基于改进暂态能量方向的半波长输电线路保护方法

Half-wavelength transmission line protection method based on improved transient energy direction

针对传统特高压保护方法难以直接应用于特高压半波长交流输电系统的问题,提出基于改进暂态能量方向的半波长输电线路保护方法。半波长输电线路测量阻抗随故障位置不再呈现单一线性变化,导致传统距离保护不能直接应用于半波长输电线路,而行波在超长线路上衰减损耗极大,难以准确检测行波波头,故行波保护亦难以用于半波长输电线路保护。因此,提出一种基于改进暂态能量的方向保护方法,通过线路两端检测到的暂态电气量计算输电线路三相瞬时功率,并通过瞬时功率的积分求取暂态能量,以暂态能量的极性构造区内、区外故障判据。经大量仿真验证,无论故障点位于线路何处该方法均能够可靠实现区内、区外故障辨识,此外暂态能量极性不受故障角、过渡电阻改变而改变,所需采样率仅10 kHz,仿真结果证明该方法准确、可靠。

It is difficult to apply traditional UHV protection methods to UHV half wavelength AC transmission system.A half wavelength transmission line protection method based on improved transient energy direction was proposed.The measured impedance of half-wavelength transmission lines no longer presents a single linear change with the fault location,so the traditional distance protection cannot be directly applied to half-wavelength transmission lines.However,traveling wave attenuation loss on ultra-long lines is very large,which makes it difficult to accurately detect traveling wave head.Therefore,traveling wave protection is also difficult to be applied to half-wavelength transmission line protection.Therefore,a directional protection method based on improved transient energy was proposed.Transient electrical energy detected at both ends of the line was used to calculate the three-phase instantaneous power of the transmission line,and the transient energy was obtained through the integration of the instantaneous power.A large number of simulations have verified that this method can reliably realize fault identification within and outside the fault zone no matter where the fault point is located on the line.In addition,the polarity of transient energy is not subject to the change of fault Angle and transition resistance,and the required sampling rate is only 10 kHz.The simulation results prove that this method is accurate and reliable.