On load tap-changer conditioned based maintenance

Recent years have witnessed a strong trend in electrical supply undertakings to enhance the quality of supply and at the same time to reduce operating costs. One means of achieving this is to improve the effectiveness of maintenance strategies. The paper examines the routine maintenance strategies of power transformers' on-load tap-changers and introduces new regimes which match the period between visits to the duty of the equipment. Hitherto the maintenance has been period-based with conservative intervals to preclude failure. The paper describes a condition-based maintenance strategy. Applying this to utility tap-changers has resulted in the maintenance intervals frequently being more than doubled. Thus maintenance costs are halved and system reliability is improved by targeting those units in need of attention and by avoiding spurious outages.