Regular Article

Streamer evolution arrest governed amplified AC breakdown strength of graphene and CNT colloids

¹ Department of Mechanical Engineering, Indian Institute of Technology Ropar, Rupnagar 140001, India
² Department of Mechanical Engineering, State University of New York Binghamton, Binghamton, NY 13902, USA
³ Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600036, India

^* e-mail: purbarun@iitrpr.ac.in

Received: 18 December 2018
Received in final form: 1 February 2019
Accepted: 21 February 2019
Published online: 26 April 2019

Abstract

The present paper explores the concept of improving the AC dielectric breakdown strength of insulating mineral oils by the addition of graphene or carbon nanotubes (CNTs) to form stable dispersions. Experimental observations of graphene and CNT nano-oils show that not only improved average breakdown voltage, but also significantly improved reliability and survival probabilities of the oils under AC high voltage stressing is achieved. Improvement of the tune of ∼70–80% in the AC breakdown voltage of the oils has been obtained. The study examines the reliability of such nano-colloids using a two-parameter Weibull distribution and the oils show greatly augmented electric field bearing capacity. The fundamental mechanism responsible for such observed outcomes is reasoned to be delayed streamer development and reduced streamer growth rates due to effective electron scavenging. A mathematical model based on the principles of electron scavenging is proposed to quantify the amount of electrons scavenged by the nanostructures.