Fault Analysis and Resolution for a 35kV Dry-Type Air-core Reactor Incident

Dry-type air-core reactors are widely utilized for their structural and performance benefits. Nevertheless, as electric power systems evolve rapidly, there are increased expectations for reactors in terms of performance and quantity. This evolution has led to a rise in the incidence of safety accidents prompted by reactor malfunctions. In-depth understanding of these malfunction mechanisms is of paramount importance for enhancing manufacturing processes and ensuring the stability of the power grid. This paper presents an analysis and resolution of a fault incident pertaining to a 35kV reactor within a 220kV substation. The initial assessment based on site inspection suggested that the insulation breakdown of the coil encapsulation was the probable cause. The fault was confirmed to be an inter-turn short circuit within the reactor through a series of tests, including direct current (DC) resistance, inductance measurements, and inter-turn insulation testing. It is thus inferred that pre-existing insulation cracking or localized flaws, exacerbated by the conditions of dusty weather and cold waves, led to the insulation breakdown and consequent inter-turn short circuit. In light of these findings, the paper suggests implementing preventative measures such as regular inter-turn withstand voltage testing, endoscopic inspections, diligent air duct cleaning and maintenance, and infrared thermography, with the goal of mitigating the recurrence of similar faults.