三相输电系统中能流的可视化与机制特征

Visualization and Mechanism Feature of Energy Flow Along Three-Phase Transmission System

提出了一种三相输电系统中能流的可视化方法。首先采用相电压和相电流描述三相输电线周围的电场强度和磁场强度,并用坡印亭(Poynting)矢量确定空间任意点的电磁能流密度。再将电磁能流的密度作为木质棒的密度,用质点的密和疏分别表示木质密度的大和小,从而将沿三相输电线传输的不可见电磁能流用可见的木质棒(简称能流棒)形象地展现出来。仿真结果和能流棒的图像表明,正弦稳态三相线路整体传输的电磁能流不含经典定义的无功成分,只由波动的入射能流和波动的反射能流组成,且这2部分均呈螺旋状传播。与电路理论相比,电磁场理论能更深刻地揭示三相输电系统中电磁能量流动的底层机制和特征。

A visualization method for the energy flow in three-phase power transmission system is proposed. Firstly, the electric field strength and magnetic field density surrounding three-phase transmission line are expressed by phase voltage and current, then the density of electro-magnetic energy flow at arbitrary spatial point is determined by Poynting vector; and then taking the density of electro-magnetic energy flow as the density of a wooden bar, the high and low extent of the wooden density are expressed by the dense and sparse extent of mass point, thus the invisible electro-magnetic energy flow along three-phase transmission line can be revealed by visible wooden bar （for short, the energy flow bar or EFB）. Results of digital simulation and the image of EFB show that the overall transmitted electro-magnetic energy flow along three-phase transmission line in sinusoidal and steady state does not have reactive component in classical definition, and it only consists of fluctuant incident and reflected energy flows, and both parts travel spirally. The electro-magnetic field theory can reveal the fundamental mechanism and feature of electro-magnetic energy flowing along three-phase power transmission system in depth.