Abstract
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.
Highlights
Lightning is an electrostatic discharge occurring between electrically charged regions within clouds or between a cloud and the ground
4.2 Effect of multiple reflection Objective of this study is to investigate the effect of the multiple reflections in public switched telephone network (PSTN) and see whether it can create a potentially harmful situation to equipment and to the subscriber
Effect of multiple reflections was analyzed for the worst case which can be happened in the copper wired access network
Summary
Lightning is an electrostatic discharge occurring between electrically charged regions within clouds or between a cloud and the ground. The first type is called “direct lightning surge” i.e. due to high voltage surges generated by direct lightning discharges striking to the telecommunication cables or devices. Lightning usually do not strike on telecommunication cables directly If it does, the result could be melting of the cable and significant damages to the connected devices. A proper protection system should: (a) provide protection against indirect lightning strikes, (b) provide an effective earth termination network for discharge of lightning current and (c) prevent entering of conducting surges to equipment cabins [9,10,11]. This study basically addresses three important aspects of lightning on telecommunication systems: the instantaneous voltages created by the travelling wave due to indirect coupling mechanism, the grounding effect of the metallic cable sheath upon the resulting induced surge and the reflection and oscillation phenomena of transient voltage caused by the connecting cables. A case study conducted with the aid of a practically verified simulation model in order to depict so called aspects is presented
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