بحث در مورد مشکل فوق انجام شده است و بنده چیز جدیدی به ذهنم نمی رسد. تنها نکته اینکه ستینگ پایداری در شرایط راه اندازی را چک نمائید. Starting ratio (S) Under ideal circumstances, and when there is no fault inside the protection zone, the differential current is zero. However, due to CT inaccuracies and varying tap changer positions (power transformer applications), the differential current deviates from zero in practice. An increasing the load current cause the differential current to grow at the same percentage rate. The starting ratio setting (S) affects the slope of the relay operating characteristics between the 1st (fixed 0.5 x In) and the 2nd turning-point (setting I2tp): an increase in the load current causes the differential current required for tripping to increase with the set percentage. The S setting is calculated as the sum of the accuracies of the CTs on both sides, the tap changer regulation range, the relay operation accuracy (4%) and the desired margin (typically 5%). 
Example The CT on both sides are rated 5P10 (i.e. the composite error is max. 5%) and the tap changer range is
