Electric Power Systems Research 231 (2024) 110330

Contents lists available at ScienceDirect

Electric Power Systems Research
journal homepage: www.elsevier.com/locate/epsr

A field study on the energy dissipation associated with step and touch
voltage in earthing systems encased in earth enhancing compounds
Lasantha Chandimal a, *, Manoj Rajakaruna b, Sankha Nanayakkara c, Sidath Abegunawardana a,
Mahendra Fernando a, Vernon Cooray da

Department of Physics, University of Colombo, Colombo, Sri Lanka
Department of physics and astronomy, University of Toledo, USA
NitroCapt AB, Uppsala, SwedendDepartment of Electrical Engineering, Uppsala University, Swedenbc

A R T I C L E I N F O

A B S T R A C T

Keywords:
Earthing
Earth-Enhancing-Compound
Step-voltage
Touch-voltage

An extensive field experiment was conducted to investigate the effects of earth-enhancing compounds onearthing systems. Four identical vertical earth rods were installed, each encased in concrete, Bentonite, and twocommercial enhancing materials. Lightning impulse signals were injected into all electrode arrangements, andthe measured responses were used to analyse the associated risks of step and touch voltages. The peak voltage
values and the corresponding energy dissipation for each measurement were calculated and compared to those ofa reference electrode. The analysis of step voltage measurements and the corresponding energy dissipation
demonstrated that the use of concrete exhibited greater advantages than the use of Bentonite. However, touch
voltage measurements and the associated energy dissipation indicated that despite the lower touch voltage
exhibited by Bentonite, its energy dissipation exceeded that of the reference electrode. Consequently, the uniquefindings reveal that specific variations of earth-enhancing compounds can exhibit reduced earth impedance andlower step or touch voltages while also yielding higher energy dissipation, introducing an unforeseen risk of
injury. © 2017 Elsevier Inc. All rights reserved.

1. Introduction
Lightning is a fascinating yet dangerous atmospheric occurrence andsignificantly affects all grounding system designs. The purpose of alightning grounding system is to safely channel lightning currents safely
into the earth, minimizing equipment damage and risk of injury. While
direct lightning strikes are commonly perceived as the main cause ofhuman injury, other hazardous mechanisms exist, such as side flashes,
upward leaders, and ground currents [1,2]. This article primarily fo­
cuses on ground currents.
Upon striking, lightning significantly elevates the electric potential
at the entry point, referred to as Ground Potential Rise (GPR). It is fol­
lowed by a potential decrease along its dissipation path, creating a
voltage difference along the current flow. This voltage difference canlead to electric shock risks for individuals in proximity, especially due tostep and touch voltages. Step voltage can route current from one leg andleave from the other, and touch voltage can create a current path fromhand to feet, exposing vital organs. Therefore, GPR, step, and touch

voltages raise significant safety concerns in lightning-related scenarios.
It is imperative to have an efficient low-resistance earthing system tomitigate such ground current injuries. This can be achieved by replacing
the immediate soil surrounding the earthing system with EarthEnhancing-Compound (EEC) [3]. Theoretically, for a 3 m long verticalearth rod, approximately 50% of the earth resistance is concentrated
within just 0.15 m radially from the rod [4]. Bentonite and concrete
show promising performance in challenging soil conditions [5–9]Bentonite can be further enhanced by mixing it with chemicals, and it
slightly outperforms new formulations of natural EEC types in terms of
impulse impedance [10,11].
The overarching goal of these grounding techniques is to minimize
equipment damage and prevent injuries. Guidelines such as IEEE Std
80–2013 [12] provide comprehensive grounding grid design recom­
mendations, including maximum allowable step and touch voltages
during fault conditions. While the risk of injury is often related tomaximum exposed voltage, calculating energy absorption during elec­
tric shocks could be a more suitable predictor of damage [2,13]. A
comprehensive study using live animals found that the minimum lethal* Corresponding author.
E-mail address: aplasantha@yahoo.com (L. Chandimal).
https://doi.org/10.1016/j.epsr.2024.110330
Received 5 September 2023; Received in revised form 22 February 2024; Accepted 13 March 2024
Available online 30 March 2024
0378-7796/© 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

L. Chandimal et al.

Electric Power Systems Research 231 (2024) 110330

Four rods were enclosed in different cylindrical EEC types, each around
100 mm in diameter. One rod served as a reference, directly buried in
the natural soil. These included electrodes encased in concrete,
Bentonite, and two rods encased in distinct commercial EECs referred toas EEC1 and EEC2. A simplified arrangement is illustrated in Fig. 1(a),while Fig. 1(b) depicts the four EEC-covered electrodes.

