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Date:27 March 2009Comments on draft document Reclassification of
a Non-credible Contingency Event as a Credible Contingency Eventdue
to Lightning
Mark MillerGeneral Manager OperationsNEMMCO
Enquiries:Dr Wallace Vosloo+27 (0)21 918 8942
Dear Mr Miller,
Comments on draft document Reclassification of a Non-credible
Contingency Event as a
Credible Contingency Event due to Lightning follows:
1. Proposed changes to Figure 1 in Appendix A.
2. The Cause identified and corrected decision in Figure 1 needs
to be explained in thetext. The utility should prove the validity
of the correction.
3. The Assets characteristics improved to remove risk decision
in Figure 1 needs to beexplained in the text. The utility should
validate that the risk is removed or minimised.
For your information extracts from EPRI AC Transmission Line
Reference Book - 200 kV andAbove, Third Edition is attached in
Appendix B.
Doing a lightning performance study, using a program such as
TFLASH, is a handy tool tohelp the utilities to identify and
calculate risks (see typical example study done for Powerlinkin
Queensland in Appendix C).
Hope the above helps
Always at your service
Dr Wallace L VoslooCorporate Specialist High Voltage
EngineeringPr. Eng, NHD, B.Sc(Phy), Ph.D(Eng.Sci), SMSAIEE,
SMIEEE
Corporate Services DivisionERIDLower Germiston Road Rosherville
PB 40175 Cleveland 2022 SATel +27 11 6295536 Fax +27 11 629 5301
www.eskom.co.za
Directors: RM Godsell (Chairman) PJ Maroga (Chief Executive) LCZ
Cele SD Dube LG Josefsson (Swedish)HB Lee (Korean) WE Lucas-Bull PM
Makwana J Mirenge (Rwandan) JRD Modise AJ Morgan U NeneCompany
Secretary: TN MsomiEskom Holdings Limited Reg No 2002/015527/06
8/3/2019 229-0001
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Appendix A: Proposed changes to Figure 1.
Performance over time
No events
Identifiedin the past five years
One event
Identifiedin the ast five ears
More than one event
Identified and confirmedin the past five years
Classified as
Possible
Classified as
Probable
Classified as
Proven
Y
Y
NAssetscharacteristicsimproved toremove risk
Causeidentified and
corrected N
Vulnerable *
* eligible to bereclassified as acredible contingencyevent
during alightning storm
