Flow electrification in power transformers: temperature influence on space charge distribution and charge accumulation in pressboard

Electrical-Based Diagnostic Techniques for Assessing Insulation Condition in Aged Transformers

“…Some experimental measurements have reported that the overall flow electrification increases with temperature to a certain limit situated between 40 • C and 60 • C before decreasing [19]. Mas et al [14], have shown that the temperature gradient influences the magnitude of the charge accumulated in the pressboard, but not the depth of the charge penetration. Oommen and Petrie [20], have reported that the electrostatic charge tendency of oil increases when the moisture content of the oil decreases.…”

“…During its motion, the oil acquires a positive or negative charge depending on the surface over which it travels [12,13]. If relaxation does not eliminate oil charges, and the charge accumulation at the insulating surfaces is high, static electrical fields can be produced, which may end in a static electrical discharge [12,14]. The combination of this static charge with impulse and switching surges may produce localized stresses of sufficient magnitude that they can initiate a catastrophic transformer failure [10].…”

Tracking and surface discharge at the oilߝpressboard interface

“…The oil relaxes the charge as it approaches earthed surfaces. If the relaxation does not eliminate charge quickly enough, a static electrical field can be established, which may end in a static electrical discharge [19], [20]. This phenomenon has been reported as a significant factor in some transformer failures [3], [16], [21].…”

Ação adsorvente da bauxita sobre óleo isolante novo

“…Devido à importância desses aparelhos elétricos, tanto a nível econômico como social, existem vários estudos no sentido de compreender os mecanismos de degradação do óleo 4,10,12,13,17,20,21 e da celulose do papel de isolamento 3,5-10,15,22 a fim de identificar os diversos tipos de falhas que ocorrem em um transformador durante o serviço. Da mesma forma, diversos trabalhos já foram realizados com o intuito de desenvolver sensores capazes de monitorar a qualidade do óleo isolante in situ para prevenir danos maiores 23 .…”