Abstract: In the reactive power compensation system of the power grid, parallel capacitor banks are usually connected in series with dry-type air-core reactors to suppress harmonic amplification and reduce closing inrush current. However, the lack of effective protection methods in the event of inter-turn short circuits in the reactors leads to the failure being unable to be cut off in a timely manner until burnout. Due to the inter-turn short circuit of dry-type air-core reactors being an arcing short circuit, based on the periodic extinction reignition fault characteristics of the arcing short circuit between turns of the reactor, a model of arcing short circuit is constructed. The study is conducted based on the different inductance change rates caused by the short circuit. It is found that when the arcing short circuit occurred in the reactor, a specific number of harmonics will be excited in the fault phase, and the neutral point voltage of the parallel capacitor group containes significant harmonic voltage changes. Based on data analysis, a fault monitoring and protection method for inter-turn short circuits in reactors is proposed based on the content of harmonic voltage at the neutral point, combined with the characteristics of zero sequence voltage and fundamental voltage changes.