Feasibility analysis of impedance monitoring method for turn-to-turn insulation fault of Dry-type Air-core Reactor

Dry-type Air-core Reactor consists of multi-layer coils and Multi-strand windings. The change of impedance value caused by turn-to-turn insulation fault of dry-type air-core reactor is so little that the over current protection and Three-phase imbalance protection can't act timely. In order to monitor turn- to-turn insulation fault of reactor, a new monitoring method based on impedance variation is proposed in this paper. Takes reactor BKK-20,000/63 for an example to study the relation between the variation of impedance value and the turn-to-turn insulation fault position of dry-type air-core reactor. The result shows that the change of equivalent reactance value caused by turn-to-turn insulation fault is little, while the change of equivalent resistance value is large. The closer the axial fault to both ends is, the larger the variation is. Along with the radial fault location, variation of outer is larger than inner's. Method based on the variation of resistance to monitor the turn-to-turn insulation fault of dry-type air-core reactor is feasible. Besides, the relative monitoring method based on loss or tangent of dielectric loss angle is reasonable.