Streaming electrification of mineral insulating oil and synthetic ester MIDEL 7131

Abstract

Determining the Electrostatic Charging Tendency (ECT) level of insulating liquids requires no large and therefore costly transformers or modelling systems. Small laboratory systems are characterised by simple design and methodology, low volume of liquid sample required for testing, low cost of construction and the following tests. This also applies to pipe flow systems. This paper presents comparative studies of the phenomenon of streaming electrification of mineral TRAFO EN insulating oil and MIDEL 7131 ® synthetic ester flowing through a pipe made of conventional cellulose paper and modern aramid paper. Electrification current vs. liquid flow speed was measured. The influence of pipe material was determined. Also the effect of temperature and sample aging time on the extent of the streaming electrification was studied. With the Abedian-Sonin model, volume density of the q w charge, which is a parameter describing ECT of insulating liquids, was determined.

Comparisons of streaming electrification characteristics between an ester liquid and a mineral oil using pipe flow method

“…It is evident that the ester liquid has a higher leakage current than the mineral oil. Similar findings have also been identified in previous studies [9][10][11]. The different streaming electrification characteristics of the two liquids have been linked to the differences in the liquids' chemistry [13].…”

“…Thus it is significant to study the streaming electrification behaviors of the ester liquids. Up to now, a few publications have revealed that the ester liquids generally have a higher electrostatic charging tendency than the mineral oil [9][10][11].…”

Research on the Relation between Transformer Oil Flow Electrification and Electrostatic Current

“…Combining with the comparative result between the calculated value of ρ (1) and the accumulated real value of ρ , the GM (0, 2) model of the electrification degree of oil flow and the electrostatic current could be initially expressed as in (5). The data of the electrification degree of the oil flow calculated from the linear regression model is also showed in Table 2.…”

“…The Electrification Degree of oil flow, namely the Charging Tendency, or Electrostatic Charging Tendency (ECT), represents the capability of generating electric charge when the transformer oil flows through the solid insulation surface under certain external conditions such as velocity of flow and pressure, and can be represented by charge density (ρ), which means the charge number generated from per unit volume of transformer oil: ρ= q/V (V is the total volume of transformer oil, and q is the total charge number generated when oil flows through the solid insulation surface). And we often use C/m 3 , pC/ml or pC/cm 3 as the unit of Electrification Degree [1][2][3][4][5][6]. Through researches, scholars from all over the world hold the opinion that the electrification of transformer oil flow has a lot to do with the insulation structure of the transformer, oil flow velocity, oil temperature and charging tendency (electrification degree) of oil flow.…”

Analysis of High-Frequency Dispersion Characteristics of Capacitance and Loss Factor of Aramid Paper Impregnated with Various Dielectric Liquids

“…Another action, which should be taken mainly by the users of such equipment, is proper operation supplemented with monitoring of the key apparatus of the system. In the case of power transformers, solid and liquid insulation, which so far has been made of cellulose impregnated with mineral insulating oil will be more often substituted with synthetic insulation, mostly made of aramid papers ultimately impregnated with environment-friendly synthetic and natural esters [1][2][3][4][5][6]. Compared with cellulose, the application of aramids causes a significant increase in the resistance to high temperatures, which is presently the main factor having influence on premature aging of insulation [2,[6][7][8].…”