光纤复合架空地线直流融冰绝缘化改造对地线绝缘子与并联放电间隙的电气要求

Electrical Requirements for Ground Wire Insulator and Parallel Discharge Clearance During Insulation Reconstruction for OPGW DC De-icing

为满足光纤复合架空地线(OPGW)直流融冰的需要,同时解决环流损耗和易遭雷击断股等问题,须将OPGW接地方式由目前常用的逐塔接地改造为分段或全线绝缘、单点接地方式;OPGW经地线绝缘子及其并联放电间隙与杆塔相连。为此,提出了OPGW直流融冰绝缘化改造对并联放电间隙的电气要求,分别对正常运行时、地线直流融冰条件下和雷击情况下的并联放电间隙电气性能进行了详细的计算分析和试验研究。结果表明:并联放电间隙距离选择应满足感应电压和直流融冰电压的耐受要求,还应保证并联放电间隙在雷电过电压下可靠击穿;要满足工频感应电压的耐受要求,间隙距离可取20~100 mm;要满足直流融冰电压为-20 k V×(1±10%)的耐受要求,间隙距离应大于60 mm;考虑到间隙放电的分散性,间隙距离宜适当增大,推荐值为70~80 mm;70~80 mm间隙距离的雷电冲击放电电压一般不大于100 k V,线路遭受雷击时,地线绝缘子与并联放电间隙所承受的电压至少为885 k V,甚至高达数MV,并联放电间隙能可靠击穿,从而确保地线绝缘子的运行安全性。该研究结果可为OPGW直流融冰绝缘化改造提供理论支撑和数据支持。

In order to satisfy the demands of DC de-icing of optical fiber composite overhead ground wire （OPGW） and solve questions such as circulating current loss and its liability in suffering from lightning stroke and broken, the ground- ing method of OPGW must be changed from the current commonly-used method of being grounded at every towers to being grounded at one tower. OPGW would be connected with tower by ground wire insulator, which should be equipped with protective discharge clearance. Consequently, we put forward an idea that the clearance distance should not only sat- isfy the requirements of withstanding the induced voltage and the de-icing voltage, but also ensure reliable breakdown at lightning voltage. Moreover, we calculated and experimentally researched the electrical characteristics of discharge clearance at normal operation, on de-icing, and in lightning conditions, respectively. Results indicate that discharge clear- ance should be set from 20 to 100 mm to withstand power frequency induction voltage. Furthermore, discharge clearance should be set more than 60 mm to withstand DC de-icing voltage, which is -22 kV at most. Considering the dispersion of clearance discharge, the clearance should be appropriately increased. The recommended value of discharge clearance is from 70 to 80 ram. The lightning impulse discharge voltage of such clearance is generally not more than 100 kV. However, as transmission line is struck by lightning, overvoltage on insulator and clearance is 885 kV at least, even up to a few MV. Clearance can be broken down reliably to ensure safety of insulator. Research results can provide a theoretical support and data support for OPGW de-icing insulation reconstruction.