基于SSTDR的光伏直流母线损伤检测及定位

Detection and Location of Damage Problems of Photovoltaic DC Bus Based on SSTDR

大型光伏系统的直流母线电缆电压高、线路较长,一般敷设于地下,若其外绝缘层及保护层发生损伤,很可能会引起短路、接地、电弧等故障,危害光伏系统的安全运行。但常规电气测量方法难以发现由外保护层破损所引起的电缆损伤问题,而光伏母线电缆作为双导线型均匀传输线,损伤会引起其特性阻抗发生变化,因此提出了一种基于扩展频谱时域反射法(spread spectrum time domain reflectometry,SSTDR)的母线损伤在线检测方法。在分析光伏直流母线绝缘层及外保护层不同程度破损所引起的特性阻抗变化特性、探讨SSTDR对电缆损伤问题检测可行性的基础上,进而提出了基于SSTDR的、可减少外部环境干扰影响的确定电缆损伤位置的定位策略。在Matlab/Simulink仿真平台及实验室测试平台上分别对基于SSTDR的电缆损伤检测及定位进行了多方面测试,仿真和试验结果证实了该方法对光伏直流母线电缆损伤在线检测及定位的有效性。

The DC-bus cable of a large scale photovoltaic(PV)system with high voltage and long length is usually buried in soil,and its low-frequency electrical parameters hardly change when the cable’s outer protective layers are damaged,which has potential safety hazards leading to faults such as short-circuit,grounding and arc etc.Cables with damaged outer protective layers are difficult to be found using normal electrical detective methods.However,the high-frequency characteristic impedance will change with damage in cables.Consequently,a method based on spread spectrum time domain reflectometry(SSTDR)was proposed to detect damage problems of PV DC-bus cable.The variations of the high-frequency characteristic impedance of damaged PV DC cable were analyzed,thus the feasibilities of detecting the SSTDR-based damaged cable problems were evaluated.And a new location strategy based on SSTDR is also put forward to reduce the influence of external environment interference.The results of simulation and experiments both have proved the validity and efficiency of the SSTDR-based damage on-line detection and location of PV DC bus.