VIII International Symposium on
Lightning Protection
21st-25th November 2005 – São Paulo, Brazil
MODEL AND SIMULATION IN ATP OF ELECTRIC FENCE WITH
LIGHTNING PROTECTION DEVICE
Marcelo Giovanni B. De Martino
Fernando S. dos Reis
Guilherme A. Dias
Pontifícia Universidade Católica do Rio Grande do Sul – PUCRS
mgiovanni@walmur.com.br
f.dosreis@ieee.org
gaddias@ee.pucrs.br
Av. Ipiranga, 6681 - Porto Alegre - RS – Brasil - CEP: 90619-900 - Fone: (55-51) 3320.3500
Abstract - This paper will present a study of a lighting
protection device used in electric fence installations to
protect the energizer equipment. A model of a rural electric
fence circuit with the energizer connected to the fence with
lightning protection device is presented and simulated in the
Alternative Transient Program (ATP) [1]. With this model is
possible to simulate the circuit with an impulse discharge
provided from the energizer as well an impulse provided
from a lightning stroke. This simulation allows to evaluating
the efficacy of a lightning stroke protection device that is
available on the market and recommended by many
energizer manufacturers. An introduction of the energizer
electric circuit and of the electric fence circuit is presented as
well the simulation of the electric fence model with and
without the protect device. A new lightning protection device
arrangement is presented
grounding theory [4] for the fence circuit is showed in
Figure 2.
1 INTRODUCTION
Figure 2: Equivalent electric fence circuit
The electric fence energizer discharge an electrical
impulse that normally presents amplitude higher than 1 kV
and less than 10 kV on the wire of the fence. This peak
value of voltage will depend of the impedance of the fence
and of the impulse generation circuit design (Figure 1).
The impulse repetition rate shall not exceed 1 Hz and the
impulse duration shall not exceed 10 ms [2].
2 ELECTRIC FENCE PARAMETERS
The fence parameters capacitance and indutance per meter
according to transmission line theory [3] are expressed
trought the equations below:
 
2  h   1

L  
 ln
r0   4. .r0
 2 
C
Figure 1: Impulse Generator Circuit of an Electric Fence
Energizer.
An equivalent electric fence circuit with lumped
parameters, according to transmission line theory [3] and
2  
2h
ln
r0
 wire . wire
. f




(1).
(2).
Where, h is the distance between the conductor and the
soil, r0 is the radius of the conductor, μ is the
environmental permeability,  is the permittivity of the
environmental, ρwire is the wire resistivity, μwire is the wire
permeability and f is the most representative frequency of
the impulse.
VIII International Symposium on
Lightning Protection
21st-25th November 2005 – São Paulo, Brazil
The grounding resistance of many electrodes is expressed
trought the equation below [4]:
Rrods 
F . solo  1 1   8  l  
   ln 

  l x   d  
with the lightning device is showed above is showed in
Figure 4. Figure 5 presents the modeled circuit in ATP.
(3).
Where, x is the distance of the grounding rod up to the
end of the fence, l is the length of the rod, d is the
diameter of the rod, ρsolo is the soil resistivity and F is the
multiplication factor (for 3 rods F is equal to 0.43).
2 LIGHTNING PROTECTION DEVICE
Figure 4: Complete electric circuit with the fence modeled by
lumped parameters.
The energizer circuit needs to be protected from an
electrical impulse provided from a lightning stroke and
transmitted along of the fence. The IEC 60335-2-76:2002
[2] standard demands that the energizers needs to be
resistant to atmospheric surges entering from the fence. It
needs to resist to a 1,2 μs x 50 μs impulse voltage with a
peak voltage of at least of 25 kV applied to the fence
output terminals. Figure 3 presents an illustration of the
instalation of a lighting stroke protection device for
electric fences.
Figure 5: Simulated ATP circuit with the fence modeled with
distributed parameters and frequency dependent.
3.1 Lightning protect device parameters
For the arrester was used the R(i) Type 99 block. The
electrical characteristic of the commercial lightning
arrester modeled is presented in Table 1:
Figure 3: Illustration of the lighting protect device.
This device is arranged with a spring and a lightning
arrester device. The inductor is implemented using a
spring connected in series with the output transformer of
the energizer and has the intention of reduction of the
peak current value and the peak voltage value trough the
secondary winding. The lightning arrester conduce the
surge to the ground. This arrester needs to have a
flashover voltage lower than 25 kV. A parcel of the
lightning current will flow to the energizer and after to the
ground.
