Research on the characteristic parameter analysis and monitoring method of dry-type reactor turn-to-turn insulation degradation

One of the main causes of dry-type reactor failures is turn-to-turn short-circuit faults, where the operational safety of the equipment is greatly influenced by the condition of the turn-to-turn insulation. We thoroughly examine the evolutionary trends of important parameters such as winding current, short-circuit ring current and voltage, equivalent impedance, and winding phase angle during the insulation deterioration process using simulated turn-to-turn insulation degradation. We find winding current and equivalent impedance change is less than 15 % when insulation deteriorates; short-circuit ring current changes significantly but is hard to observe in practice; phase angle changes sharply and readily; the critical resistance thresholds for insulation degradation and total failure are determined to be 1000mΩ and 10mΩ, respectively; the phase angle change rate (x) is a useful indicator: x < 20 % denotes normal insulation, 20 %≤x < 100 % indicates continuous degradation, and x ≥ 100 % indicates insulation failure. Leveraging these findings, a novel monitoring method utilizing the winding phase angle change rate was proposed, and its feasibility was experimentally validated. Compared with conventional approaches, the proposed method demonstrates a 300 % sensitivity enhancement.