Development of On-Line Monitoring Device for Interturn Short-Circuit of Dry-Type Air-Core Reactor Based on Star-Arm Current Change Rate

The dry-type air-core reactor often causes the coil to burn due to the interturn short-circuit during operation. The existing non-electrical quantity detection methods such as temperature and smoke, and the electrical quantity detection methods such as partial discharge are not real-time, accurate and sensitive enough, and cannot be warned in time. Therefore, this paper designs an on-line monitoring device for interturn short-circuit of dry-type aircore reactor based on star-arm current change rate. Firstly, the variation rule of star-arm current before and after interturn short-circuit of different types of air-core reactors is analyzed, and the criterion of interturn short-circuit is proposed. Then, based on the principle of electromagnetic induction, a star-shaped arm current self-powered power supply unit is designed to achieve a stable output of isolated $\pm$ 5 V DC voltage. In order to realize the synchronous acquisition and transmission of multi-star-arm current signals, a 4G wireless transmission unit is further constructed based on ZigBee networking technology, which solves the problem of wiring redundancy and signal interference caused by traditional wired data transmission. Finally, the 66 kV drytype air-core reactor is taken as the experimental object, and the interturn insulation test is carried out by using this system to simulate the interturn short-circuit defect. The experimental results show that the on-line monitoring device designed in this paper can accurately realize the diagnosis and early warning of interturn short-circuit of dry-type air-core reactor.