International Telecommunication Union ITU-T Workshop Lightning Protection Technical Session December 2005, Geneva, Switzerland Risk assessment for services Ahmed Zeddam France Telecom R & D Division

ITU-T ITU-T SG 5 Technical Session Lightning Protection 12 December 2005, ITU Headquarters Geneva, Switzerland 2 dates Outline 1. Services considered by IEC Risk assessment for services 3. Comparison with ITU Rec. K46 and K47 4. Example 5. Open issues and future work

ITU-T ITU-T SG 5 Technical Session Lightning Protection 12 December 2005, ITU Headquarters Geneva, Switzerland 3 dates Services in IEC o The standard IEC62305 considers the following services: 1. Telecommunication lines 2. Power lines 3. Pipelines IEC deals with the risk assessment for structures and services IEC deals with the protection of services Telecommunication lines under study Protection of power lines and pipelines under study

ITU-T ITU-T SG 5 Technical Session Lightning Protection 12 December 2005, ITU Headquarters Geneva, Switzerland 4 dates Service to be considered : physical connection The service to be considered is the physical connection between: the switch telecommunication building and the users building or two switch telecommunication buildings or two users buildings, for the telecommunication (TLC) lines; the switch telecommunication building or the users building and a distribution node, or between two distribution nodes for the telecommunication (TLC) lines; the high voltage (HV) substation and the users building, for the power lines; the main distribution station and the users building, for pipes. line equipment termination equipment The service to be considered includes the line equipment and the line termination equipment, such as: multiplexer, power amplifier, optical network units, meters, line termination equipment, etc.; circuit breakers, overcurrent systems, meters, etc.; control systems, safety systems, meters, etc. does not include Protection does not include the users equipment or any structure connected at the ends of the service.

ITU-T ITU-T SG 5 Technical Session Lightning Protection 12 December 2005, ITU Headquarters Geneva, Switzerland 5 dates IEC Risk assessment IEC following sources : IEC provides a method of calculating the risk of loss for a structure/service due to lightning strikes for the following sources : S1 S1: flashes to a structure S2 S2: flashes near a structure S3 S3: flashes to a service S4 S4: flashes near a service Equipment

ITU-T ITU-T SG 5 Technical Session Lightning Protection 12 December 2005, ITU Headquarters Geneva, Switzerland 6 dates IEC : Risk assessment for a service where : number of dangerous eventsNx is the number of dangerous events probability of damagePx is the probability of damage to a service consequent lossLx is the consequent loss Type of loss which may be associated with a service are only: service to the publicL 2: loss of service to the public R2 Risk component R2 economic value R4L 4: loss of economic value (service and loss of activity) Risk component R4 NOTE : Loss of human life NOTE : Loss of human life associated with a service is not considered is not considered in IEC standard Rx=Nx·Px·Lx Risk components for a service

ITU-T ITU-T SG 5 Technical Session Lightning Protection 12 December 2005, ITU Headquarters Geneva, Switzerland 7 dates IEC : Risk assessment for a service Source of damage Flash striking the service S3 Flash striking near the service S4 Flash striking the structure S1 Risk component R` V Physical damage R` W Failure of connected equipment R` Z Failure of Connected equipment R` B Physical damage R` C Failure of connected equipment Risk for each type of loss R` 2 (public service) R` 4 (econom. value) **** **** **** **** **** Risk components for a service

ITU-T ITU-T SG 5 Technical Session Lightning Protection 12 December 2005, ITU Headquarters Geneva, Switzerland 8 dates IEC : Risk assessment for a service Partitioning of a service into sections S S : To assess each risk component, the service could be divided into sections S S. However a service may be, or may be assumed to be, a single section. For all risk components (R' B, R' C, R' V, R' W, R' Z ), sections S S are mainly defined by: type of service (aerial or buried) factors affecting the collection area (Cd, Ce, Ct ) characteristics of service ( type of cable insulation, shield resistance). Further sections may be defined according to: type of connected apparatus; protection measures existing or to be provided. Partitioning of a service into sections should take into account the feasibility of implementation of the most suitable protection measures.

