Definite-time overcurrent protection scheme for floating crane supply system based on the instantaneous frequency characteristics of currents
The floating crane supply system usually incorporates large-capacity multiple asynchronous motors.During the starting process of these motors,simultaneous activation can result in substantial current surges.Consequently,the transformer bears a heavy current burden,potentially triggering the false overcurrent protection and leading to further industrial production losses.This paper investigates a protection scheme for transformers supplying multiple high-capacity motors.Firstly,the mechanism of the overcurrent during motor starting is analyzed by an equivalent model.Subsequently,a random scenario generating algorithm is proposed to generate a large number of scenarios for analysis.Furthermore,the Hilbert-Huang transform technique is employed to examine the time-frequency domain characteristics of both fault current and normal current,leading to improvements in the conventional overcurrent protection scheme.Finally,The effectiveness of the proposed protection scheme is validated through a realistic floating crane supply project in Hunan province.
definite-time overcurrent protectionHilbert-Huang transformcurrent instantaneous frequency characteristicsasynchronous motor startingintermittent periodic duty