Nomenclature
V
Vmax
Imax
Z
Zfop
Estep/touch
Rearth
RH
L

ρ1
ρ2

d1
d2

Voltage on the resistive load (V)Maximum value of the voltage signal (V)Maximum value of the Current signal (A)Earth Impedance (Ω)
Earth impedance from FoP curve (Ω)
Electrical energy dissipated from step or touch-voltages(J)
Earth resistance (Ω)
Human body resistance - taken as 1000 (Ω)
Length of the earth electrode (m)Soil resistivity (Ωm)
EEC resistivity (Ω)
Earth electrode diameter (Ω)
EEC diameter (Ω)

4. Measurements
A portable combined wave generator [19] was employed introduce
impulse signals into the grounding system. The generator can deliver
voltage signals of 1.2/50 μs at 2 kV and current signals of 8/20 μs.
Current measurements were taken using a current transformer with a 10
A/V ratio, while a differential probe with a 1000:1 ratio was utilized tomeasure potential differences. The waveforms were captured using a
PicoScope (6000 series) connected to a laptop.
4.1. Summary of instruments and measurements• 2D Soil resistivity profile (Fig. 2) using ZZ resistivity tester - FlashRES-universal, the 64-channel free configuration resistivity/IP
exploration system• Earth resistance variation for each electrode using the Fall of Po­
tential (FoP) method. Measurements were taken at one-meter in­tervals using KYORITSU digital earth tester model 4105A• Current and voltage data to measure the FoP for an injected impulse
signal in order to calculate energy dissipation under touch voltage
conditions• Current and voltage data are used to measure the step voltage for an
injected impulse signal in order to calculate energy dissipation understep voltage conditions.

energy level from a lightning strike is 62.6 joules per kilogram [14].
However, energy-based calculations are less prominent in lightning
earthing literature.
2. Experimental objectives
This article builds upon a sequence of lab and field tests [15,16]
aimed at understanding lightning GPR and subsequent step and touch
voltages when EECs are employed. Examinations of step or touch volt­
ages often employ AC signals [17], which enables the utilization of asingular voltage value for analysis. Nevertheless, when impulse signals
are used, the maximum value or a value at a designated time point isusually used [18]. However, capturing the characteristics of an impulse
signal through a single value does not provide a comprehensive under­
standing of its impact, particularly in relation to potential injury risks.
Hence, the research introduces and compares energy-centric method­
ologies for assessing step and touch voltage characteristics.

4.2. Resistivity measurements
Fig. 2 illustrates the 2D resistivity profile of the soil cross-section, as
measured by the ZZ resistivity tester. The color bar represent the re­sistivity of the soil cross-section in ohm-meters (Ωm). The data wascollected using the Wenner method, with measuring electrodes buried at
one-meter intervals along a 50-meter straight line from the corre­
sponding earth rod arrangement. The figure shows relatively constantresistivity values below three meters, but significant variation in theupper layers.
Table 1 shows the resistivity values used in calculating the earth
resistance for EEC-encased electrodes. EEC1 and EEC2 values were ob­tained from the manufacturer’s websites, and Bentonite and concrete

3. Experimental arrangement
The experiment was conducted in a spacious, open area withoutmajor constructions nearby. Some tall trees and vegetation were pre­sent. Measurements were taken during the wet season, with care to
avoid substantial rain within a week. Five 1.2-meter vertical earth rods
were driven into the ground, spaced about 1 meter apart. All rods were
16 mm in diameter, featuring copper-bonded sheaths and steel cores.

