Soil Treatment to Reduce Grounding Resistance by Applying Low-Resistivity Material (LRM) Implemented in Different Grounding Systems Configurations and in Soils with Different Resistivities
, Cristian Coronel-Naranjo †, Antonio Barragán-Escandón * and Flavio Quizhpi-Palomeque *Round 1
Reviewer 1 Report
1. The quality of Figures should be improved. They are not visible enough to a readers.
2. Equations and corrseponding assumption related to analyzed GS geommetries should be explicitely given. Related to this, there is a question: Are conducting wires (which connect rods of GS) assumed as isolated or non-isolated. ?
Author Response
Dear reviewer, thank you for your suggestions:
- The quality of Figures should be improved. They are not visible enough to a readers.
The size of the figures has been modified.
- Equations and corrseponding assumption related to analyzed GS geommetries should be explicitely given. Related to this, there is a question: Are conducting wires (which connect rods of GS) assumed as isolated or non-isolated. ?
The equations used in this study were added. On the other hand, the conductors used to connect the GS rods are bare copper, as mentioned in section “3.3. Step 3: Implementation of GS designs” - The #4 AWG stranded bare copper conductor was buried at a depth (h) of 0.25 m. Therefore, they are not isolated.
Reviewer 2 Report
The paper is well-written and well-presented. I, therefore, accept it in its current form.
All the best
Author Response
Dear reviewer, we thank you for your kind comments.
Reviewer 3 Report
Overall, the paper is correctly written, measurements and analyses have been performed (although limited!), but the scientific contribution and novelty of the manuscript are flawed or insignificant. The authors need to clearly identify the significance of their contribution.
1. Line 32-36: The authors wrote that IEEE 80-2013 in focused on safe grounding and it requires calculating tolerable step and touch voltages, however this is not required for distribution systems.
I do not agree with that statement! Please clarify the above.
2. The authors refer to (and cite) some IEEE standards that are inactive, i.e. withdrawn.
3. The authors cite a number of references in the paper, which are not in English (which is not very common), and also have duplicates [19] = [35].
4. References not updated. There are many recent papers in prestigious journals that deal with this issue, which are not listed in this paper.
5. Theoretical framework given in chapter 2 is well-known, while experimental research (chapter 3) is research is significantly limited (resistivity values are low, only 1-300 Ωm, although for the latter the authors state that it is a high value).
The low-resistivity material (LRM) is widely used to decrease the power-frequency grounding resistances of grounding devices for transmission lines in the regions with high soil resistivity.
6. The paper does not list any of the formulas used for GR calculations, only that they are taken from the IEEE standard (one of which has been withdrawn!).
7. Line 144: The authors wrote "In the present project, premixed and dry LRMs were used [5].".
It’s a work with the same first author, the structure is very similar, even the title of the paper itself, so I’m interested in what’s new in this paper and what the real scientific contribution, if any, is.
8. Some sentences from the analysis and discussion, as well as the conclusions, are too simple, and this was to be expected (e.g. as the complexity of the GS design (or soil resistance) increased, the reduction in the GR of the LRM decreased), which even the authors state that this corresponds to the results of other studies.
Author Response
Overall, the paper is correctly written, measurements and analyses have been performed (although limited!), but the scientific contribution and novelty of the manuscript are flawed or insignificant. The authors need to clearly identify the significance of their contribution.
Dear reviewer, we thank you for your kind and sincere comments.
- Line 32-36: The authors wrote that IEEE 80-2013 in focused on safe grounding and it requires calculating tolerable step and touch voltages, however this is not required for distribution systems.
I do not agree with that statement! Please clarify the above.
Thank you for your observation, the manuscript was modified according to "Annex G" of the IEEE 80-2013 standard.
“While the grounding systems may be adjusted to eliminate dangerous contact potentials by suppression of ground short-circuit currents, this is not usually demanded of solidly grounded neutral systems because it does not appear to be practicable. For ground-fault currents above 1000 A, grounding systems of vast dimensions must be installed in order to meet the usual 125 V contact potential requirement.”
