Lightning Protection System in an Artificial Irrigation

of Farmland at San Pedro / Paraguay Under Standards IEC 62305 and NTC 4552 (Colombian Standard)

Humberto Berni and Milthon Martínez

Management and Projects

Segelectrica Paraguay

Paraguay

hberni@segelectricaparaguay.com

Favio Casas Ospina

Manager

Seguridad Electrica Ltda.

Colombia

favigel@seguridadelectricaltda.com

Abstract—This work present the implementation of an

Lightning Protection System (LPS) in the installations of

artificial irrigation system at the Pire Porã farm, located in the

Rio Verde district of the Department of San Pedro, Paraguay, in

2007, within the framework of safety and electromagnetic

compatibility with the criteria established in national and

international standards, especially IEC 62305 and NTC 4552,

which allow making recommendations for safe assembly and

reliable to people and electronic equipment.

Keywords—lightning protection; grounding system; bonding;

surge protective device (SPD); electrical installations; external

protection; internal protection; International Electrotechnical

Commission (IEC); Colombian Technical Standard (Spanich:

Norma Técnica Colombiana “NTC”); low voltage (LV); medium

voltage (MV); atmospheric electrical discharges.

I. INTRODUCTION

The study site is the artificial irrigation system of farm Pire

Porã located in the Rio Verde district of the department of San

Pedro – Paraguay. The irrigation system of the stay is a central

pivot (520 meters arm) with sprinklers on a shaft that rotates

360 ° covering the land cultivated (soy or corn) in circular

areas (see Fig. 1), for which has 6 distribution transformers

and 15 pumps submersible.

In the past, several components of electrical installation of

the irrigation system were burning, as was the case of

submersible pumps, level controller modules, timers, phase

failure relay, motor soft starters, electronic boards etc.. In

medium-voltage (MV) network a transformer was exploded

per year; also some pumps and unloaders MV were frequently

burned. The main cause of these damages was the induced

surge caused by lightning strikes. Consequences: production

stopped and heavy losses.

The stay's owner (Mr. Martin Gustafson) did some works

and tried to solve the problem for several months, without

success. One major drawback was with the resistance value of

the ground, which was initially greater than 70 ohms, and after

applying various techniques got off below 40 ohms.

Our involvement begins with an assessment of the

conditions of LV and MV network, which feeds the irrigation

system of stay, likewise, with a diagnosed the existent

grounding system.

Applying the methodology outlined in IEEE 81, the

following activities were performed:

Measurement of soil resistivity (Wenner method),

Layered terrain modeling by using computer software,

Measurement of ohmic resistance value of existent

grounding (method of the potential drop with the rule

of 62%),

Modeling of the existing grounding by using computer

software.

Following the technical recommendations of existing rules

on issues of lightning protection and grounding, mainly IEC

62305 and NTC 4552, were made designs and jobs to reach a

lightning protection system (LPS) and to ensure the solution

sought by the stay's owner.

We designed several alternatives of a grounding system to

be suitable for the site conditions and whose resistance value

is less than 10 ohms. By modeling software was made possible

configurations of the grounding; after respective

considerations the recommended configuration was selected.

Finally, in field, was implemented the recommended LPS

that includes:

Relocation of MV arresters (SPD) in distribution

transformers,

Construction of the grounding according the design

and defined configuration,

Maintenance and upgrading of electrical panels,

Assembly of neutral and ground bars on insulators,

Equipotential bonding,

Installation of Surge Protection Devices (SPD) in LV

applications, entre otros.

2013 International Symposium on Lightning Protection (XII SIPDA), Belo Horizonte, Brazil, October 7-11, 2013.

459

Fig. 1. Artificial irrigation. (Rio Verde /San Pedro / Paraguay).

The value of ground resistance obtained was 10, 35 ohms.

The final results show that the system of artificial irrigation

of crops had stabilized and not resubmitted damage during the occurrence of thunderstorms with lightning.

II. OBJECTIVE

Present the implementation of a Lightning Protection System (LPS) for artificial irrigation at the stay Pire Porã, located in the Rio Verde district of San Pedro Department, Paraguay, carried out in 2007, within the framework of the safety and electromagnetic compatibility, with criteria established in the national and international standards, especially IEC 62305 and NTC 4552; issue allowing recommendations to achieve assemblies safe for people and reliable for electronic equipment.