Fig. 1. (a) Vertical Earth Electrode Encased in EEC, (b) Electrodes in EECs a. Concrete, b. Bentonite, c. EEC1, d. EEC2.
2

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Electric Power Systems Research 231 (2024) 110330

Fig. 2. 2D soil resistivity profile of the site.

configuration. A simplified representation of the FoP test and step
voltage test is depicted in Fig. 3.

Table 1
Resistivity values of selected EEC types.
Material

Resistivity (Ωm)

Bentonite
EEC 1
EEC 2
Concrete

1.8
0.02
0.01
10

4.4. Impulse signal
A typical voltage and current impulse signal injected during theexperiment is shown in Fig. 4 in a short time span. As and whenrequired, all impedance calculations were performed considering thepeak voltage and peak current values. Consequently, the impedance (Z)can be modelled as below [23];resistivity were taken from [20,21]. The average resistivity of the sur­rounding area was taken as 811 Ω, taking the arithmetic averagecalculated from the resistivity of each meter depth.

Z=4.3. Fall of potential and step-voltage measurements

Vmax
Imax

(1)

5. Energy dissipation due to step and touch-voltage drop

Each electrode setup underwent a standardized FoP test [22] for both
low-frequency signals generated by a digital earth tester and a lightning
signal from the combined wave generator. The earth system resistance isdetermined at the point approximately 62 % of the distance between thetwo outermost electrodes. The same ground pegs utilized in the test were
employed to measure the step voltage drop between each pair of pegs.
Consequently, step voltage measurements were carried out at one-meterintervals along a straight line originating from each electrodeThe energy transferred during exposure to lightning current can becalculated by multiplying the action integral with body resistance [2],making standard electrical energy equations applicable, including Eq.
(2) below;∫
1
Estep/touch =V(t)2 .dt
(2)
RH

Fig. 3. Experimental instrument arrangement (a) FoP test (b) Step -voltage test.
3

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Electric Power Systems Research 231 (2024) 110330

Fig. 4. Typical current and voltage signal used in the experiment.

In a step-voltage test, the voltage drop between two pegs canrepresent the voltage difference experienced by a person standing along
the current flow path. This measured voltage can be used in Eq. (2) tocalculate the energy dissipation due to step-voltage with human bodyresistance, typically taken as 1000 Ω [12]. The energy calculated will bereferred to as "step-energy" dissipation within the article.
Touch voltage is the difference in voltage between a person’s handand feet when the hand is in contact with an energized part of an earthed
structure while standing on the ground. Meanwhile, the fall of potential
is the voltage difference between two points on the ground, one on theearthed electrode and the other further away [22]. Consequently, theresults from the FoP assessment can be used to represent touch-voltage
in the experiment. Subsequently, FoP recordings will be used to computethe energy dissipation during exposure to touch-voltage. The resulting
energy dissipation will be denoted as "touch-energy" dissipation within
this article.

Rearth =

]
]
[ ( )
[ ( )
8L
ρ
8L
(ρ1 − ρ2 )− 1 + 2 ln
− 1
ln
2πL
d2
d1
2πL

(4)

Table 2 compares theoretical and measured resistance and imped­
ance values. The reference electrode displays the highest value in all
categories. Like Bentonite, concrete is known to improve earthing per­formance [5,9], and concrete shows the lowest in both measured values
and slightly higher value in the calculated resistance.
6.2. Step-voltage and step-energy dissipation
The highest step voltage was recorded in the first measurement for
all five electrodes. To normalize the step voltage values, each value wasdivided by the maximum value of the respective injected voltage. The
same step-voltage measurements were used to calculate the step-energy
dissipation using Eq. (2). Since the step-energy dissipation is also related
to the injected energy during the test, the calculations were normalized
to unit injected energy before calculating the percentages. The per­centage reduction of each outcome compared to reference electroderesults is presented in Table 3.

