Lightning Effect on Copper and Optical Fiber (FTTN) Access Networks of Telecommunication Systems

This paper presents a study of lightning effect on copper and optical fiber (fiber to the node) public switched telephone network (PSTN) in Sri Lanka. The study covers, firstly modeling and simulation of each PSTNs, secondly development and testing of PSTN laboratory prototypes and finally a case study for a selected real network. The individual PSTNs were modeled by PSCAD/EMTDC software and were verified in the laboratory by applying lightning surges to the developed prototypes. The study was extended by considering the effects of typical earth resistances in the PSTN and possible multiple reflections. In the case study, first the RLC parameters of the PSTN were estimated by field and laboratory measurements. Then, the PSTN was modeled and analyzed in PSCAD/EMTDC software. It was found that significant components of lightning surges may transfer to the consumer side unless proper surge protective devices are used. Further, this effect may be higher in the optical fiber network compared to the copper network. A significant effect may also appear at the subscriber side due to multiple reflections and the earth resistances characterized by high soil resistivity.