III. SCOPE OF WORK

A. Study of Resistivity

Measurement of Resistivity by Wenner method.

Layered terrain modeling through a software.

B. Diagnostic of the Existent Grounding

Measuring by method of 62% Rule.

Measuring the resistance value of grounding.

Diagnostic grounding (before improvement).

Modeling the ground through software.

C. Improvements to the Grounding System

Designing of a proper grounding system.

Modeling of the recommended grounding system.

Settings that can be implemented.

D. Field Implementation of the Proposed Solutions

E. Final Results

IV. PRELIMINARY INFORMATION

A. Site Location

The approximate geographical coordinates of site are

23°30'09" South (S) and 56°25'10" West (W). Elevation: 125

meters above sea level.

B. Measuring Instrument

Digital Tellurometer (ground tester) that meets AIEE

81/62 and VDE 0413. This equipment operates at 1470 Hz and

is certified by INMETRO of Brazil.

C. Background

The irrigation system of the stay is a central pivot

(520 meters arm) with sprinklers on a shaft that

rotates 360 ° covering the land cultivated (see Fig. 2)

in circular areas, which has 6 transformers and 15

submersible pumps (see Fig. 3).

In the past, several components of electrical

installation of the irrigation system were burning, as

was the case of submersible pumps, level controller

modules, timers, phase failure relay, motor soft

starters, electronic boards etc.

For MV network of the place the statistical suggests

that exploits a transformer per year, the main cause of

damage was the occurrence of lightning.

Also frequently burned pumps and MV unloaders.

V. STUDY OF THE SOIL RESISTIVITY

The measurements of soil´s apparent resistivity were

performed in a crop field near the housing and sheds, by

applying the Wenner method.

Fig. 2. Artificial irrigation system protected.

460

Fig. 3. MV network and pump house of 75 HP.

Field values obtained are as tabulated in Table I, for

different separation distances between electrodes of current

(CE) and of potential (PE).

TABLE I. MEASURED VALUES IN FIELD

Electrode

separation

a (m)

R1 ()

direction

E-W

R2 ()

direction

N-S

R ()

average

ρ

(.m)

=2πaR

1 46,00 46,25 46,13 289,84

2 29,90 26,50 28,20 354,37

3 19,40 23,50 21,45 404,32

4 18,12 16,39 17,26 433,79

5 18,40 16,68 17,54 551,03

6 15,10 15,46 15,28 576,04

7 9,50 10,96 10,23 449,94

8 8,29 10,51 9,40 475,50

Through data simulation are obtained the calculations the

apparent resistivity of the soil, which can be seen in Fig. 4 that

is automatically generated by the software.

Fig. 4. Values calculated by the software.

With the data obtained we proceed to make the soil

stratification: Stratification is done in two layers, of which the

upper layer has an apparent resistivity 247,90 Ω.m to a depth

of 0,97 m, and from this point downward the soil shows

apparent resistivity 539,96 Ω.m. The curve of the resistivity is

obtained as a function of the electrode gap (see Fig. 5).

Fig. 5. Apparent resistivity curve obtained.

The resistivity in the lower layer is higher than in the top

layer so that, for grounding systems to be built on this type of

soil, it is recommended to consider the following aspects:

Bare copper conductor must be horizontally buried at a

depth such that they are in the lower resistivity layer, since

they were more than one meter deep were also on the higher

resistivity layer. We recommend a depth of 0.7 meters.

Electrode head must be in the lower resistivity layer;

recommended depth 0.7 meters.

VI. MEASUREMENT OF RESISTANCE GROUNDING

Measurements were made of the value of resistance

grounding built for the transformer (power application) and of

the value of resistance grounding built for the submersible

pumps (electrical and electronic applications), according to the

methodology described in the IEEE 81.2-1991 (by applying

the method of the 62% rule to the potential drop curve).

A. Diagnostic of Existent Grounding (Before Improvements)

The measurement of resistance value was performed to

grounding built next to cabin of the electronic panel of a

submersible pump of 75 HP, which is part of the irrigation

system of the crops of stay; site that was shown in the figure 3.