6. Data analysis and investigations
An earthing system’s performance is typically accomplished byevaluating its earth impedance, maximum step voltage, and touch
voltage. This study introduces energy dissipation as an additional
effective parameter for appraising earthing system performance. The
analysis includes the determination of earth system impedance, step andtouch voltage, and energy dissipation across four EEC-encased elec­
trodes compared to a reference electrode.

6.3. Touch-voltage and touch-energy dissipation
The touch-voltage was investigated at the 15th measurement fromthe earth electrode. This measurement corresponds to approximately 62% of the distance between the current injection and auxiliary electrodes.
Table 4 illustrates the comparison between the reduction in touchvoltage and touch-energy dissipation as a percentage of reference elec­
trode results. Similar to the previous calculation, all the values werenormalized to the maximum relevant injected voltage and the injectedenergy dissipation before calculating the percentage reduction.

6.1. Fall of potential test and earth impedance
The FoP test was used to calculate both the low frequency and im­
pulse Impedance of each grounded electrode. The earth resistancevalues were directly measured using the digital earth resistance tester,while impedance was calculated from Eq. (1). Eqs. (3) and 4 [24] areused for comparative purposes to calculate each electrode’s theoreticalearth resistance.
For single vertical electrodes without EEC,
]
[ ( )
ρ
8L
Rearth = 1 ln
− 1
(3)
d
2π L

Table 2
Resistance and impedance comparison of EEC-enhanced electrodes.

For single vertical electrode with EEC;

4

Material

Resistance (Ω)

Impedance Z (Ω)

Theoretical resistance (Ω)

Reference
Concrete
Bentonite
EEC 1
EEC 2

671.6
164.8
341.6
258.1
196.5

330.6
200.9
220.9
212.0
206.3

580.8
386.0
384.0
383.6
383.6

L. Chandimal et al.

Electric Power Systems Research 231 (2024) 110330

mitigating step voltage-related hazards.

Table 3
Percentage reduction in step-voltage and step-energy dissipation compared toreference electrode results.
Electrode% decrease in step-voltage
compared to the referenceelectrode% decrease in step- energy
compared to the referenceelectrode

Referencerod
Concrete
Bentonite
EEC 1
EEC 2

–

–

18.6
41.0
81.9
97.6

30.2
55.8
91.5
96.5

7.2. Touch-voltage and energy dissipation
Considering the preceding measurements and computations, incor­
porating any EEC results in an improved performance compared to using
the electrode alone without any such enhancement. This pattern issimilarly observed in the touch voltage calculations, as illustrated inTable 4, where using concrete and Bentonite as EECs leads to nearly
equivalent reductions in touch voltage. However, in touch-energy cal­culations, the bentonite-encased electrode unexpectedly demonstrates
higher energy dissipation, even surpassing the outcomes of the referenceelectrode by 100 %.
Despite this unanticipated behavior from Bentonite, both concreteand two commercial EECs still exhibit a significant reduction in touchenergy dissipation. No existing literature reports a similar phenome­
non of EECs resulting in weaker earth system performance. Therefore,
an additional 23 FoP measurements were conducted, employing similarcalculations to explore this observation further. The results consistently
revealed the elevated energy dissipation by the Bentonite-encased
electrode. The dissipation of touch-energy from the first and tenthmeter measurements is illustrated in Figs. 5, using a bar graph.
To investigate deeper into the cause of this behavior, measured andinjected voltage signals were compared across all electrode configura­tions. The rest of the analysis focused on the current and voltage signals
collected at the 15th measurement. Fig. 6 presents both injected andmeasured touch voltages for all five electrodes. As shown in Fig. 6a, allfive injected voltage signals exhibit near-identical waveforms, largely
overlapping one another. Contrastingly, Fig. 6b reveals distinctive var­iations in the measured touch voltage signals. Notably, the areas underthe bentonite curve are unmistakably greater, directly corresponding to
the calculated higher energy levels. Figs. 6c and 6d provide a closer
examination of these signals within a shorter timeframe.

