考虑电流瞬时频率特性的水上浮吊供电系统定时限过流保护方法

Definite‑time overcurrent protection scheme for floating crane supply system based on the instantaneous frequency characteristics of currents

水上浮吊供电系统中,通常含有多台大功率异步电动机,多个电动机在并网启动时会产生较大的启动电流,当各电机启动电流叠加,可能导致变压器电流激增,触发过电流保护误动,给工业生产带来巨大损失。本文首先基于异步电动机等效模型,揭示了冲击电流的产生机理和箱式变压器保护误动原因;接着针对水上浮吊电机断续周期工作场景,提出了随机运行场景生成方法,基于希尔伯特黄变换技术,对系统的故障短路和电机启动状态下变压器的电流信号进行瞬时频率特性分析,揭示不同状态下箱式变压器电流的瞬时频率特性差异,在此基础上构建定时限过电流主动闭锁模块,确保浮吊供电系统正常工作时的可靠供电;最后通过湖南省某水上浮吊系统的仿真模型对所提出的保护方案进行了验证。

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 highcapacity 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.