- The authors refer to (and cite) some IEEE standards that are inactive, i.e. withdrawn.
Answer: Thank you for your observations. IEEE standard 665-1995 has been removed.
Answer: Replaced the IEEE 142-2007 standard reference with the reference to the article called “Calculation of Resistances to Ground” by H. B. Dwight. This is because the Dwight equation for calculating the resistance of a rod in vertical arrangement was referenced through the IEEE 142-2007 standard; however, the equation's author's article is now referenced.
- The authors cite a number of references in the paper, which are not in English (which is not very common), and also have duplicates [19] = [35].
Fixed duplicate reference. In addition, other references were added.
- References not updated. There are many recent papers in prestigious journals that deal with this issue, which are not listed in this paper.
Thank you for your comments. The following references on the subject matter were added to the manuscript:
[34] W. F. H. Wan Ahmad, N. H. Hamzah, J. Jasni, M. Z. A. Ab-Kadir and C. Gomes, "A Study on Bentonite and Kenaf Properties for Grounding Purposes," 2018 34th International Conference on Lightning Protection (ICLP), 2018, pp . 1-8, doi: 10.1109/ICLP.2018.8503361.
[35] S.k. Ahmad, R. Z. Sabry and C. Gomes, "Improving the Grounding System by Adding Bentonite to Reduce the Potential Distribution," 2021 International Conference on Electrical, Communication, and Computer Engineering (ICECCE), 2021, pp. 1-5, doi: 10.1109/ICECCE52056.2021.9514191.
- Theoretical framework given in chapter 2 is well-known, while experimental research (chapter 3) is research is significantly limited (resistivity values are low, only 1-300 Ωm, although for the latter the authors state that it is a high value).
The low-resistivity material (LRM) is widely used to decrease the power-frequency grounding resistances of grounding devices for transmission lines in the regions with high soil resistivity.
This study is limited to eight fields with different soil resistivity (up to 300 Ωm) due to the high cost and difficulty of the materials involved, tests and field measurements.
Another factor to consider is that SPTs rely heavily on copper. Due to its scrap value, copper is an attractive material in the irregular trade. To avoid theft and vandalism of the materials used, field tests are carried out in rural areas of the city of Cuenca-Ecuador, where the authors can keep the materials protected during the course of this study.
Although it is true that the study is limited, later this study has facilitated the calculation of the Earthing Resistance by applying LRM, varying the length of the rod, the radius of the rod, the gauge of the conductor, the distance between rods, the burying depth of the conductor, among others. This up to 300 Ωm. Subsequent or complementary studies with higher resistivity terrains can be used to extend the calculation of the grounding resistance by modifying the mentioned variables.
In addition, the following was added in the conclusions section:
“Through the formulation of section 3.4, the grounding resistance can be calculated by modifying the different variables involved, and later, depending on the design chosen, apply the reduction percentage when LRM is applied to the vertical rods. Thus obtaining the calculation and design of the grounding mesh with LRM; the higher the resistivity, the greater the number of rods and conductor wire can be reduced. Although it is true that Table 12 is limited to 250 Ω m, the study can be extended to soils with higher resistivity, achieving a greater percentage reduction in grounding resistance (GR), and above all relating the grounding configurations land with the theoretical calculation. Likewise, additional studies could be carried out by implementing LRM in the conductor cable buried horizontally, taking into account that this would require significant financing.”
- The paper does not list any of the formulas used for GR calculations, only that they are taken from the IEEE standard (one of which has been withdrawn!).
The formulas used in this work were added.
As noted above, the IEEE 142-2007 reference to the calculation of resistance of a rod in a vertical arrangement has been replaced by the article called “Calculation of Resistances to Ground”.
- Line 144: The authors wrote "In the present project, premixed and dry LRMs were used [5].".
It’s a work with the same first author, the structure is very similar, even the title of the paper itself, so I’m interested in what’s new in this paper and what the real scientific contribution, if any, is.
