Grounding Design Calculations – Part Four


I indicated that the Earthing Systems Design Steps process has (3) main steps:




Earthing Systems Design Steps

A grounding system design process has (3) main steps:
  1. Data Collection,
  2. Data Analysis,
  3. Grounding Design Calculations.



And I explained the first step: Data Collection in the following Articles:



I explained the second step: Data Analysis in the following Articles:


And I explained What we are going to design for grounding system in any building in the following Articles:



And, in Article " Grounding Design Calculations – Part One ", I indicated the following:





Grounding System Design Calculations according to type of the building

The procedures for performing the Grounding System Design Calculations can differ slightly according to the type of the building as follows:

  1. Domestic, commercial and industrial premises,
  2. High and medium voltage electricity substations.





First: Domestic, commercial and industrial premises

We mean by domestic, commercial and industrial premises, all installations up to 1,000 V ac and 1,500 V dc - between phases, with some minor exceptions.


And I started discussion for Methods of Grounding Design Calculations of Domestic, commercial and industrial premises as follows:





Methods of Grounding Design Calculations

There are many methods can be used for performing Grounding System Design Calculations But the common methods are:

  1. Equations Method,
  2. Nomographs Method,
  3. Excel Spreadsheets Method,
  4. Tables Method,
  5. Online Earthing Calculators Method,
  6. Software Programs Method.



In this Article and Article " Grounding Design Calculations – Part Two ", I explained the first method of grounding design calculations: Equations Method and solved examples.


Also, I explained the second method of grounding design calculations: Nomographs Method in Article " Grounding Design Calculations – Part Three".



Today, I will explain the Other Methods for Performing of Grounding System Design Calculations.



You can preview the following Articles for more info:

  







Third Method: Excel Spreadsheets



Today, I will introduce to you, the most powerful excel spreadsheet for Grounding System Design Calculations of Domestic, commercial and industrial premises.


Important

  • Use this excel spreadsheet for Domestic, commercial and industrial premises only, and don’t use it for medium and large electrical substations. (Please review the above definition for domestic, commercial and industrial premises).
  • Another excel spread sheet will be provided later for Grounding System Design Calculations of medium and large electrical substations.





Excel Spreadsheet For Grounding System Design Calculations Of Domestic, Commercial And Industrial Premises





why Using This Excel Spreadsheet

I recommend all electrical engineers to use this powerful excel spreadsheet because it has the following unique advantages than other similar ones:

  1. List all data that must be known in the starting of Grounding System Design Calculations for Domestic, Commercial and Industrial Premises like electrical utility data,
  2. List typical Values of Resistivity from BS 7430 and IEEE 142,
  3. List all applicable standards for Grounding System Design Calculations for Domestic, Commercial and Industrial Premises,
  4. List acceptable values for Earthing Resistance,
  5. Calculate Soil Resistivity by using ground testers that apply The Wenner 4-Point Method,
  6. Provide a professional design concept for any Grounding System,
  7. List the Steps for Choosing the Best Earthing System,
  8. Provide grounding installation criteria for earth electrodes, earth pit, ground buses, grounding conductors, grounding of switches/ panels/ boxes/ cable trays / conduits and special grounding for high tension cables/ control cables /static electricity,
  9. Make (12) nos. different calculations for different cases, shapes and types of earth electrodes,
  10. Help you to specify all materials selected by grounding design process like Grounding conductors, Grounding stations and buried grounding mains,
  11. You can Print it as a professional calculations report for grounding system design for Domestic, commercial and industrial premises.




Excel Spreadsheet Construction:


This excels spreadsheet includes (6) nos. worksheets and (22) nos. pages as follows:

S/N
Worksheet Name
No. of Pages
1
Table Of Contents
1
2
General Information
2
3
Grounding Design Concept
1
4
Grounding Installation Criteria
3
5
Grounding System Calculations
5
6
Grounding Specifications
7

Info Pages
3
Total
22




First: Table of Contents Worksheet





  • This worksheet lists the other worksheets in an index as shown in above figure, you can go to a specific worksheet by just clicking on its name.
  • On the other hand, you can return for any worksheet to the table of contents worksheet by clicking on the black box titled “Back to Table of Contents”.




  • You email me directly by clicking on the phrase “Designed by: Ali Hassan” for any inquiries or notes. 



Second: General Information Worksheet




 




 




This worksheet includes all the general data that must be known in the starting of Grounding System Design Calculations of Domestic, Commercial and Industrial Premises, so it includes the following sections:
  • Project Data,
  • Applied Standard and Codes,
  • Electrical Utility Data,
  • Required Earthing Resistance Value,
  • Soil Characteristics,
  • Info Page#1: Typical Values of Resistivity from BS 7430 and IEEE 142,
  • Info Page#2: Calculation of Soil Resistivity by Measurements.