ITU-T ITU-T SG 5 Technical Session Lightning Protection 12 December 2005, ITU Headquarters Geneva, Switzerland 9 dates IEC : Risk assessment for a service Decision to protect a service : identification of the service to be protected and its characteristics identification of all the types of loss in the service and the relevant corresponding risk R (R' 2 & R' 4 ) evaluation of risk R for each type of loss (R' 2 & R' 4 ) by comparison R 2 or R' 4 evaluation of need of protection, by comparison of risk R 2 or R' 4 for a service with the tolerable risk R T evaluation of cost effectiveness of protection by comparison of the costs of total loss with and without protection measures. In this case, the assessment of components of R 4 for a service is to be performed in order to evaluate such costs

ITU-T ITU-T SG 5 Technical Session Lightning Protection 12 December 2005, ITU Headquarters Geneva, Switzerland 10 dates IEC : Risk assessment for a service Procedure to evaluate the need of protection: Procedure to evaluate the need of protection : identification of the tolerable risk R T comparison of the risk R with the tolerable value R T R R T is not necessary If R R T lightning protection is not necessary R > R T protection measures shall be adopted If R > R T protection measures shall be adopted in order to reduce R R T for all risks to which the service is subjected. Typical values of tolerable risk R T Types of lossR T (y -1 ) Loss of human life or permanent injuries10 –5 Loss of service to the public10 –3 Loss of cultural heritage10 –3

ITU-T ITU-T SG 5 Technical Session Lightning Protection 12 December 2005, ITU Headquarters Geneva, Switzerland 11 dates IEC : Risk assessment for a service Risk components for a service Source of damage Type of damage S3 Lightning flash to a service S4 Lightning flash near a service S1 Lightning flash to a structure Resulting risk according to the type of damage D2 Physical damage R' V =N L ·P' Vi ·L' V R' B =N D ·P' Bi ·L' B R F R F =R` V +R` B D3 Failure of electrical and electronic systems R' W =N L ·P' Wi ·L' W R' Z = (N I – N L ) P' Z L' Z R' C =N D ·P' Ci ·L' C R O R O =R` Z +R` W +R` C Resulting risk according to the source of damage R D R D =R` V +R` W R R I =R` Z +R` B +R` C

ITU-T ITU-T SG 5 Technical Session Lightning Protection 12 December 2005, ITU Headquarters Geneva, Switzerland 12 dates Comparison with K46 and K47 most important component : For telecommunication lines the risk component R' Z is generally the most important component : Rec. 46 Rec. 46 provides risk assessment for only the component R' Z and gives the associated protective measures S4 : Lightning flash near a service Rec. 47 Rec. 47 considers the other risk components (R' B, R' C, R' V, R' W ) and gives the associated protective measures S3 : Lightning flash to a service S1 : Lightning flash to a structure IEC Additional information on risk component Rz evaluation are given in IEC Equipment along the line Ks Shielding factor Ks

ITU-T ITU-T SG 5 Technical Session Lightning Protection 12 December 2005, ITU Headquarters Geneva, Switzerland 13 dates Comparison with K46 and K47 Ks The factor Ks play an important role in the determination of the probability PLI Some values of this probability depending on the resistance R S of the cable screen and the impulse withstand voltage Uw of the equipment are given in Table B.7 of Annex B of IEC Probability P' Z of internal systems failure due to flashes near the service depends on the service shield (RS), the impulse withstand voltage, the typical protection measures and the SPDs at the entrance of the structure Shielding factor

ITU-T ITU-T SG 5 Technical Session Lightning Protection 12 December 2005, ITU Headquarters Geneva, Switzerland 14 dates Comparison with K46 and K47 NO SPDs: P' Z = P LI SPDs: P' Z lower between P SPD and P LI U w (kV) No shield K se : Shielding factor related to the earth K SS : Shielding factor related to the shield 5<R S 20 (Ω/km) 1< R S 5 (Ω/km) R S 1 (Ω/km) 1 1,5 2, ,4 0,2 0,1 1 0,5 0,2 0,1 0,05 0,3 0,15 0,06 0,03 0,02 0,08 0,04 0,02 0,008 0,004 0,04 0,02 0,008 0,004 0,002 Red values missed in the IEC standard K se : shield not bonded to the same B.B. to which equipment is connected K ss : shield bonded to the same B.B. to which equipment is connected Probability P' Z of internal systems failure due to flashes near the service P LI

