Sadovic Lightning 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

BACK FLASHOVERS

SHIELDING FAILURES

INDUCED

I0, tf

I0, tfI0, tf

THE ANNUAL NUMBER OF LIGHTNING

OUTAGES PER 100 KM OF LINE LENGTH

LINE LIGHTNING PERFORMANCE

LINE BACK FLASHOVER RATE

THE ANNUAL OUTAGE RATE CAUSED BY A

FLASHOVER OF LINE INSULATION

RESULTING FROM THE STROKES TO THE

TOWERS AND TO THE GROUND WIRES

I0, tf

Back

flashover

LINE SHIELDING FAILURES

I0, tf

Shielding failure

Shielding failure

flashover

THE ANNUAL NUMBER OF LIGHTNING EVENTS

THAT BYPASS THE OVERHEAD GROUND WIRES

AND TERMINATE ON THE PHASE CONDUCTORS

THE ANNUAL NUMBER OF

FLASHOVERS CAUSED BY

SHIELDING FAILURES

Additional Shield Wires

Underbuilt Ground Wire

Line Surge Arrester

Increasing Insulation

Guy Wires

Foot_resistance

improvement

HOW TO IMPROVE LINE LIGHTNING PERFORMANCE?

1 LSA

per tower

2 LSA

per tower

LINE SURGE ARRESTER APPLICATION

123 kV Line Dubrovnik - Ston

U(t)

tt1

(U - t) Insulation characteristic(s1)

U0

(s2)

t2

U1

U2

ELECTROMAGNETIC TRANSIENTS SIMULATION

MODEL OF THE LINE INSULATION FLASHOVER

vl - Leader speed (m/s)

d - Arcing distance (m)

ll - Leader length (m)

u(t) - Applied voltage (kV)

E0 = 520 (kV/m)

Flashover models:

Constant voltage

Equal area

Leader propagation

Leader propagation model:

d lu(t)

)(

170

)( 0015,0

0d

tu

l

l eEld

tudv

1

))(( 0

0

k

DUtU k

t

t

gap

d Ugap(t)

dD

ddU

dUU

ddUU

dt

U

s

s

2045,0

822)2

710400(

4959,0

550)8

710400(

[IEEE] (kV) )710

400(

75,02

%500

75,0%508

75,0

U(t)

t ( s)2

U50%

8

U0

U2 s

D

EQUAL AREA FLASHOVER MODEL

dD

k

dU

2045,0

1

4950

EMTP_RV Model data:

[d - arcing distance in meters]

g

lci

I

I

RR

1

22 lc

g

gR

EI

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)]

I

I (kA)

Ig

Linear Resistance

Non-Linear Resistance

U (kA)

ELECTROMAGNETIC TRANSIENTS SIMULATION

SOIL IONIZATION TOWER FOOTING RESISTANCE MODEL

hav

W

IC

Back

Flashover

QUICK BACK FLASHOVER RATE COMPUTATIONS

W - Line shadow width

A - Line attraction area

hav - Tower average height

IC - Back flashover critical current

W

100 km

A = 100 x W (km2)

Stroke current is changed until

flashover [IC obtained]

ANN

WA

bRW

hR

GL

a

ava

100

2

14 6,0

QUICK BACK FLASHOVER RATE COMPUTATIONS

W

100 km

A = 100 x W (km2)

)31

(1

1

6,2CI I

PC

ANN

WA

bRW

hR

GL

a

ava

100

2

14 6,0

CIL PNBFR 6,0

W - Line shadow width

b - Ground wire separation distance

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

hav

W

IC

Back

Flashover

)24

(1

1

4SPS

IEEE DISTRIBUTION

i0 (t)

t ( s)

tf

I0

I0/2

tt

S (kA/ s)

IS PP

)31

(1

1

6,2IPI

0

ft

IS

CURRENT PEAK

STEEPNESS

Equivalent Front Time

Equal Probability

No DC Resistance

[Ohm/km]

Outside diameter

[cm]

x [m] y [m] y [m]

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

1

2

3

4

123 kV TRANSMISSION LINE DUBROVNIK STON

Un= 123 kV

Length = 46 km

Span = 200 m

L = ZT/v

v - velocity of light hT = 28,9 m

lprop = 20 m

ZT = 184

Propagation

element

L1 = 2,8 H

L3 = 1,37 H

L2 = 1,37 H

LINE SURGE ARRESTER

Current (A) Voltage (V)

1000 239000

2500 252000

5000 275000

10000 291000

20000 324000

40000 357000

Rated voltage: 123 kV

IEC Class II

Polymer housed

00km/year)(strokes/1 105215

(km2) 21210,0100100

(m) 210010522

(m) 1059,281414 6,06,0

ANN

WA

bRW

hR

GL

a

ava

123 kV TRANSMISSION LINE DUBROVNIK STON

Ground flash density: 5 strokes/km2/year

Length = 46 km

Using EMTP_RV find IC (Critical current)

)31

(1

1

6,2CI I

PC

CIPBFR 1056,0

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

Flashover Tower 2

Phase conductor C

Stroke Sub circuit

AUTOMATIC BACKFLASHOVER SIMULATIONS

EMTP_RV is running in the loop until gap signal > 0

Critical current

Back flashover rate

FUTURE WORK > 3D EGM

WS - SIMULATED WIDTH

STRIKING DISTANCES

1. TO PHC & GW:

rS = A I B

[A=10, B=0,65]

2. TO TOWERS:

rTT = k rS

[k= 1 – 1,1]

3. TO EARTH:

span

rE

rT2

rT1

x0

y0

WS

DOWNWARD

LEADER

I0, tf

0,65

E vIEEE: r 3,6 1,7 ln(43 y ) I

rGW = rPHC = rNO = rS

GW

PHC

x0

dl

hl

rGW

rPHCrNO

WS/2 WS/2

NEARBY

OBJECT

DOWNWARD

LEADER APPROACHES

UNDER ANGLE

I0, tf

2cos2

f

FUTURE WORK > 3D EGM

FUTURE WORK > sigma slp like interface

EMTP_RV modeling and transients computation

Monte Carlo Statistical Study and 3D EGM