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Logical Analogy and Electrical Argumentation about Steel Tower as

Down Conductor is in Accordance with

Standard Installation Lightning Protection System

An article for consideration

By:

Januargo

National CME and Design

HCPT Project


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Author : Januargo S. Baskoro 2

Date : Feb 04, 2008

Contents

I. Introduction ................................................................................................................. 3

II. Logically Analogy ....................................................................................................... 5

III. Standard References .................................................................................................. 10

IV. Electrically Argumentation Regarding Tower as down conductor ........................ 11

V. Currently Cases and The Analysis ............................................................................ 14

VI. Conclusion and Solusion Proposal ........................................................................... 16


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I. Introduction

As everybody understood that high building such as telecommunication tower is

something that inviting lightning. Inviting means that when there is no high building at

some area then lightning doesnt come to there unless high level ionization in air at thearea carry the ion to jump from cloud to earth. But if the ionization isnt happened then

lightning jumping only between cloud to another cloud.

Lightning is a jumping ion which normally spread at the surface of cloud to the

counterpart ions which have inverse polarity toward neutralization condition. At some

cloud are not always have same polarity of ion, for example one group of cloud consist of

negative ion (-) then another group of cloud could consist of positive ion (+). Whenever the

two of group become closer until a distance which the energy of charged are strong enough

to jump, so lightning between clouds are exist. But if, in the way of running cloud doesnt

meet the counterpart ion, then the ions are going down because of earth gravitation effect

and forming a path from cloud to earth thus lightning may be happened from cloud to earth

because earth is an extraordinary ions source. The occurrence of lightning from cloud toearth is more possible if there is a better way to reach, those are a high building and tower.

Figure 1. Lightning between clouds


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Figure 2. Lightning between cloud to earth

Figure 3. Lightning from cloud to earth via tower


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II. Logically Analogy

In accordance with previous explanation that lightning is electrical ions that jump each

other with counterpart ions to find neutral condition. The moving ions become an electric

current when it is passed by a conductor. Basic understanding of electrical behavior is

always corresponding to liquid behavior because liquid is visible to be analyzed of its

movement. Electricity is flowing from higher potential to lower potential. Similar with thisthat liquid is flowing from higher pressure of place to lower pressure of place. Moving

electricity need a conductor, liquid need a pipe to move nicely as expected. Size of

conductor is defining of ability to conduct the electric current, size of pipe is also defining

of pipe ability to be passed by liquid.

Logical analogy of lightning protection system at telecommunication tower that on

struck by lightning can be corresponded with water tank system with its pipe channels and

dissipation pipes as shown in Figure 4. The picture is showing how liquid from top tank

flow to bottom via pipe channel, P1 and P2, and the liquid is dissipated completely if the

dissipation pipes are enough.

Figure 4. Logical analogy lightning protection system as tank system with the liquid.

But, when number of dissipation pipes is reduced then liquid will flow to out side via

any pipe that connected to the system as shown in Figure 5. If any part of the out side pipe

consist small cross section and thin, then at that part will receive big pressure thus the

leakage possibility on it can be exist. The illustration is shown in Figure 6.


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Figure 5. Liquid flowing to outside via a pipe that connected to the system.

Figure 6. A small pipe exist at outside pipe.

In Figure 4, 5 and 6 shown system that using 2 kind of channel pipe, P1 and P2.

Assuming that using 1 channel pipe, P2, is enough actually then usage of channel pipe, P1,

giving an extra channel excessively, meaning, the availability of P2 may be removed

because P1 is so bigger than P2. Figure 7, 8, and 9 are showing the system with single

channel pipe.


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Figure 7. Tank system in figure 4 with single down pipe.




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Figure 12

Figure 13

Figure 14


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Capability of conductor to conduct ions is different depending on the material composed

and it is called conductivity. Conductivity is formulated as:

nq=

where,

n is number of electric charge carries,

q is the charge of the ion,

is the mobility of the charged species.

Conductivity is not familiar at peoples ear and it is not understood generally. People can

understand about resistivity that simply inverse of conductivity,

1=

And resistance is an extrinsic property of a device which is represented by the equation

A

lR =

where,

R is resistance of material ( ),

is resistivity of material ( .m),

l is length of material (m) and

A is its cross sectional area (m2)

once more simply equation that taken from basic electronic knowledgement about paralel

combination of resistance is,

RxRRR

1...

2

1

1

11+++=

According to Table 1, shown that each material such as Copper, Aluminium, and Steel has

different resistivity, those are

- Copper = 1.7241x10-6 .cm or equal with 1.7241x10-8 .m- Aluminium = 2.284x10-6 .cm or equal with 2.284x10-8 .m- Steel = 10.4x10-6 .cm or equal with 10.4x10-8 .mSo, for copper cable with cross-sectional area 50 mm2 and its length is as height as tower,

lets say 80 m, the resistance value can be calculated as

6

8

1050

80107241.1

=R

=R 2.75856x10-2

=R 0.027586


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Then for resistance value of Aluminium cable with cross-sectional area 70 mm2 is,

6

8

1070

8010284.2

=R

=R 2.6103x10-2

=R 0.026103

Thus for galvanized steel that has dimension 50mm x 3mm is,

4

8

10150

80104.10

=R

=R 5.5467x10-4

=R 0.055467

Base on standard value of resistance for down conductor that states not bigger than 0.2 so

the value as result of calculation above are so much less, in that means the three of thosecomponent are acceptable to be used.