ITU-T ITU-T SG 5 Technical Session Lightning Protection 12 December 2005, ITU Headquarters Geneva, Switzerland 15 dates Comparison with K46 and K47 RsKs Relation between Rs and Ks is given in Table B.5 of Annex B of IEC Shielding factor K.46 gives shielding factors for external lines, while Table B.5/IEC addresses internal wiring. K.46 gives shielding factors for external lines, while Table B.5/IEC addresses internal wiring. Shielding factors for internal wiring have been treated in K.surge Type of internal wiringK S3 Unshielded cable – no routing precaution in order to avoid loops 1) 1 Unshielded cable – routing precaution in order to avoid large loops 2) 0,2 Unshielded cable – routing precaution in order to avoid loops 3) 0,02 Shielded cable with shield resistance 4) 5<R S 20 Ω / km 0,001 Shielded cable with shield resistance 4) 1 < R S 5 Ω / km 0,0002 Shielded cable with shield resistance 4) R S 1 Ω / km 0,0001 1) Loop conductors with different routing in large buildings (loop area in the order of 50 m 2 ). 2) Loop conductors routing in the same conduit or loop conductors with different routing in small buildings (loop area in the order of 10 m 2 ). 3) Loop conductors routing in the same cable (loop area in the order of 0,5 m 2 ). 4)Cable with shield of resistance R S (Ω / km) bonded to equipotential bonding bar at both ends and equipment connected to the same bonding bar. NOTE NOTE More precise evaluation of K s for shielded and unshielded sections can be found in the ITU Recommendation K.46.

ITU-T ITU-T SG 5 Technical Session Lightning Protection 12 December 2005, ITU Headquarters Geneva, Switzerland 16 dates Comparison with K46 and K47 Shielding factor related to earth Shielding factor related to earth K se K46 gives a more precise evaluation of the shielding factor related to earth Annex A of IEC gives some guidance : " This situation is called Shield not bonded to equipotential bonding bar to which equipment is connected in Table B.7 of the IEC standard " Need to use two standards for the risk assessment ! Shielding factors for internal wiring are treated in K.surge Shielding factor

ITU-T ITU-T SG 5 Technical Session Lightning Protection 12 December 2005, ITU Headquarters Geneva, Switzerland 17 dates Example section 1 b structure b (switching) HbHb a HaHa 3Ha3Ha section 2 structure a (user) 3Hb3Hb StructureDimensions (m) (L · W · H) Location factor C d n Number n of services to structure a25 · 20 ·1523 b20 · 30 · 100,510 TbTb T 1/2 TaTa Mean values of relative amount of loss per year relevant to risk R2 were assumed Lf = 3·10 -3 (loss due to physical damage) Lo =10 -3 (loss due to failure of internal systems)

ITU-T ITU-T SG 5 Technical Session Lightning Protection 12 December 2005, ITU Headquarters Geneva, Switzerland 18 dates Example ParameterCommentSymbolValue Soil resistivity ( m) 500 Length (m) - LcLc 600 Height (m) Buried -- Line location factor Surrounded CdCd 0,5 Line environment factor Rural CeCe 1 Line shielding resistance ( km) - R0,5 Type of line shield Lead-- Shield characteristics No contact with soil KdKd 0,4 Type of line insulation PaperU w (kV)1,5 Type of equipment in transition point T b Electronic U w (kV) 1,5 (1) Type of equipment in transition point T 1/2 None -- Protection measures None KpKp 1 (1) Enhanced level of ITU-T Recommendation K.20 CommentSymbolValue ( m) LcLc 800 Aerial HcHc 6 Surrounded CdCd 0,5 Rural CeCe 1 Unshielded-- PlasticU w (kV)5 Electronic U w (kV) 1,5 (1) None -- KpKp 1 Section S1 Section S2

ITU-T ITU-T SG 5 Technical Session Lightning Protection 12 December 2005, ITU Headquarters Geneva, Switzerland 19 dates ExampleParameterS1S2Line R' B(a) (1) - 0,261 R' B(b) (1) R' C(a) (2) -0,0873 R' C(b) (2) R'VR'V 0,02820,15660,1848 R'WR'W 0,00080,05220,053 R=R' B(a) +R' B(b) +R' C(a) +R' C(b) +R' V +R' W 0,5861 R' Z(Ta) (5) 0,29671,54781,845 R' Z(Tb) (6) 0,01191,54781,59 R' Z(T1/2) (7) 0,29671,54781,845 R' 2(Ta) =R+R' Z(Ta)2,4311 R' 2(Tb) =R+R' Z(Tb)2,1761 R' 2(T1/2) =R+R' Z(T1/2)2,4311 Risk R'2 for unprotected line (values x ) The value of the risk R'2 is greater than the tolerable value R T = 10 –3, therefore the line needs to be protected