3 INPUT DATA
An electric circuit of the electric fence modeled with
lumped parameters and the electric circuit of the energizer
Table 1: Electrical characteristic of the lightning arrester.
Flashover
Discharge voltage value (kV) for each current
Peak Voltage
1.5
5.0
10
15
20
40
kV
kA
kA
kA
kA
kA
kA
16.5
7.4
9.5
10.8
11.6
12.3 15.1
The parameters of the commercial spring (inductor)
modeled for this simulation is presented in Table 2. The
parameters were measured in the LABELO – Electric /
Electronic Specialized Laboratories Calibration and Tests
recognized by INMETRO in the RBC - Brazilian
Calibration Network:
Table 2: Parameters of the spring (inductor) measured in
LABELO.
Spring diameter
45 mm
Wire diameter
2 mm
Number of spirals
115
Spring extended length
1m
Distance between each spiral
5 mm
Electrical Resistance
1Ω
VIII International Symposium on
Lightning Protection
21st-25th November 2005 – São Paulo, Brazil
Measured inductance (10 kHz)
57,5 μH
3.2 Lightning stroke parameters
The lightning stroke is simulated using the Heidler block
that is an impulsive source. It is configured as a 2 kA and
4 μs x 20 μs current source. The source is inserted in the
beginning of the fence.
3.3 Energizer parameters
The impulse generator circuit of the energizer has the
components values obtained from a commercial energizer
recommended to supply up to 5 km fence length.
The storage capacitor C1 is a 9 μF polypropylene
capacitor. The resistance used to limit the in rush current
of the C1 charge is the R1 who has the value of 220 Ω.
The RC circuit is charged with 400 Vdc. The switch
represents a TYN812 thyristor. For the ATP simulation of
the electric fence operation was used a time controlled
switch and for simulation of the discharge of a stroke in
the fence was used a voltage controlled switch with the
Vdrm/Vrrm voltage of the TYN812 thyristor (800 V).
The transformer parameters values for the saturable
transformer model were obtained by the open and short
circuit test. The transformer has a relation of 12.7 and has
the function of isolation between the circuits and voltage
amplification.
Results of simulation of the operation of the impulse
generator circuit modelled in base of a commercial
energizer was collected to evaluate the influence of the
lightning protection device with the inductance of the
spring and the influence of the fence circuit load in the
operation of the energizer. The inductance of the spring
simulated don’t cause substantial difference in the voltage
wave form and peak values for a fence having between 50
m and 5 km length. Figure 6 presents the voltage curve of
the electric impulse generated by the energizer in the
output terminals of the transformer and in the end of the 5
km fence.
3.4 Fence parameters
Figure 6: Impulse voltage from the energizer in the beginning of
the fence and the end of the 5 km fence.
For this simulation the Jmarti model was used to model
the fence. The fence length was selected as a single wire
with 5 km and 0.7 m height. In this case the fence is
simulated with distributed parameters theory.
In the graphics above the peak value is lower than 5 kV
and the flashover of the arrester don’t occur.
3.4 Grounding electrode parameters
5 LIGHTNING STROKE SIMULATION RESULTS
The grounding system is composed by a commercial
copper rod with 2 m long generally used in electric fence
installations. The electric fence manual of many
manufacturers indicates the use of the minimum of three
rods and this number is generally used. The resistivity of
the soil used for this simulation is 100 Ωm. With this
grounding electrode with tree rods is necessary at least of
11.36 kA to soil breakdown occurs. So the equation 3
gives the resistance value of this grounding electrode
(Rrods = 23.4 Ω).
4 ENERGIZER OPERATION SIMULATION
RESULTS
Figure 7 presents the current curve of the lightning source.
VIII International Symposium on
Lightning Protection
21st-25th November 2005 – São Paulo, Brazil
Figure 7: Lightning current source.
5.1 Without lightning protection device
The results presented here are for a lightning stroke in the
fence without lightning protection device. The voltage
curve produced by the lightning source in the output of the
energizer (secondary winding of the transformer) is
showed in Figure 8. The peak value reaches to 2.14 MV
in 4 μs.
This values of current and voltage in the secondary of the
transformer produces serious damaging in the energizer so
is possible that transformer damages before high values of
voltage being applied to the circuit connected to the
primary winding of the output transformer of the energizer
5.2 With lightning protection device
The results presented in this chapter are simulated with a
inductor (spring) and the arrester as is showed in Figure 5.