Table 4
Percentage reduction in touch-voltage and touch-energy dissipation compared
to reference electrode results.
Electrode% decrease in touch-voltage
compared to the referenceelectrode% decrease in touch- energy
compared to the referenceelectrode

Referencerod
Concrete
Bentonite
EEC 1
EEC 2

–

–

27.5
24.4
39.3
27.8

78.1
− 101.4
66.7
66.9

7. Discussion
While earth impedance or resistance is often used to estimate anearthing system’s effectiveness, reaching a consensus between various
measured or calculated values in real-world applications can be difficult.
Although the impedance and resistance values outlined in Table 2 differ
in terms of absolute values, their order of magnitude is consistent,
excluding theoretical calculations. The primary cause of the discrepancy
between theoretical and measured values lies in the linear dependenceof the equations on resistivity values. These resistivity values may notaccurately represent the true soil or EEC characteristics in terms of theirimpact on earth resistance/impedance. However, the findings are
consistent with existing literature, indicating that concrete marginallyoutperforms Bentonite [5,6]. The evaluation of two tested commercial
products reveals similar earth resistance and impedance performance.
Consequently, a more robust practical measurement technique wasimperative to assess the effectiveness of an earthing system. Findings
from both step and touch voltage studies demonstrated that earth
resistance or impedance alone is insufficient for evaluating the effi­
ciency of an earthing system.

7.3. Frequency variation of earthing impedance
The slow decay of the voltage signal produced by the Bentonite
encased electrode seen in Fig. 6b can be attributed to the high capacitive
nature of the electrode system. All earthing arrangements exhibit slightcapacitive behavior, as evidenced by the leading current signal relative
to the voltage signal, as seen in Fig. 4. To further investigate this
response, the complex earthing impedance Z(ω) was calculated by
dividing the voltage phasor V(ω) by the current phasor I(ω) obtained
after applying the Fast Fourier Transform (FFT) to the signals [25].
Fig. 7 shows the complex earthing impedance and phasor plots foreach electrode arrangement. All earth rods exhibit an approximately
constant impedance at low frequencies. While having different values,
the same order of magnitudes displayed in Table 2 was seen in thecalculated complex impedance. With the increased frequency, a mar­
ginal impedance drop was seen in the Bentonite-encased electrode.
Analysis of the phase angle plot indicates that the cause of the imped­
ance decline with increasing frequencies could be due to the significant
capacitive nature of the electrode, as evidenced by the substantial
reduction in the phase angle. In addition to the Bentonite-encased
electrode, the reference rod shows a significant decrease from a posi­tive phase angle. This observation and the fact that both electrodes
exhibit the highest energy dissipation in Fig. 5 suggests that the capac­
itive behavior probably plays a significant role in energy dissipation
described in previous discussions.
The increased capacitive behavior can further be extended to thedielectric permittivity inherent in each material. In the case of pure
Bentonite, the dielectric permittivity is approximately 600 at around 1
MHz frequency, progressively increasing with decreasing frequency toabout 800 at 1 kHz [26]. In comparison, the dielectric constant for
concrete is roughly 150 at 1 MHz, as documented in [27]. Furthermore,
Bentonite exhibits superior moisture absorption capabilities compared7.1. Step-voltage and energy dissipation
Exposing to step voltage usually does not result in fatality forhumans, as the current typically enters through one leg and exits
through the other, safeguarding vital organs. Nevertheless, it could
present a potential risk of electric shock and subsequent injuries due toindirect consequences. With respect to step voltage and step-energy
dissipation, Table 3 exhibits a consistent order across all five elec­
trodes. The reference electrode displays the highest values, and the twocommercial EECs display the lowest values. Experimentally, it showsthat step-voltage signal peak value and step-energy dissipation have animperfect linear relationship.
While concrete exhibits superior performance in impedance,
Bentonite outperforms concrete in terms of step voltage and step-energy
dissipation. Specifically, Bentonite reduces over 50 % in step-energy
dissipation compared to the reference electrode. Interestingly, twocommercial EECs, which demonstrated moderate performance in
impedance calculations, display a remarkable reduction of over 90 % instep-energy dissipation. This positions them as the safest option in5

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Electric Power Systems Research 231 (2024) 110330

Fig. 5. Touch-energy and relevant injected Energy dissipation (a) and (b) 1st meter measurement, (c) and (d) 10th meter measurement (R, C, B, E1 and E2 represent
Reference, Concrete, Bentonite, EEC1 and EEC2 respectively).