Important

In this worksheet, you will find multi choice check boxes for each item, sometimes you need to check all of them, sometimes not while some items must have one checked box only (one selection only), in this case two or more checked boxes will contradicted with other selections.

Examples for one only checked box:
  • Type Of Project,
  • Design Life Of Facility,
  • Future Uses, Additions, Equipment For Facility,
  • Standards,
  • Required Earthing Resistance Values,
  • Soil Characteristics.



One Checked Box


Examples for two or more checked box:
  • Electric Utility Data.



Multi-checked Boxes






Important

Steps for using Info page#2: Calculation of Soil Resistivity by Measurements are included in the Help Guide below this info page.





Third: Grounding Design Concept Worksheet






This worksheet includes the general criteria that must be followed to determine what will be earthed, the shape and the size of earthing system, so it includes the following sections:
  • Earthing System Include (what parts will be earthed),
  • Function of the Earthing System,
  • Configuration of the Earthing System,
  • Neutral Point Connection to Earth,
  • Earthing System Connection Method,
  • Country Regulations Be Applied.
  • Info Page#3: Steps for Choosing the Best Earthing System




Fourth: Grounding Installation Criteria Worksheet








This worksheet helps you to construct your grounding network in the project under design, it gives you the complete picture for all the items, conductors and accessories that you will need for providing a complete grounding network through the project, so it includes the following sections:
  • Grounding Conductor (items that need a grounded conductor, grounded conductor type, size and identification),
  • Grounding Stations (general criteria for earth electrodes and earth pit),
  • Buried Grounding Mains (locations for Buried grounding main conductors and which parts must be connected to),
  • Grounding Bus (locations for grounding buses, placement and which parts must be connected to),
  • Connections (connections between conductors, terminations to equipment and terminations to columns & rails),
  • Special Grounding (grounding criteria for high tension cables, for control cables and for static electricity),
  • Deemed Grounded (grounding criteria for switches, panels, boxes, cable trays and conduits)





Fifth: Grounding System Calculations Worksheet












This worksheet helps you to calculate the following:

  1. Main Earthing Conductor from BS 7430:2011 and from IEEE std 80,
  2. Earthing rod resistance,
  3. Parallel earthing rods combined resistance,
  4. Earth resistance for three rods at the vertices of an equilateral triangle,
  5. Horizontal strip electrode (circular or rectangular section) resistance,
  6. Combined resistance for parallel earthing strips in straight lengths and connected together at one end only,
  7. Earth resistance for two strips set at right angles to each other meeting at one corner,
  8. Earth resistance for three strips set at 120° meeting at the star point all of equal length,
  9. Earth resistance for four strips set in a cruciform,
  10. Earthing plate resistance,
  11. Earthing resistance for a reinforced concrete foundation footing,
  12. Earthing resistance for an electrode surrounded by an infill of materials (such as bentonite or concrete).






Important

  • The data input cells are the green color ones and the data results cells are the red ones.
  • Some Aqua colored cells are transition cells for final calculations.



Green, Red and Aqua Colored Data Cells





Sixth: Grounding Specifications Worksheet















This worksheet helps you to specify all the earthing system components that you will use to construct the grounding network through the building/project under design, so it includes the following sections:


1- Grounding conductor Specifications
  • For buried grounding main conductor,
  • For grounding bus conductor,
  • For grounding branch conductor,
  • For steel structure,
  • For motors,
  • For metal pipes (not carrying flammable gas or liquids), vessels and tanks.

2- Grounding stations Specifications
  • Rod earth electrode,
  • Earth pit,
  • Conductor.

3- Buried grounding mains Specifications
  • Connections to the earth rods,
  • Connections to the indoor ground bus,
  • Other buried grounding mains.

4- Types of earth enhancement materials




Important

Also, In this worksheet, you will find multi choice check boxes for each item, sometimes you need to check all of them, sometimes not while some items must have one checked box only (one selection only), and in this case two or more checked boxes will contradicted with other selections.





To download your copy of Excel Spreadsheet For Grounding System Design Calculations Of Domestic,Commercial And Industrial Premises, please click on the link.


Note:

non-registered members in Electrical-Knowhow website will not be able to open and use this excel spreadsheet.


To register as a member of Electrical-Knowhow website, do the following:

  1. click on the phrase " Join this site" in left bottom side of the home page, above the images of our members.
  2. after finishing your registration send email to ali1973hassan@yahoo.com, asking for your password and I will send it with email reply.



Notes for downloading our files:

  1. click on the file name that you want to download
  2. a new page will open, don't care about the message "these files are temporary unavailable",
  3. Look in the upper right corner of the page, you will find an arrow point to down, 
  4. click this arrow the download will start automatically.
  5. after downloading, you will need to enter your password again to open the file.



In the next Article, I will explain Other Methods of Grounding Design Calculations. Please, keep following.




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