The voltage and current in the secondary winding of the
transformer are presented in Figure 10.
Figure 8: Lightning voltage curve and current curve measured in
the secondary of the transformer (output of the energizer) in a
fence without protection.
The simulated voltage in the primary winding of the
transformer is showed in Figure 9.
Figure 9: Lightning voltage curve in the primary winding of the
transformer in a fence without protection.
Figure 10: Lightning voltage curve and current curve measured
in the secondary of the transformer (output of the energizer) in a
fence with protection.
The peak voltage in the secondary winding of the
transformer reaches 7677 V. The voltage increases untill
the moment that the arrester starts to conduce. An
energizer accodring to the standard [1] endure this
impulse. Almost all the current flows trough the lightning
arrester. So the current trough the secondary winding of
the transformer is almost all produced by a resonance
between the capacitance and inductance of the fence and
the inductance of the transformer. The graphic current
VIII International Symposium on
Lightning Protection
21st-25th November 2005 – São Paulo, Brazil
curve of Figure 10 is obtained with the C1 charged with
400 V. The energizer circuit designed to resist 25 kV
applied to the output stills open and without short circuit
occurrence so the current in secondary has a low value.
The simulated voltage in the primary winding is showed
in Figure 11.
A new lightning protection device arrangement with to
arresters and one spring is presented (Figure 14). In this
device the second arrester is a low impedance path for the
current where the value of di/dt is so representative that
the spring retains voltage and the voltage applied to the
secondary of the transformer is reduced. The ATP circuit
is presented in Figure 15.
Figure 11: Lightning voltage curve in the primary winding of
the transformer in a fence with protection.
The voltage applied in the switch by the lightning
discharge is showed in the figure 12. The voltage don’t
reaches the value of 800 V so is possible to say that the
thyristor remains open and no current flows trough the
impulse generator circuit of the energizer.
Figure 14: Lightning arrester device composed by one spring
and two arresters.
Figure 12: Voltage produced by the lightning in the switch S.
Figure 15: Simulated ATP circuit with two arresters.
5 LIGHTNING PROTECION DEVICE ANALYSIS
The inductor Lspring implemented by a spring has the
intention to retain voltage and reduce the peak voltage
applied to the output transformer of the energizer. In the
simulation with a 2 kA lightning source the inductor Lspring
has no useless as is showed in Figure 13. The voltage in
the secondary of the transformer reaches the same value
that the value reached in the simulation with the presence
of the spring.
Figure 13: Voltage curve in the secondary winding of the
transformer without spring in the fence.
The voltage curves measured in the output energizer
(second arrester) and in the spring and in the first arrester
is showed in the Figure 16.
Figure 16: Voltage curves measured with the new lightning
protection device.
VIII International Symposium on
Lightning Protection
21st-25th November 2005 – São Paulo, Brazil
This arrangement improves a higher reduction of the
voltage in the output energizer if the inductance of the
spring is increased or if more spring combined with an
arrester is added to the circuit.
6 CONCLUSION
The inclusion of the spring in the fence circuit doesn’t
modify the impulse of the energizer applied to the fence.
The new arrangement with two arresters and one spring is
an excellent alternative to improve the efficacy of this
kind of lightning protection device. This study proves that
the commercial spring combined with on arrester presents
the same result that using just the arrester. In this case the
inductance of the spring is series with the inductance of
the transformer. The inductance of the transformer is
about 100 times higher than the inductance of the spring
so the influence of the spring has no importance. This
study brings to electric fence manufacturers and user a
good explanation about the operation and efficacy of this
kind of protection device. Other important conclusion is
that an energizer with storage energy of 0.72 J installed in
the fence with the conditions described in this study has a
good performance.
7 REFERENCES
[1] “Rule Book Alternative Transient Program”, CAUE –
Argentine commission of EMTP – ATP users,
[2] IEC 60335-2-76:2002, “Household and similar electrical
appliances – Safety – Part 2-76: Particular requirements for
electric fence energizers”, Second edition.
[3] William D. Stevenson, Jr., “Elements of Power System
Analysis”, McGraw-Hill Book Company, 1962.
[4] IEEE Std 142:1991, “IEEE recommended practice for
grounding of industrial and commercial power
systems”.