In the cited work, field tests were carried out with random configurations. This is due to the fact that the formulation for calculating the Grounding Resistance with common materials for simple configurations was not available. And the result of the MRLs was totally unknown. Therefore, it was not possible to check with the theoretical calculation,
With the present study, it is already possible to calculate the value of the grounding resistance by applying LRM, either by modifying the grounding configuration (up to a connected grid of 6 rods), the length of the rod, the radius of the rod, the gauge of the conductor, the distance between rods, the depth of the conductor's burial, among others, as mentioned above.
Having a mobile application and a spreadsheet that facilitates the researcher to design the grounding system with LRM to obtain the desired grounding resistance.
The final result of this article is limited to the table of reduction percentages with LRM. With it, different grounding designs can be calculated using LRM.
For this reason the following was added to the manuscript:
Discussion: “As mentioned above, most studies with LRM are isolated and small scale, that is, they present results for a single configuration, in a single terrain of a given resistivity, and do not relate the results to the theoretical calculation. Single GR reduction percentages with LRM may confuse the reader, implying that these percentages are given for any configuration and in any soil of different resistivity. On the other hand, this study presents different configurations, terrains with different resistivity values, relationship with the theoretical calculation, and above all, field tests and measurements are carried out; resulting in different values of grounding resistance reduction (see table 12)”
Conclusions: “Through the formulation of section 3.4, the grounding resistance can be calculated by modifying the different variables involved, and later, depending on the design chosen, apply the reduction percentage when LRM is applied to the vertical rods. . Thus obtaining the calculation and design of the grounding mesh with LRM; the higher the resistivity, the greater the number of rods and conductor wire can be reduced. Although it is true that Table 12 is limited to 250 Ω m, the study can be extended to soils with higher resistivity, achieving a greater percentage reduction in grounding resistance (GR), and above all relating the grounding configurations land with the theoretical calculation. Likewise, additional studies could be carried out by implementing LRM in the conductor cable buried horizontally, taking into account that this would require significant financing.”
- Some sentences from the analysis and discussion, as well as the conclusions, are too simple, and this was to be expected (e.g. as the complexity of the GS design (or soil resistance) increased, the reduction in the GR of the LRM decreased), which even the authors state that this corresponds to the results of other studies.
This study is intended as a guide for the calculation and design of a grounding with LRM. Although it is true, there are previous studies on the application of LRM, these are not related to the calculation of the grounding resistance. With this study, the grounding resistance can be calculated in various configurations when LRM is applied to the vertical rods. Therefore, the following text is previously placed in the discussion:
Discussion: “In this study, various GS configurations were implemented (see Figure 1). These configurations were chosen mainly because they make it possible to compare measured GR values
with calculated GR values. Such a comparison is very useful because the GR performance can be assessed by installing LRMs in each of the vertical rods. In the literature there are field tests applying LRM in different configurations, but on a reduced scale, where the GR results could not be related to the existing formulation when another type of grounding mesh is required, even more so when it is required calculate the GR by modifying the formulation variables (see the formulation and its respective variables in 3.4); for example, [30 ] installed a 2 m x 2 m grid in three soils with different resistivities. [31 ] installed five individual rods in each of five soils with different resistivities, and [ 32 ] used three cylindrical rods with the same length (l = 50 cm) but different diameters.”
In addition, the study can be extended by increasing the resistivity of the soil. The configurations, implementations, field measurements, etc., were not carried out randomly in order to measure the behavior of LRM and the process is finished, on the contrary, the purpose is that through the study the variables of the formulation and it is known what will be the result of the grounding resistance by modifying configurations, and all the variables that are observed in the formulation (This was added in the section: conclusions).
Reviewer 4 Report
The authors present results of field tests (measurements) with the objective of reducing low-frequency resistance of different electrical grounding configurations. Such a reduction is achieved using low-resistivity materials. Additionally, the effectiveness of low-resistivity materials is evaluated as the complexity of grounding systems is increased.
The article is relatively well written and very well organized. The methodology adopted seems to be quite adequate, as the objectives initially established were achieved in view of the results obtained.
The theme studied in the article is of great interest to the area of electrical protection engineering. However, it is not properly characterized in the article what is the main (original) contribution provided by the article in the study of art in this theme. It is of fundamental importance that the authors present this question in a “forceful way”.