ITU-T ITU-T SG 5 Technical Session Lightning Protection 12 December 2005, ITU Headquarters Geneva, Switzerland 20 dates Example R' Z R' 2 R T Ta, Tb and T1/2 Due to the risk component R' Z in section S2, the risk R' 2 overcame R T in transition points Ta, Tb and T1/2 R' 2 P SPD = 0,03 In order to reduce the risk R' 2 below the tolerable value, it is enough to select SPDs in accordance with LPL III, i.e. P SPD = 0,03 TaT1/2 The SPD installation at transition points Ta and T1/2: reduces the probabilities P' Z (Ta) and P' Z (T1/2) to the value P SPD ; reduces the probabilities P' Z (Ta) and P' Z (T1/2) to the value P SPD ; does not affect the probabilities P' V and P' W ; does not affect the probabilities P' V and P' W ; does not affect the probabilities P' B and P' C relevant to section S2 because it is aerial ; does not affect the probabilities P' B and P' C relevant to section S2 because it is aerial ; does not affect the probabilities P' B and P' C relevant to section S1 because they are lower than P SPD does not affect the probabilities P' B and P' C relevant to section S1 because they are lower than P SPD see Annex D of IEC Risk R'2 for unprotected line R' 2(Ta) =R+R' Z(Ta) 2,4311 2,4311 x R' 2(Tb) =R+R' Z(Tb) 2,1761 2,1761 x R' 2(T1/2) =R+R' Z(T1/2) 2,4311 2,4311 x 10 -3

ITU-T ITU-T SG 5 Technical Session Lightning Protection 12 December 2005, ITU Headquarters Geneva, Switzerland 21 dates ExampleParameterS1S2Line R' B(a) (1) - 0,261 R' B(b) (1) R' C(a) (2) -0,0873 R' C(b) (2) R'VR'V 0,02820,15660,1848 R'WR'W 0,00080,05220,053 R=R' B(a) +R' B(b) +R' C(a) +R' C(b) +R' V +R' W 0,5861 R' Z(Ta) (5) 0,29671,54781,845 R' Z(Tb) (6) 0,01191,54781,59 R' Z(T1/2) (7) 0,29671,54781,845 R' 2(Ta) =R+R' Z(Ta)2,4311 R' 2(Tb) =R+R' Z(Tb)2,1761 R' 2(T1/2) =R+R' Z(T1/2)2,4311 Risk R'2 for unprotected line Risk R'2 with SPDs at T 1/2 and Ta (P SPD = 0.03)Parameter S1S1S1S1 S2S2S2S2Line R' B(a) -0,261 R' B(b) R' C(a) -0,0873 R' C(b) R'VR'V 0,02820,15660,1848 R'WR'W 0,00080,05220,053 R = R' B(a) + R' B(b) + R' C(a) + R' C(b) + R' V + R' W 0,5861 R' Z(Ta) 0,01780,05530,0731 R' Z(Tb) 0,0119-0,0119 R' Z(T1/2) 0,01780,05530,0731 R' 2(Ta) = R+ R' Z(Tb)0,6592 R' 2(Tb) = R+ R' Z(Ta)0,598 R' 2(T1/2)= R+R' Z(T1/2)0,6592 (values x )

ITU-T ITU-T SG 5 Technical Session Lightning Protection 12 December 2005, ITU Headquarters Geneva, Switzerland 22 dates Open issues and future work Amendment of K46, K47, K39 Amendment of K46, K47, K39 Align with IEC risk approach ? Align with IEC risk approach ? Probability of a customer injury or death when using telecommunications equipment Probability of a customer injury or death when using telecommunications equipment see Phil's presentation Amendment of IEC Amendment of IEC Shielding factor (Kss, Kse) & Rules for the use of Table 7 (probability for shielded sections) Shielding factor (Kss, Kse) & Rules for the use of Table 7 (probability for shielded sections) see Celio's presentation Probability of a customer injury or death when using telecommunications equipment Probability of a customer injury or death when using telecommunications equipment Take into account the information of K. surge Take into account the information of K. surge Protection of powerlines and pipelines Protection of powerlines and pipelines Global approach of risk for Structure and Service ? Global approach of risk for Structure and Service ? Evolution of the network architecture Evolution of the network architecture Risk assessment and protection of Customers near an RBS Risk assessment and protection of Customers near an RBS Risk assessment and protection of FTTC, FTTB, FFTH.. Risk assessment and protection of FTTC, FTTB, FFTH..