1. CALCULATION OF THE FLASHOVER
RATE DUE TO LIGHTNING WITH THE
EMTP TOOLBOX LIPS
Arnaud GUERRIER 30 / 04 / 09

2. Context
■ For the French overhead lines
 Faults due to lightning = 65% of all types of flashover
■ Flashover rate due to lightning depends on :
 Grounding resistance of towers
 Presence of shield wire
 Tower geometry
 Length of span
 Relief of the area
■ Last important flashover : 3 november 2008 on Néoules –
Réaltor 400 kV double circuit line
 3-phase tripping occuring simultaneously on both circuits
=> load shedding of 1450 MW
2

3. Description of LIPS
■ EMTP Toolbox
■ Development by EDF, HydroQuébec, RTE
■ Calculation of the flashover rate due to lightning function
of the grounding resistance tower
■ Possible studies :
 Evaluation of the flashover rate of an existing line
 Optimization of the number of line surge arresters to install on a
line
 Impact of grounding improvement or installation of sky wires on
the flashover rate
3

4. Description of LIPS
■ Modelling of the overhead line
 Position of conductors and possible shield wires (same tower
used for each span)
 Length of span
 Phase equiped with Line Surge Arrester
■ Calculation of the flashover rate due to lightning with
 ground flash density : number of lightning stroke per year per km²
■ 2 types of flashover :
 Shield failure flashover
 Back flashover
4

5. Description of LIPS
■ Shield failure flashover : ■ Back flashover :
lightning strike on lightning strike on
conductors towers or shield wires
i(t); di(t)/dt
 Overvoltage higher than  A part of the lightning
the lightning withstand current goes into the
voltage of the insulator du grounding electrode
strings  => Overvoltage of the
 Arcing between the spark tower
gap  Arcing if the
overvoltage higher
than the lightning
withstand of the line
5

6. Example of study (1/3)
■ Objective :
 Limit the rate of three-phase tripping
occurring on both circuits of a 400 kV
double-circuit line
 Optimize the number of line surge arresters
to install
■ Current rate calculated with LIPS
■ Modelling of the line
 2 shield wires
 6 spans of 500 m
6

7. Example of study (2/3) : modelling
BFOR
Start a Flashover Rates study
SFFOR
adapt50km.lin
Analyse Flashover Rates study results View results
Lightning1
LINE DATA
model in: adapt50km_rv.pun Lightning current source
found in the LIPS library
6kA, 70us There must be only one per design
sw1 sw2
sw2 6 spans, line length is 3 km sw1
1 1
FD +2 FD +2
a 3 c2phC c2phC 3
b 4 c2phB c2phB 4
c 5 c2phA c2phA 5
c 6 c1phC c1phC 6
a 7 c1phB bfor1 c1phB 7
b 8 c1phA c1phA 8
AC1
+
400kVRMSLL /_300
7

8. Example of study (3/3) : results
■ Number of 3-phase double circuit flashover function of
grounding resistance
■ Installation of line surge arresters necessary for
grounding resistance of tower higher than 30 ohms.
8

9. Impact of Line Surge Arresters on double
circuit line
Flashover rate of the line function of
grounding resistance tower
1 circuit without
LSA
Flashover rate on circuit 2
with LSA on phase 1A and
1C
Flashover rate on circuit 1 with
LSA on phase 1A and 1C
9

10. Conclusion
■ Calculation of the flashover rate due to lightning with
LIPS
■ Measurement : grounding resistance tower
■ For a flashover rate given => optimization of the number
of towers to treat and reducing the costs
10

11. Thank you for your attention
11