IEC_81-254e-INF.pdf

81/254/INF For IEC use only 2004-09-03 INTERNATIONAL ELECTROTECHNICAL COMMISSION TECHNICAL COMMITTEE No.81:LIGHTNING PROTECTION REPORT OF CONVENOR Of IEC TC 81/WG 10(to be discussed under draft agenda item 9 at forthcoming TC 81 meeting to be held in Seoul 20th and 21st October 2004)1.General The task of WG10 is to prepare IEC 62305-5,which deals with the Lightning protection of services.2.Date and place of meetings Since the last meeting of IEC held in Palma de Mallorca on September 2003 WG10 met on:14/15 October 2003 in Stockholm,Sweden 21/22 April 2004 in Frankfurt,Germany Regarding the membership of WG10 it can be noticed that there is now some experts from Power Companies but nobody for Pipelines.Further meeting is scheduled for:18/19 October 2004 in Seoul(Korea)3.Status of work The last meetings of WG10 were mainly devoted to finalize the parts of IEC 62305-5 dealing with the protection of telecommunications lines and powerlines on the basis of the consideration of the comments related to the IEC 62305-5 circulated as 81/220/NP.By lack of experts and contributions the part related to pipelines is always under study.Regarding the risk assessment for services in IEC 62305-2,WG10 has produced contributions to WG9 through the Convenor and the Secretary.3.1 Remarks on IEC 62305-2 Comments and amendments of IEC 62305-2 were submitted to the convenor of WG9 to have IEC 6235-5 in line with the previous IEC 61663-2 and the Recommendation K46 of ITU-T.The majors points concerns:Addition of note stating that Information on section to be considered and the notion of transition point were introduced in IEC 6230565 Amendment of Table B.7 related to shielding factor and addition of a note stating that more precise evaluation of PLI can be found in IEC 62305-5 and ITU Recommendation K46.Addition of the concept that the risk component Rz should be evaluated for each transition point between two sections.3.2 Work on IEC 62305-5:Lightning protection-Protection of services The last draft of IEC 62305-5 was prepared by adding the information needed on portioning of a service and the protective measures of powerlines based on the collection of practices in different countries.The following points were considered:Addition of section dealing with the need of protection at the transition points.The risk component Rz defined in IEC62305-2 should be evaluated as seen from each of the transition points of the telecommunication line.2 81/254/INF The value of Rz for a given transition point is the sum of the Rz components relevant to each section of the line.The value of the shielding factor of each line section depends on the shielding characteristic of the considered transition point and on the earth connection of the shield.Introduction of the shielding factor The use of properly earthed/bonded shielded cables attenuates the lightning induced surges on the telecommunication line.This attenuation can be expressed as a shielding factor(Ks),which is a number between 0(for perfect shielding)and 1(for no shielding).In order to evaluate the shielding factor,the shield must be continuous through all the extension of the shielded section(s)and connected to the bonding bar at both ends The shielding factor related to the shield(Kss)and the shielding factor related to the earth(Kse)were both defined.Amendment of the section dealing with the use of surge protective devices SPD News section 6 dealing with the protection of powerlines According to the reference configuration,the protective measures will deal only with distribution lines(MV and LV lines).The following protective measures or combination of methods have been considered:installing a buried instead of an aerial section in order to improve the installation factor of the different line sections;shielding to improve the shielding factor of the different line sections by selecting shielded cables instead of unshielded or selecting cables with reduced shielding factors;use of surge protective devices(SPDs);use of a supporting wire,as air-termination of a lightning protection system dedicated to the aerial cable.The draft of IEC62305-5 has been produced as CD and sent to IEC81 for its next meeting.4.Forecast work for the future WG10 agreed to have its next meeting in Seoul(Korea)on October 18-19,2004.The meeting will be devoted to complete the standard and to analyse the comments related to the CD.10 is to prepare IEC 62305-5,which deals with the Lightning protection of services._