小波变换在全线相继速动保护中的应用

摘要

在线路距离保护Ⅱ段范围发生故障时，利用对侧开关跳闸时序电流的突变量加速本侧保护的跳闸，改善了保护的性能。这一相继速动原理曾在微机线路保护中得到应用，但在某些系统参数和故障类型下序电流的工频突变量微弱，判据灵敏度不足。文中提出了用双正交小波变换检测突变量的方法，以解决利用序电流作为突变量存在死区的问题。%This paper presents a novel approach to accelerated trip of power transmission lines by using biorthogonal wavelet transform to improve the performance of protection relays. The existing accelerated trip principle has been widely applied. However, a lower sensitivity has been observed for some special system parameters and fault types to which the second abrupt changes of sequence currents are especially faint. A wavelet decomposition algorithm is proposed in this paper, which possesses capabilities of fast calculation, partitioning the higher frequency band and linear phase. This algorithm provides an accelerated trip scheme, which can efficiently extract the faint second abrupt changes of currents and is able to deal with the dead-zone problem of conventional scheme. The simulation results of MATLAB/SIMULINK show its feasibility and efficiency.