LIGHTNING PROTECTION SYSTEM STUDY USING EARTH ELECTRODES AND

ENHANCEMENT MATERIALS

ByBuba, Sani Dahiru

GS25573Master of Science

Supervisors: Dr. Wan Fatinhamamah Wan Ahmad, Chair

Dr. Jasronita Jasni, Member Prof. Madya Dr. W. N. Wan Daud,

Member

Presentation outline

Introduction Problem statement Objectives Methodology

Literature review

Installation of earthing systems/earth resistance measurements

Results and Findings

Introduction

What is Earthing ?

‘The provision of permanent and continuous conductive

path to the ground having sufficient capacity to carry any

fault current liable to be imposed upon it, with sufficiently

low impedance to limit voltage rise above ground

potential, and be able to facilitate the operation of

protective devices’ Hinde (2009).

Introduction contd.

Commonly used earthing structures includes single

horizontal wire, vertical rods, ring conductors,

multiple conductors forming triangular or

rectangular shapes and earthing grids, Liu (2004).

Introduction continued

What is the purpose of earthing systems?

at power/low frequency is basically to provide a safe path/return for dissipation of stray/faults currents.

for transient/lightning protection is to dissipate transient charges, static charges, electromagnetic interference (EMI), and radio frequency interference (RFI).

for signal/high frequency systems, is to provide zero signal reference.

Introduction contd.

Other purposes for which earthing is provided include;

to ensure safety of general public and personnel

against contact with energized circuits or systems.

protection of equipments against damage by

overvoltages

to provide safe and correct operation of power system both under normal, earth fault and transient conditions.

Introduction contd.

Types of earthing

functional earthing system, specific to sensitive

electronic equipment and data networks, safety is

not a major concern

system earthing, neutral point of a transformer

Introduction contd.

equipment earthing, connection of metallic

parts to earth

protective earthing refers to bonding of all

exposed metallic and extraneous conductive

parts

Problem statement

The earth resistance of an electrode system consists of,

Resistance of the earth electrode

Contact resistance between the electrode and soil

Resistance of the soil surrounding the earth electrode

The first two resistances are negligible for most practical

purposes, IEEE Std 142-2007.

Problem statement contd.

Resistance of the soil is therefore dependent on the soil resistivity.

Soil resistivity ρ varies with depth from the surface, type of soil,

concentration and type of soluble salts (chemicals) in the soil, moisture

content and soil temperature. In other words, the resistivity is that of

the electrolyte in the soil’, IEEE Std 142-2007.

Objectives

Determine soil properties relevant to earthing systems

Install earthing systems using chemical

enhancement materials (CEM) and natural

enhancement materials (NEM).

Determine the best performed enhancement

material and earthing installation.

Methodology

Selection of experiment sites Soil tests

Physical analysis Chemical analysis

Installation of soil parameter data loggers

Installation of earthing system using CEM and NEM

Earth resistance measurements

Selection of experiment site

Site 1 Near Canteen Site 2 near guard house

Results of soil tests

Results for Site 1 Results for Site 2

Selection of site contd.

• BS7430-1998, recommends that where there is an option, the following types of soil should be chosen ,

wet marshy ground Clay, loamy soil etc.

Literature Review

Chemical enhancement materials (CEM)

Soil resistivity may be reduced anywhere from

15% to 90% by chemical treatment of the soil,

(IEEE Std 142-2007).

Uman (2008), suggested that the resistivity of

soil can be reduced by adding chemicals to the

soil surrounding a grounding electrode.

Literature review contd.

Brieals (1991), recommended the use of

common salting materials such as sodium

chloride (NaCl), magnesium chloride (MgCl2),

calcium chloride (CaCl2 ) and copper sulphate

(CuSO4 ) for soil enhancement purposes.

Wan Ahmad (2010), used NaCl, NH4Cl, CuSO4,

Na2S2O3, and MgCl2 around a circular trench.

Literature review contd.

Natural enhancement materials (NEM)/backfill

BS7430-1998, Recommends replacement of soil

immediately around an electrode with a lower

resistivity material to improve earth electrode

contact resistance may be used in special or

difficult locations.

Literature review contd.

Gomes et al. (2010), industrial wastes, bentonite and NaCl

Kumarasinghe (2008), paddy dust, coir peat, bentonite

Eduful et al. (2009), palm kernel fibre

Reference diagram for CEM installation, (Megger manual)

CEM

Cross section of circular trench and dimensions

Installation of earthing systems contd.

CEM

Measure intervals and mark electrode positions

Drive earth electrode into the soil

Dig circular trench

Pour/place CEM inside circular trench

Backfill the trench with soil

Grass clearing for installation of earthing system

Earth electrode being driven into the soil

circular trench marked out

Completed circular trench

Installation of earthing system contd.

‘Fourty to ninety pounds of chemical will initially be

required to maintain effectiveness of earthing system for

two to three years’, MIL STD HBK-419A, Vol. 1(1987).

1 pound = 0.453kg

40 pounds = 18.12kg assumed to be effective for 2 years

Experiment was designed for one year, the quantity of

CEM used was 18.12/2 = 9.06 kg rounded to 10kg.

