully developed EDL. This procedure can be conducted for the investigation of flow electrification in transformers with oil/metal configurations.

Flow electrification in transformers: relevance of ECT and leakage current measurements

The accumulated charge Q on a well insulated pressboard part being probably the most relevant parameter for flow electrification evolution inside transformers but clearly not measurable in situ, we compare in this paper this parameter with others possible to measure. The two most commonly used are oil parameters: ECT (electrostatic charging tendency) and, to a smaller extent, the continuous aging test for tan /spl delta/. Another is not so often used because of measurements difficulties, but was considered to be one of the most relevant: the leakage current. Thus in this paper we compare on two facilities (specially made for that) the accumulated charge Q to the ECT and leakage current. We find that, even if sometimes a correct correlation exists between these parameters, several cases show a bad correlation. Thus monitoring transformers by analyzing only ECT or leakage current seems to be hazardous.