According to the results, the resistance official value of this

grounding is 35.45 ohms (R = 35.45 Ω); this value does not

meet the technical criteria of IEC 62305-3, IEC60364-4, NP

337 -7.6.1, NBR 5419-5.1.3.1.2, NTC 4552-5.3.3.3 nor the

provisions of RETIE (Reglamento Técnico de Instalaciones

Eléctricas / Colombia) in Article 15 paragraph 4.

Calculado

Medido

Rho1 = 247,90 Ohm.m H1 = 0,97 m

Rho2 = 539,96 Ohm.m

Fonte = resistividad.rsi

a (m)

1 10

R (

Ohm

.m)

100

1.000

461

The configuration of the grounding evaluated is a grid

rectangular of 6 meters long and 3 meters wide, with a 3-meter

square grid of side. It has six electrodes of grounding type rod,

one in each corner of the rectangle, and two more in the center

of each side. Fig. 6 shows this configuration.

Fig. 6. Configuration of grounding evaluated.

Each electrode was nailed vertically so that the top of it

(head of rod) was two meters deep. The interconnection of the

electrodes are made with bare copper conductor 50 mm²,

buried one meter deep, and connected by exothermic welding.

The physical inspection of materials, techniques and

connections used in this ground (before improvements),

included the following observations:

The rods are steel with copper electrodeposited

coating 12 μm, that is, low copper layer. This

condition does not meet the recommendations of the

technical standards UL 467, NTC 4552-5.3.3.6 Table

10, IEC 60364-5-54, IEC 61024-1 Table 1 and

RETIE-15.3.1.

The separation of rod-type electrodes is only three

meters, which does not meet the technical

recommendations of NFPA and NTC 780-4.13.2.4

4552-5.3.3.2.

The standards NTC 4552-5.3.3, NEC 250.68, NTC-

2050-250112 and RETIE 15.2 recommend at least

one box for inspection and maintenance of

grounding, a situation that is not met in this case.

Missing bonding bridges between the metal structure

of the board and metal elements and between them

and the grounding. Does not meet the

recommendations of IEC 62305, IEEE 1100, NP 337,

NTC 4552-5.3.3.4, NBR 5419, among other.

The electrical panel had no grounding bar.

The electrical system had no equipotential bars.

The electrical system had no Surge Protection

Devices (SPD).

B. Modeling of Existent Grounding (Before Improvements)

The simulation software allow enter the apparent resistivity

data, an estimated value of the earth fault current (1000 A) of

network operator for that site, and defines the configuration of

grounding including all components of the mesh and its

dimensions, with the characteristics shown above in Figure 6.

From that information, the programs executed some

operations and iterations and get an overview of the conditions

of the grounding and the expected value of the grounding:

“Resistência da Malha =33,615 Ohms”.

VII. LIGHTNING PROTECTION SYSTEM (LPS)

The purpose of lightning protection is to control (not

eliminate) the natural phenomenon, directing safely to earth.

Fig. 7 presents a schematic overview of the components of

Lightning Protection System (LPS), derived from IEC 62305-

2 Protection against Lightning Part 2: Risk management and

NTC 4552-2004.

A. External Protection System (EPS)

The IEC 62305-3 in item 5.1.1 indicates that the external

lightning protection, is designed to intercept direct lightning

strikes on a structure and the impacts beside her and conduct

current safely to ground to their then be dispersed so as not to

cause thermal damage or generating mechanical or electrical

arcing which can cause fire or explosion.

The external protection system is basically composed

capture terminals, down conductors and grounding for

lightning protection, connectors, fittings and others like

equipotential bridges.

Fig. 7. Schematic of the components of LPS.

3 m

3 m

3 m

Simbología:

Electrodo tipo varilla 5/8" x 2400 mm x 12 µm

Conductor de tierra de cobre desnudo de 50 mm²

Uniones con soldadura exotérmica

Uso de suelo artificial Fasfgel:

una dosis de 12 kg alrededor de cada

cabeza de electrodo de puesta a tierra

LIGHTNING PROTECTION

SYSTEM (LPS)

External Protection

System (EPS)

Lightningrods

Downcondutors

Grounding System

InternalProtection

System (IPS)

Equipotential Bonding

Surge Protection Device (SPD)

Risk Prevention

Personal Safety Guide

Storms Detection System

462

B. Internal Protection System (IPS)

Internal protection includes equipotentialization of inactive

metal parts and equipotentialization of active lines; the internal protection is based on the concept of zoning.

