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Alexandre Piantini University of São Paulo Lightning Transients in Medium- Voltage Power Distribution Lines V Russian Conference on.

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Presentation on theme: "Alexandre Piantini University of São Paulo Lightning Transients in Medium- Voltage Power Distribution Lines V Russian Conference on."— Presentation transcript:

1 Alexandre Piantini University of São Paulo piantini@iee.usp.br Lightning Transients in Medium- Voltage Power Distribution Lines V Russian Conference on Lightning Protection 17 th – 19 th May, 2016 Saint Petersburg

2 OUTLINE INTRODUCTION LIGHTNING OVERVOLTAGES IN MV NETWORKS Direct strokes Indirect strokes INFLUENCE OF VARIOUS PARAMETERS ON THE LIVs LIGHTNING PROTECTION OF MV NETWORKS Shield wire Surge arresters CONCLUSIONS

3 Lightning: - equipment damages and failures - damages to customer electronic devices - voltage sags - supply interruptions Widespread use + growing dependence on the continuous operation of sensitive electronic equipment  increasing awareness of the importance of mitigating such effects  to evaluate the lightning overvoltages and the effectivenesses of the protective measures INTRODUCTION

4 5.1 km U = f (I, t f, R g, x g, x, V x t,...) MV range! DIRECT STROKES

5 INDIRECT STROKES Courtesy: Prof. S. Yokoyama Magnitudes << than those of the surges related to direct strokes, but the phenomenon is much more frequent  greater no. flashovers (≤ 15 kV).

6 - Magnitude, front time, and propagation velocity of the stroke current - Distance between the line and the lightning strike point - Upward leader / elevated object - Line configuration (horizontal or vertical, rural or urban) - Conductors’ heights, presence of a shield wire or neutral conductor - Observation point - Position of the stroke channel relative to the line - Soil resistivity and ground resistance - Grounding / surge arresters’ spacing - Surge arrester V/I characteristic MAIN PARAMETERS Shorter durations in comparison with the overvoltages caused by direct strokes.

7 SCALE MODEL Measurement: USP (Scale Model) I = 34 kAI = 50 kA Top view - 1:50 scale model (USP) t f = 2  s Calculation: LIOV-EMTP (Nucci et al.) All parameters referred to the FS system VALIDATION OF COUPLING MODELS (ERM) Agrawal et al. (1980) and its equivalent formulations - Rachidi (1993), Taylor et al. (1965) Extended Rusck Model – ERM (1997) Model of the stroke channel The induction mechanism and the problems related to LIV on distrib. lines have been studied for a long time and various models and codes have been proposed for LIV calculations.

8 1:50 SCALE MODEL (USP)

9

10 1) Measured 2) Chowdhuri 3) Liew-Mar "Stroke Current" INDUCED VOLTAGES (Scale Model) d = 1.4 m 14 m (ERM) Line: single-phase, matched “channel”

11 INDUCED VOLTAGES (Scale Model) "Stroke Current" d = 1.4 m 14 m (ERM) Voltage (V)

12 1) t c = 250  s 2) t c = 50  s 3) t c = 25  s (1) (2) (3) t f = 3  s t c = 50  s Stroke current waveshape (t f, t c ) d = 50 m 1.8 km 50 kA 25 kA 0 t f t c  = 500  m  = 0  m

13 Distance line - stroke location (d) d 1.8 km I = 50 kA t f = 3  s 1 2 t c = 50  s 3 1) d = 20 m 2) d = 50 m 1) d = 20 m 2) d = 50 m 3) d = 200 m  = 0  m 1 2 3  = 500  m

14 1)  = 1000  m1)  = 1000  m 2)  = 500  m 1)  = 1000  m 2)  = 500  m 3)  = 0  m Soil resistivity (  ) 50 m 1.8 km I = 50 kA tftf 1 2 t c = 50  s 3 t f = 3  s 1 2 3 t f = 1  s x = 0

15 I = 50 kA t f = 3  s t c = 50  s x = 1000 m x = 150 m  = 500  m Soil resistivity (  ) x = 0 m x = 500 m x = 0 m x = 0 x = 250 m x = 500 m x = 1000 m x = 500 mx = 1000 m  = 0  m

16 Top view (urban line), d = 20 m, h b = 5 m Top view (urban line), d = 20 m, h b = 15 m SCALE MODEL Measurement: USP (Scale Model) I = 50 kA t f = 2  s All parameters referred to the FS system Nearby Buildings

17 PROTECTIVE MEASURES Increasing CFO Shield wire Surge arresters Direct strokes Indirect strokes X MV lines: measures against short interruptions and voltage sags stemmed from lightning:

18 I = 36 kA; t f = 3.1  s; b = 0.11; hc = 600 m; h = 10 m; hg = 9 m; Rg = 0  m x 450 m 70 m Shield wire (ERM) 1:50 scale model, USP SHIELD WIRE - INDIRECT STROKES

19 Shield wire height x I = 24.9 kA; t f = 3.5  s;  = 0 .m h g = 7 m h g = 11 m 10 m R g = 50  450 m 70 m 1:50 scale model, USP

20 Shield wire – relative position h g = 9 m 10 m x 750 m R g = 0  70 m I = 24.9 kA; t f = 3.5  s;  = 0 .m 1:50 scale model, USP

21 I = 50 kA; t f = 3  s; b = 0.3;  = 1000 .m h g = 11 m 10 m RgRg 300 m 50 m SHIELD WIRE – ground resistance ERM x

22 I = 50 kA; t f = 3  s; b = 0.3;  = 1000 .m h g = 11 m 10 m RgRg 300 m 50 m SHIELD WIRE – ground resistance x

23 1:50 scale model Current through the surge arrester (calculated) 1.4 m (70 m) I = 1.32 A x Measured and calculated voltages 1.4 m (70 m) X 0 5 10 t (  s) I (A) 324 216 108 0 10 m Surge arrester Rg = 0  Reference line mr cr mt ct Rg = 0  Test line (23.8 kA) 0 5 10 t (  s) U (kV) 108 72 36 0 SURGE ARRESTERS - INDIRECT STROKES

24 1:50 scale model Decomposition (ct = U s.a. + U d.c. ) U s.a. U lead R = 0  1.4 m (70 m) I = 2.97 A (53.5 kA) x 0 5 10 t (  s) U (kV) 216 144 72 0 Measured and calculated voltages 10 m U s.a. U lead URUR U (kV) 36 18 0 5 10 t (  s) ct SURGE ARRESTERS - INDIRECT STROKES mt ct I = 1.32 A (23.8 kA) mr cr

25 I = 54 kA; t f = 3.2  s; b = 0.11; hc = 600 m; h = 10 m; Rg = 200  m All parameters referred to the FS system x 450 m 70 m LINE WITH SURGE ARRESTERS Surge arresters 450 m (ERM) 1:50 scale model, USP Extended Rusck Model – ERM

26 1:50 scale model I = 38 kA; t f = 3.2  s; b = 0.11; hc = 600 m; h = 10 m; gapless S.A. Surge arresters – ground resistance 162 kV 95 kV 600 m x x I = 38 kA t f = 3.2  s 70 m 31 kV 1:50 scale model, USP

27 x SURGE ARRESTERS - spacing I = 38 kA; t f = 3.2  s; b = 0.11; hc = 600 m; h = 10 m; gapless S.A.;  = 0  m; Rg = 50  x I = 38 kA 70 m 300 m 162 kV 67 kV 125 kV 600 m

28 148 m 174 m 75 m 75 m I = 34 kA t f = 2  s s e = 148 m; s d = 174 m s e = s d = 75 m 1:50 scale model SURGE ARRESTERS - spacing

29 50 m x I = 40 kA; t f = 2  s; t t = 80  s; b = 0.5 h g = 11 m 10 m 50  CURRENT TO GROUND 1000 m IgIg Current (kA)

30 Overvoltages produced by both direct and indirect strokes  voltage sags, supply interrups. and degradation of the power quality indices; U depend on several parameters related to the return stroke current, soil, and network configuration; Line height, stroke current magnitude and front time, distance line-l.s.p., soil resistivity: significantly affect U; Finite length of the stroke channel, stroke current wavetail: minor influence on U. CONCLUSIONS

31 DIRECT STROKES: Protecting is difficult because of the high surge currents, steep rates of rise, and large energy content in lightning flashes. To virtually eliminate flashovers: Arresters (on every pole and every phase) + Shield Wire CONCLUSIONS { Arresters  protect the insulation from backflashover Shield Wire  divert most of the current to the ground (arresters are not subject to much energy input)

32 INDIRECT STROKES: A shield wire may reduce the overvoltages regardless of its position with respect to the phase conductors. Effectiveness decreases with the increase of x g and R g. Line arresters can be effective in reducing the no. of flashovers provided that the arrester spacing is not too large. CONCLUSIONS

33 Благодарим за внимание! THANK YOU FOR YOUR ATTENTION! V Russian Conference on Lightning Protection 17 th – 19 th May, 2016 Saint Petersburg


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