An update on power line surge protection techniques for telecom munication facilities

The distributed topology of modern telecommunication networks has turned the reliability of their power supply and energy systems into a major design consideration. Energy systems supporting critical telecommunication facilities are exposed to a multitude of power supply abnormalities which are external to the telecommunication network, one of those being power line surges or transient overvoltages. The network reliability which significantly defines the availability of telecommunication services and the quality of service offered to customers, as well as the operational expenses of telecommunication companies, can be significantly impaired if adequate power surge protection techniques have not been deployed. This paper serves a dual purpose: to provide a tutorial review of the power surge protection technology as well as to report on significant operational results obtained over a period of 3 years in the Telecom Italia network in Italy. The first part of the paper reviews the various techniques used for the power surge protection of telecommunication facilities. A brief comparison between the various alternatives is outlined. A detailed update on the recent developments in the international standards (both in Europe as well as in North America) regulating the safe operation as well as the performance of surge protection devices is also presented. The efforts of the international standardization community towards the convergence of the regional standards into a truly international standard are also briefly described. The second and most important part of the paper describes the efforts of Telecom Italia, during the last three years, to optimize the protection of its network facilities. Statistical data collected during this period are presented and analyzed. Various techniques implemented in the field in different types of installations are also detailed and compared. The paper also reports on the significant operational expenditure associated with damages caused by power surges, as well as their impact on the network availability figures. Finally, significant operational expense reductions achieved through the implementation of certain techniques are presented in detail. In summary the paper provides a state of the art review of the field of surge protection as it relates to telecommunication applications and offers significant practical engineering guidelines developed through field implementations at the Telecom Italia network.