Get equipotentialization of active lines with the installation

of surge protection device (SPD), in order to reduce to

acceptable levels driven surges that can occur within a facility.

Surge Protection Equipment (SPD) involves installing at the

point of entry into a computer or device on the active

conductors (power, computer, communications, control, etc.)

and grounding, considering the common and differential

protection modes.

The selection of the SPD is based on the principle that low-

voltage equipment can tolerate without damage impulse

voltages given in Table 1 of IEC 60364-4. To set the device

surge protection device (SPD) that require the engines,

machinery, electronics, sensors or transducers, and general

electrical installation of stay and distribution boards, we need

to know the wiring diagram overall network and individual to

each board and each motor starter system.

The analysis of the electrical installation and connections

between equipment and accessories looked at the levels of

voltage and current signal handled by each power and control

that must be protected to minimize the risk of damage to the

components of artificial irrigation system. With the above, we

determined the type and amount of SPD essential for the

protection of equipment and engines of the irrigation system.

On the MV network, it was suggested to place throughout

the line a cable guard to protect against direct impacts of

lightning strikes. Also it recommended placing MT

dischargers each 500 meters to protect the electrical system

from the effects of indirect discharges.

Finally, it is suggested modify the position of the MV

unloaders in each transformer to reduce the chances of damage

due to overvoltages, i.e. perform proper installation of the MV

SPD as illustrated in Fig. 8 and Fig. 9.

Fig. 8. Installation of grounding system and SPD.

Fig. 9. Correct installation of SPD.

463

VIII. DESIGN OF GROUNDING IMPROVEMENTS

A. Grounding for Lightning Protection

Grounding lightning protection is a fundamental part of the

ESP, which contributes substantially to the safety of people

and equipment, provides low impedance to the wave of ray

and allows dissipation and dispersion on the ground

harmlessly. Its resistance must always be less than 10 ohms,

according to the recommendations of all the above standards.

The grounding can be formed by one or more of the

following electrodes: cable rings, vertical or inclined rods

(javelins), centrifugal (dispersion balances) or electrodes

encased in concrete. The distribution of various drivers is

better to a single equivalent conductor length, according to the

recommendation of IEC 61024-1 / IEC 62305-3 and 2.3.2 /

5.4.1.

B. Modeling of Grounding

For the design of a grounding is taken into account soil

resistivity, soil physical structure, security conditions for

people who can move around the buildings and the need to

ensure a lifetime of 20 years.

In the particular case of artificial irrigation of the stay Pire

Porã, proceeded to keep design software the same

configuration of grounding and from it the necessary

modifications were made that could deliver a resistance value

less than 10 ohms.

As the resistivity in the lower layer is greater than in the

upper layer was adapting the configuration considering the

following aspects:

Existing conductors are passed to a depth such that remain

in the lower resistivity layer. The conductors were placed at

0.7 meters and it is considered the application of artificial soil

(gel type) in a dose amount of 12 kg per 5 meters of cable.

Fig. 10. Enhanced configuration grounding for the irrigation system.

With this new configuration modeled in the software,

which can be verified in Fig. 11 (original program window),

we proceed to perform internal calculations for the summary

of the conditions for the modeling and the expected final value

of designed grounding as outlined above.

Fig. 11. Program display: grounding improved configuration.

The important conclusion of this simulation is that the

expected value of the grounding resistance modeled with the

software (9.21 Ω), with the same basic characteristics of

grounding initially built on the site but where indicated

changes were made, meets the recommendations established

by the technical standards IEC 62305-3, IEC60364-4, NP 337-

7.6.1, NBR 5419-5.1.3.1.2, NTC 4552-5.3.3.3 and provisions

laid down in RETIE Article 15 numeral 4.