Typical CEM placed in circular trench

CEM

A typical circular trench backfilled with soil

Earth electrode

Typical PVC earth chamber placed on earthing installation

Installation of earthing system using NEM

NEM

Bore/drill hole

Fill the hole with NEM and compress

Drive earth electrode at the middle

Cover the top with soil

Cross section of earthing installation using NEM as infill, Chen (2009).

Drilling hole for installation of earthing system using NEM

Hole drilling equipment

Water pump

Earth resistance measurements

Earth resistance measurement was conducted using 3-point fall of potential method (Wenner method).

Earth Tester Megger DET3TC

Potential and current probe positions were fixed using rule of 62%

Measurements were conducted for different angles between current and voltage probes initially.

Earth resistance measurements contd.

Zero degrees between potential and current

probes was chosen for simplicity and popularity.

Additional data recorded during measurements

includes, ambient temperature, ambient

weather, soil condition and humidity.

Table 1 Results and Findings for CEM installations

Results for CEM contd.

Link to tables of percentage reduction of earth resistance for CEM

Table 2 Results and Findings for NEM installations

Results for NEM contd.

Link to tables of percentage reduction of earth resistance for NEM

Table 3 comparison between CEM and NEM

Table 4 soil condition before and after experiment

Comparison contd.

Environmental condition after 365 days

Contributions of the study

The results from this study has revealed that, soil

treatment with suitable CEMs can significantly

reduce earth resistance.

Performance of CEM for reduction of earth

resistance was reported in terms of actual earth

resistance and percentage values.

Contributions contd.

10kg of CEM is effective for one year in clay

loam type of soil.

Soil treatment with CEMs raises the pH from

acidic to alkaline which is good for plant growth.

Soil treatment with CEMs slightly changes the

soil texture from clay loam to sandy clay loam.

Contributions contd.

Electrode encasement/enhancement using

biodegradable materials are effective for short

periods only.

Suitable maintenance period was recommended.

Performance of CEMs in clay loam type of soil

was reported.

Conclusion

It is concluded from the study that;

In terms of earth resistance readings,

comparison between different earthing

installations in the CEM category indicated that

CaCl2 is the best performed CEM.

In terms of percentage reduction of earth

resistance, NaCl is the best performed CEM.

Conclusion contd.

In NEMs category, comparison between different

earthing installations in terms of earth resistance

readings, and percentage reduction of earth

resistance indicated that bentonite installation is

the best performed.

Conclusion contd.

When the performances of CEM and NEM

installations are compared, it was found that CEM

installations performed better than NEM

installations both in terms of earth resistance

readings and percentage reduction of earth

resistance.

Conclusion contd.

Therefore CEMs such as CaCl2, NaCl, MgCl2, and

Na2S2O3 are considered effective in reduction of

earth resistance in clay loam type of soil.

Similarly, NEMs such as bentonite and palm

kernel fibre are also considered an effective

backfill materials for reduction of earth

resistance.

Table 5 List of Publications

THANK YOU

Graphs

Soil parameter graphs

Different angles of measurement

References

[1] Hinde, S., Overhead Line Guidelines, British Columbia Safety Authority Information Bulletin No: B- E30903121, 12th March, 2009.

[2] Liu, Y., Transient Response of Grounding Systems Caused by Lightning: Modelling and Experiments, PhD Dissertation from the Faculty of Science and Technology, University Uppsala, Sweden, November, 2004.

[3] IEEE STD 142TM: 2007, Recommended Practice for

Grounding of Industrial and Commercial Power Systems, Pp169.

References contd.

[4] British Standard BS7430-1998, Code of Practice for Earthing.

[5] Uman, M. A., the Art and Science of Lightning Protection, Cambridge University Press, New York, 2008, Pp. 85.

[6] Briels, G., Chapter 4 of Electrical Hazards and Accidents, Van Nostrand Reinhold, New York, 1991, Pp. 72-73.

References contd.

[7] Wan Ahmad, W. F., Abdul Rahman M. S., Jasni, J., Ab Kadir, M. Z., A., and Hizam, H., Chemical Enhancement Materials for Grounding Purposes, Presented at the 30thInternational Conference on Lightning Protection, ICLP 2010, Cagliari, Sardinia, Italy, 13-17 Sept.2010.

[8] Gomes, C., Lalitha, C., and Priyadarshanee, C., “Improvement of Earthing Systems with Backfill

Materials,” presented at the 30th International Conference on Lightning Protection, ICLP 2010, Cagliari, Sardinia, Italy, 2010.

References contd.

[9] Kumarasinghe, N., “A Low Cost Lightning Protection System and its Effectiveness,” presented at the 20th International Lightning Detection Conference and 2nd International Lightning Meteorology Conference,

Tucson, Arizona, U. S. A, 2008.

[10] Eduful, G., and Cole, J. E., “Palm Kernel Oil Cake as an Alternative to Earth Resistance Reducing Agent,” presented at the Power Systems Conference and Exposition, Seattle, WA, 2009, p.2

References contd.

[11] A Practical Guide to Earth Resistance Testing, www.megger.com/det

[12] Grounding, Bonding, and Shielding for Electronic Equipment and Facilities, Military Handbook,

MIL- HDBK-419A, Vol. 1, December 1987, Ch2. Pp 63.

[13] Chen, L. H., Chen, J. F., and Wang, W. I., “Research on Used Quantity of Ground Resistance Reduction Agent for Ground Systems,” European Transactions on Electrical Power, Online, Wiley Inter Science, 2009.