Table 1. Resistivity of material


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If the resistance calculation is simply implemented to tower shown as follow. For example

72 m 4 legged Angular Tower, many angular tower have same type of top 10 m section,

and the top section has smallest size of legs than bottom section. From tower data, each top

leg is using angle bar 80 x 80 mm with thickness of 8 mm, see Figure 16.

Figure 16. Angle bar 80mm x 80mm x 8mm

The section area is,

1216)872()880( =+= xxA mm2

= 12,16x10-4

m2

Assume that as height as tower are using leg with same type angle bar, so the resistance of

single leg is,

4

8

1016.12

72104.10

=R

=R 0.006158

And value of all leg as paralel combination is

0.006158

1

0.006158

1

0.006158

1

0.006158

11+++=

R

0.006158

41=

R

006158.04 =R

=R 0.001539

This is a very small value (remember the calculation was assuming that tower use same

smallest size of leg as long as height of tower, so the actual could be smaller than the

calculation) and it is acceptable to be used as down conductor.

V. Currently Cases and The AnalysisSo many reports about damage accident that caused by lightning hit the tower such as

1. KWH meter in tower location is burn.2. Neighbors electric equipments are burn, like TV, Radio, Water pump, Lamp etc.

Many opinions arise that says:


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1. It is happened because of tower doesnt equip with down conductor2. It is happened because there is no control pit and the grounding bar is not copper3. It is happened because the grounding resistance is not below than 1 4. It is happened because of electromagnetic effect when lightning is striking

Opinion 1,

It is denied with the explanation in section III and section IV.

Opinion 2,

It is said without analysis and logically thinking.

Opinion 3,

The value of 1 is not mentioned in installation standard of lightning protection

system or in any standard. IEC 62305-3 standard is defining grounding resistance

value as 10 and PUIL (Indonesia Standard) is defining grounding resistance

value as 5

. Technical explanation of this value is too long to be mentioned in thisdiscussion.

Opinion 4,

From the fact in the field, known that portion of damage devices is at power part,

for example, TV burn, radio burn, water pump burn, lamp burn, etc. Which is

electromagnetic field does not cause that defection. Electromagnetic effect as

impact from lightning may cause, human brain disruption, defection on electronic

device such as computer, digital radio etc, but not in power part. So clearly clarified

that all of the defections in these cases are not impacted by electromagnetic field

effect.

So, the analysis of the accident is,

When the lightning striking tower, lightning current is carried down to earth via down

conductor, any down conductor type as mentioned or the tower itself can do the job. In

earth, the lightning current is dissipated through the electrodes. The capability of electrode

to be thru by lightning current depend on surface wide of the electrode that contacted with

earth and impedance of earth self. If number of electrodes are much enough, so the

lightning current can be dissipated immediately, otherwise the currents are looking for any

conductor connected that can be passed, and the alternative selected path is PLN line

toward outside tower area to the neighbor. If the currents that flowing to outside are big,

the defection as mentioned can be happened particularly if current pass a small conductoror big inductance.

Because KWH meter has a coil conductor as inductor inside, so it create high impedance

when a momentary current flow and burn it. Inductor and impedance are not explained in

this writing.


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Every PLN users are suppose to install lightning protection system in their area, but

unfortunatelly it is not done in Indonesia, so when something happen as impact of the

lightning in their neighbor, it may impact to them too.

V. Conclusion and Solusion ProposalSeveral conclusion are taken after all clarification above,

1. Tower as down conductor is in accordance with installation standard of lightningprotection system.

2. All currently defection cases are not caused by the installation lightning protectionsystem without separate down conductor. Those are caused by poor installation of

lightning protection system underground.

3. The value of grounding resistance can not be taken as the only reference. The numberof grounding electrode is one of other consideration.

4. Poor installation of lightning protection system in PLN user, so when lightninghappened in some place, the damage devices can be happened in other placesurrounding.

The author would like to propose two solusions for rectification,

1. Install more standard rods in the tower area as other path for lightning current to bedissipated by earth. The number of additional rods are using trial an error method

because nobody knows the big of lightning current is striking. And also, the author

never did specially the lightning research and never got detail training about lightning,

but this discourse is based on references, basic electrical and logically thinking.

2. Install more standard rods at nearest PLN pole which the line is connected to the site.And pull grounding from each line at the pole via arrestor device. This is intended tointercept lightning current that flowing to out side before touching eighbor devices.

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