To ensure the security of the grounding system should

build a dedicated grounding for each use (power, electronics

and lightning protection) and interconnect with each other, as

recommended by IEC 61024-1 / 2.3.1 and IEC 61000-5-

2/5.3.2 regarding interconnection and grounding´s

equipotentialing.

Fig. 12. Interconnection scheme stipulated by standards.

40 m

3 m

6 m

40 m

Simbología:

Electrodo tipo varilla 5/8" x 2400 mm

Conductor de tierra de cobre desnudo de 50 mm²

Conductor de tierra de cobre desnudo de 70 mm²

Pararrayos o

terminales de

captación

Suelo

Conductores

de protección

Conductores

ais lados

Conexiones

equipotenciales

para edificios altos

Bajantes

Conexiones

Puestas a

tierraGrounding

Equipotential bonding for tall buildings

Soil

Lightning Rods

Protection Conductors

Isolated Conductors

Downconductors

Connections

464

IX. CONCLUSIONS

After the improvements designed for grounding system,

the installation of the LV SPD on the panels of the pumps,

optimizing MV network, the relocation of the MV SPD in

distribution transformers, LV electrical adaptations (networks

and boards) and installation of equipotential connections

required for artificial irrigation system of the stay Pire Porã,

we conclude that it was possible to implement the proposed

solutions, which are based on the recommendations of IEC

62305, NTC 4552 and others.

The results of the project, and the sustainability of the

system after six years, demonstrate that if we meet the

recommendations of technical standards then we obtain the

success that is sought in each project of lightning protection

systems.

REFERENCES

[1] F. Casas, “Tierras, Soporte de la Seguridad Eléctrica,” Quinta Edición,

ICONTEC, Bogotá D.C., 2010.

[2] P. Hasee, “Protección contra Sobretensiones de Instalaciones de Baja Tensión, Madrid, 2003.

[3] H. Torres Sánchez, “Protección contra Rayos,” ICONTEC, Bogotá D.C., 2008.

[4] IEC 61024 (1998), Protection of Structures Against Lightning.

[5] IEC 62305-1 / 2 / 3 / 4 / 5 (2005), Lightning Protection.

[6] NBR 5419 (2001), Norma Técnica Brasileira de Proteção de Estructuras contra Descargas Atmosféricas.

[7] NFPA 780 (2004), Lightning Protection Code.

[8] NP 337 (1990), Norma Técnica Paraguaya de Protección de Edificaciones contra Descargas Eléctricas Atmosféricas.

[9] NTC 4552 (2004), Norma Técnica Colombiana de Protección contra Rayos.

[10] IEC 61000 (2002), “Electromagnetic Compatibility (EMC) and Environment.”

[11] IEEE C62.41 (2002), “Recommended Practice on Surge Voltages in Low-Voltage AC Power Circuits (ANSI).”

[12] NBR 5410 (2005), “Instalaciones Eléctricas de Baja Tensión.”

[13] ANSI/IEEE 1100 (1999), “Recommended Practice for Powering and Grounding Electronic Equipment.”

[14] ANSI/IEEE Std 142 (1991), “Recommended Practice for Grounding of Industrial and Commercial Power Systems.”

[15] ANSI/IEEE Std 837 (2002), “Standard for Qualifying Permanent Connections used in Substation Grounding.”

[16] IEC 60364 (2003), “Electrical Installations of Buildings.”

[17] IEEE STD 81 (1991), “Guide for Measurement of Impedance and Safety Characteristics of Large, Extended or Interconnected Grounding System.”

[18] Instituto Colombiano de Normas Técnicas y Certificación (ICONTEC), “NTC 2050 – Código Eléctrico Colombiano,” Primera actualización, Bogotá D.C., 2002.

[19] Ministerio de Minas y Energía de la República de Colombia, “RETIE – Reglamento Técnico de Instalaciones Eléctricas,” Resolución No. 18 0398, Bogotá, 2004.

[20] Administración Nacional de Electricidad (ANDE), “Reglamento para Instalaciones Eléctricas de Baja Tensión”, Paraguay.

[21] Administración Nacional de Electricidad (ANDE), “Reglamento para Instalaciones Eléctricas de Media Tensión”, Paraguay.

465