Fig. 6. Measured touch-voltage and injected voltage signals for all five earth rods for 15th FoP measurement – (a) and (b) for long time span, (b) and (c) for shorttime span.

to concrete, further enhancing its dielectric constant [28]. Conse­
quently, this leads to increased capacitance in the Bentonite-encased
earth rod configuration, subsequently slowing the voltage signal’s
decay and resulting in greater energy dissipation.
As observed with Bentonite encased electrode, lower earth resis­
tance, and higher energy dissipation introduce a risk of potentially
underestimating the risk of real exposure to touch voltage. In order toarrive at conclusive results, it is necessary to investigate deeper into thedielectric properties of these EECs and the distinctive attributes of therelevant part of the soil. However relying solely on a conventional touch
voltage value might prove insufficient in evaluating the risk of touch
voltage exposure. The unexpected outcomes seen in the touch-energy
dissipation of Bentonite were undetected in the step-energy

calculations and in time domain impedance measurements.
8. Conclusions
Four earth electrodes encased in concrete, Bentonite, and two com­
mercial Earth-Enhancing-Compounds (EECs) were tested compared to areference electrode responding to an impulse signal. The purpose was toassess the impact of these materials on earth impedance and the step andtouch voltages. The results indicated that applying EECs notably
decreased earth impedance for both steady-state and impulse signals.
Concrete yields slightly better earth impedance than Bentonite undersimilar conditions, supporting the existing literature.
In terms of step and touch voltages, all EECs significantly reduce6

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Electric Power Systems Research 231 (2024) 110330

Fig. 7. Complex earthing impedance Z(ω) diagram for all five earth rods (15th FoP measurement).

Data availability

exposure compared to the peak values of impulse signals. However, thecomputation of dissipated energy during exposure to step and touch
voltages indicates that relying solely on the impulse signal’s peak value
is inadequate when EECs are used. Further, step-energy dissipation andpeak step voltage values exhibited similar trends in magnitude ranking.
No such correlation was observed for touch voltage and corresponding
touch-energy calculations.
Interestingly, using Bentonite as an EEC resulted in an unexpected
outcome. The dissipation of energy calculated from touch voltage
measurements for bentonite-encased electrodes was higher compared tothat of reference electrode results. This counterintuitive result persisted
even though Bentonite demonstrated notably improved earth imped­
ance as well as step and touch voltage values. This finding was further
confirmed by additional measurements. As a result, this field study
suggests that Bentonite has the potential to increase the risk of touch
voltage-related injuries.
An earthing impedance analysis in the frequency domain provides
evidence of the strong capacitive nature of Bentonite which probably
causing the higher energy dissipation. Consequently gaining a deeper
understanding of the dielectric properties of materials and the effective
soil properties at the site would contribute more insights into theseoutcomes. The introduction of energy-based calculations to step andtouch voltage measurements presents a more dependable approach toanalyzing potential risks associated with the performance of earthing
systems.

Data will be made available on request.
Acknowledgements
This work was partially funded by the National Research Council, Sri
Lanka, (NRC 15–32). The authors gratefully acknowledge the use ofservices and facilities of the Department of Physics, University ofColombo, Sri Lanka. Additionally, the authors would like to recognize
the Society for Lightning Protection & Research Development (SLPRD) Sri Lanka for their contributions in terms of both funding and techno­
logical aid.
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CRediT authorship contribution statement
Lasantha Chandimal: Conceptualization, Methodology, Writing –original draft. Manoj Rajakaruna: Investigation. Sankha Nanayak­
kara: Investigation. Sidath Abegunawardana: Investigation. Mahen­
dra Fernando: Writing – review & editing, Supervision, Funding
acquisition. Vernon Cooray: Supervision.
Declaration of competing interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.

7

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