Sadovic Lighting Performance Computation

EMTP-RV USER GROUP MEETING EMTP_RV MODELLING FOR THE TRANSMISSION LINE LIGHNTING PERFORMANCE COMPUTATION T. Sadovic, S. Sadovic Dubrovnik 30.04.2009

LINE LIGHTNING PERFORMANCE THE ANNUAL NUMBER OF LIGHTNING OUTAGES PER 100 KM OF LINE LENGTH I0, tf BACK FLASHOVERS I0, tf I 0, t f INDUCED SHIELDING FAILURES

LINE BACK FLASHOVER RATE THE ANNUAL OUTAGE RATE CAUSED BY A I0, tf FLASHOVER OF LINE INSULATION RESULTING FROM THE STROKES TO THE TOWERS AND TO THE GROUND WIRES Back flashover

LINE SHIELDING FAILURES THE ANNUAL NUMBER OF LIGHTNING EVENTS THE ANNUAL NUMBER OF THAT BYPASS THE OVERHEAD GROUND WIRES FLASHOVERS CAUSED BY AND TERMINATE ON THE PHASE CONDUCTORS SHIELDING FAILURES I0, tf Shielding failure flashover Shielding failure

HOW TO IMPROVE LINE LIGHTNING PERFORMANCE? Additional Shield Wires Underbuilt Ground Wire Increasing Insulation Line Surge Arrester Guy Wires Foot_resistance improvement

LINE SURGE ARRESTER APPLICATION 123 kV Line Dubrovnik - Ston 2 LSA per tower 1 LSA per tower

ELECTROMAGNETIC TRANSIENTS SIMULATION MODEL OF THE LINE INSULATION FLASHOVER (s2) Flashover models: U(t) (s1) (U - t) Insulation characteristic Constant voltage U2 Equal area U1 Leader propagation U0 Leader propagation model: t2 t1 t u (t ) u (t ) 0 , 0015 d vl 170 d E0 e d ll d l vl - Leader speed (m/s) u(t) d - Arcing distance (m) ll - Leader length (m) u(t) - Applied voltage (kV) E0 = 520 (kV/m)

EQUAL AREA FLASHOVER MODEL d Ugap(t) U(t) t 710 ( U gap (t ) U 0 ) k D U (400 ) d (kV) [IEEE] U2 s t0 t 0, 75 k 1 U50% D 710 U0 U8 s U 50% (400 ) d 550 d 80, 75 2 8 t ( s) U0 0,9 U 50% 495 d EMTP_RV Model data: 710 U2 s (400 ) d 822 d [d - arcing distance in meters] 2 0, 75 U0 495 d D 0,2045 d k 1 D 0,2045 d

ELECTROMAGNETIC TRANSIENTS SIMULATION SOIL IONIZATION TOWER FOOTING RESISTANCE MODEL I Rlc Ri U (kA) Linear Resistance I 1 Ig Non-Linear Resistance Eg Ig 2 I (kA) 2 Rlc Ig Rlc – low current tower footing resistance ( ) Ri – tower footing impulse resistance ( ) I – impulse current (kA) Ig – soil ionisation limit current (kA) Eg – soil ionisation critical electric field (kV/m) – [Eg = 400 (kV/m)]

QUICK BACK FLASHOVER RATE COMPUTATIONS Stroke current is changed until flashover [IC obtained] W - Line shadow width A - Line attraction area IC hav - Tower average height IC - Back flashover critical current 100 km A = 100 x W (km2) W Back hav Flashover Ra 14 hav, 6 0 W 2 Ra b A 100 W N L NG A W

QUICK BACK FLASHOVER RATE COMPUTATIONS 100 km IC A = 100 x W (km2) W 1 Ra 14 hav, 6 0 PI C I Back 1 ( C ) 2,6 W 2 Ra b hav Flashover 31 A 100 W BFR 0,6 N L PI C N L NG A W - Line shadow width b - Ground wire separation distance W NL - Number of strokes collected [str/100km/year] NG – Ground flash density [str/km2/year] BFR - Back flashover rate 0,6 > Takes into account strokes hitting shield wire

IEEE DISTRIBUTION 1 i0 (t) S (kA/ s) CURRENT PEAK PI I 1 ( ) 2,6 I0 31 I0/2 1 t ( s) STEEPNESS PS S 4 tf tt 1 ( ) 24 Equal Probability PS PI I0 S tf Equivalent Front Time

123 kV TRANSMISSION LINE DUBROVNIK STON No DC Resistance Outside diameter x [m] y [m] y [m] [Ohm/km] [cm] at midspan 1 0.1444 1.708 2.5 22.7 14.1 2 0.1444 1.708 -3 20.5 11.9 3 0.1444 1.708 3.5 18.3 9.7 4 0.4555 0.9 0 28.9 21.3 4 L1 = 2,8 H L2 = 1,37 H Un= 123 kV Length = 46 km L3 = 1,37 H 1 Span = 200 m L = ZT/v 2 v - velocity of light hT = 28,9 m Propagation 3 element lprop = 20 m ZT = 184

LINE SURGE ARRESTER Rated voltage: 123 kV IEC Class II Polymer housed Current (A) Voltage (V) 1000 239000 2500 252000 5000 275000 10000 291000 20000 324000 40000 357000

123 kV TRANSMISSION LINE DUBROVNIK STON Ground flash density: 5 strokes/km2/year Length = 46 km Ra 14 hav, 6 0 14 28,90, 6 105 (m) W 2 Ra b 2 105 0 210 (m) A 100 W 100 0,210 21 (km2) N L N G A 5 21 105 (strokes/100km/year) Using EMTP_RV find IC (Critical current) 1 PI C I 1 ( C ) 2,6 31 BFR 0,6 105 PI C

AUTOMATIC BACKFLASHOVER COMPUTATIONS EMTP_RV Line section model created Netlist file obtained

AUTOMATIC BACKFLASHOVER SIMULATIONS Tower Model> Sub circuits Air gap model Signal = 0: No flashover Signal =1: Flashover

AUTOMATIC BACKFLASHOVER SIMULATIONS Tool developed to run EMTP_RV in a loop Initial stroke current Current step

AUTOMATIC BACKFLASHOVER SIMULATIONS EMTP_RV is running in the loop until gap signal > 0 Stroke Sub circuit Flashover Tower 2 Phase conductor C

AUTOMATIC BACKFLASHOVER SIMULATIONS EMTP_RV is running in the loop until gap signal > 0 Critical current Back flashover rate

FUTURE WORK > 3D EGM I0, tf WS - SIMULATED WIDTH STRIKING DISTANCES DOWNWARD LEADER 1. TO PHC & GW: rT1 rS = A I B rT2 [A=10, B=0,65] span 2. TO TOWERS: rTT = k rS rE [k= 1 – 1,1] 3. TO EARTH: x0 WS y0 IEEE : rE 3,6 1,7 ln(43 yv ) I0,65

FUTURE WORK > 3D EGM DOWNWARD I0, tf LEADER APPROACHES UNDER ANGLE 2 f cos2 rGW rGW = rPHC = rNO = rS rPHC GW rNO NEARBY PHC OBJECT hl dl x0 WS/2 WS/2

FUTURE WORK > sigma slp like interface EMTP_RV modeling and transients computation Monte Carlo Statistical Study and 3D EGM

Sadovic Lighting Performance Computation

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