船舶电网方向保护配置的研究

Research on Directional Protection for Ship Power Grid

船舶电网任意点短路故障时,电动机支路在短时间内会转变成发电机运行状态向短路点馈送短路电流。从电网方向保护的基本原理出发,分析了船舶的短路工况及电动机馈送短路电流,研究电动机馈送电流对电动机支路出口自身过电流保护的影响。结果表明,短路暂态过程中大容量电动机馈送的短路电流能达到额定电流的10倍,且随电动机容量的增大,馈送电流也相应增大,易造成电动机支路出口的过电流保护误动作。提出了在大容量电动机支路安装功率方向元件的措施,为船舶电网的安全运行提供保障。

Electric motor will run into a generator when ship power grid has short circuit faults at any point and will feedback short circuit current to the fault point. Based on the basic principle of directional protection, this paper analyzes the short circuit condition of ship and the feedback short circuit current of electric motor. The results show that during the transient process the short circuit feedback current provided by large capacity motor can reach 10 times rated current, and feedback current increases with the growing capacity of electric motor. The over-current relay protection at the branch export may be unwanted operation. On the basis of this conclusion, in order to distinguish the fault direction and guarantee the ship grid＇s safe operation, we propose some recommendations for power directional relay installation in motor branch.