Furthermore, this reviewer considers it important that authors include the following considerations in the article:
1) only one parameter that characterizes the low-frequency grounding behavior is considered in the article, namely, the low-frequency resistance. However, the grounding potential rise (GPR) is very important under these conditions. Thus, I think that the authors should justify in the article the fact that they do not address this important magnitude.
2) added to item 1), the article deals only with the electrical grounding behavior in the face of low-frequency phenomena. Thus, the results cannot be extended to situations in which the grounding is subjected to high-frequency phenomena, such as lightning. Thus, it is important that the authors highlight the premises of the presented study, in such a way that its limits of validity are well established.
Author Response
Dear reviewer, we thank you very much for your sincere comments. And we hope that our answers know how to answer his suggestions.
The authors present results of field tests (measurements) with the objective of reducing low-frequency resistance of different electrical grounding configurations. Such a reduction is achieved using low-resistivity materials. Additionally, the effectiveness of low-resistivity materials is evaluated as the complexity of grounding systems is increased.
The article is relatively well written and very well organized. The methodology adopted seems to be quite adequate, as the objectives initially established were achieved in view of the results obtained.
The theme studied in the article is of great interest to the area of electrical protection engineering. However, it is not properly characterized in the article what is the main (original) contribution provided by the article in the study of art in this theme. It is of fundamental importance that the authors present this question in a “forceful way”.
With the present study it is possible to calculate the value of the grounding resistance by applying LRM, either by modifying the grounding configuration (up to a connected grid of 6 rods), the length of the rod, the radius of the rod, the gauge of the conductor, the distance between rods, the depth of burial of the conductor, among others.
With them, it facilitates the grounding design with LRM, to obtain the desired grounding resistance.
Furthermore, this reviewer considers it important that authors include the following considerations in the article:
- only one parameter that characterizes the low-frequency grounding behavior is considered in the article, namely, the low-frequency resistance. However, the grounding potential rise (GPR) is very important under these conditions. Thus, I think that the authors should justify in the article the fact that they do not address this important magnitude.
Thank you for your observation, the manuscript was modified according to "Annex G" of the IEEE 80-2013 standard.
“While the grounding systems may be adjusted to eliminate dangerous contact potentials by suppression of ground short-circuit currents, this is not usually demanded of solidly grounded neutral systems because it does not appear to be practicable. For ground-fault currents above 1000 A, grounding systems of vast dimensions must be installed in order to meet the usual 125 V contact potential requirement.”
Immediately in the manuscript the following is indicated:
“The grounding configurations of this study are designed for fault currents less than 1000 A.”
- added to item 1), the article deals only with the electrical grounding behavior in the face of low-frequency phenomena. Thus, the results cannot be extended to situations in which the grounding is subjected to high-frequency phenomena, such as lightning. Thus, it is important that the authors highlight the premises of the presented study, in such a way that its limits of validity are well established.
It should be noted that the study can be extended, today there is equipment such as the MRU-200-GPS digital meter, with which the grounding resistance can be measured with the impulse method, making measurements with three forms of impulse (T1 /T2):
- 4μs/10μs.
- 8μs/20μs.
- 10μs/350μs.
The submitted manuscript does not involve high-frequency phenomena as you mention (such as lightning), this would obviously lead to the maintenance of the grounding mesh since LRM would lose its conductivity properties.
These events are not mentioned in this manuscript since the reduction of LRM has been established primarily in different grounding configurations and in terrains with different resistivity values, to finally relate the results with the existing formulation.
Round 2
Reviewer 3 Report
The authors have improved the paper and therefore it can be published in the journal Applied Sciences.
Note: the size of Figures 8-18 could be increased to make them more visible.
Author Response
Dear reviewer, we thank you for your approval and suggestions.
The sizes of Figures 8-18 have been increased.
Reviewer 4 Report
I think the authors have adequately answered my question. Furthermore, the article was, in my opinion, improved with corrections. In this way, the article is ready to be published.
Author Response
