Study on turn-to-turn insulation fault condition monitoring method for dry-type air-core reactor

The change of current value caused by turn-to-turn insulation fault of dry-type air-core reactor is so little that the failure detection is difficult to be carried out. In order to solve this problem, a new monitoring method based on impedance variation is proposed in this paper. A circuit model of the dry-type air-core reactor turn-to-turn insulation fault is established and the numerical method is applied to analyze the variation of equivalent resistance and equivalent reactance when dry-type air-core reactor winding short circuit happens in different places. Based on this, the paper proposes to utilize voltage signals and current signals of dry-type air-core reactor and adopts the quasi-synchronization harmonic analysis algorithm to obtain the equivalent impedance. Then the insulation fault can be detected by the variation of impedance. All of the above are studied by testing. The research result shows that, the equivalent resistance increases and the equivalent reactance decreases when turn-to-turn short circuit occurs, and the variation of equivalent resistance is more obvious than equivalent reactance. Quasi-synchronization harmonic analysis algorithm has the features of strong anti-interference capacity and a high measuring accuracy, it can effectively identify the impedance change. The experiment results prove that this monitoring method is true and feasible.