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:

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 explained Methods of Grounding Design Calculations of Domestic, commercial and industrial premises in the following Articles:
 Grounding Design Calculations – Part One and Grounding Design Calculations – Part Two: Equations Method and solved examples.
 Grounding Design Calculations – Part Three: Nomographs Method
 Grounding Design Calculations – Part Four: Excel Spreadsheets Method
 Grounding Design Calculations – Part Five and Grounding Design Calculations – Part Six: using Tables Method
 Grounding Design Calculations – Part Seven and Grounding Design Calculations – Part Eight: Using Online Earthing Calculators
 Grounding Design Calculations – Part Nine: Software Programs Method
Second: High And Medium Voltage Electricity AC Substations

I began explaining Grounding Design Calculations for second type of buildings: AC Substations in Article " Grounding Design Calculations – Part Ten " where I explained the following:
 Design Procedures for grounding system design as per IEEE 80: Guide for safety in AC substation grounding,
 Step#1: Field Data Collection,
 Step#2: Earthing Grid Conductor Sizing.
Grounding Design Calculations – Part Twelve: Step#4: Preliminary Design of Grounding System for AC Substations.
Grounding Design Calculations – Part Thirteen: Step#5: Calculation of the Preliminary Grid Resistance, Rg, Of the Grounding System in Uniform Soil.
Grounding Design Calculations – Part Fifteen, I explained the following steps:
 Step#7: Calculation of Maximum Grid Potential Rise and Comparing With the Tolerable Touch Voltage from Step#3
 Step#8: Calculation of Mesh and Step Voltages
Grounding Design Calculations – Part Sixteen, I explained the following steps:
 Step#9: Comparing The Computed Mesh Voltage From Step#8 With The Tolerable Touch Voltage From Step#3
 Step#10: Comparing The Computed Step Voltage From Step#8 With The Tolerable Step Voltage From Step#3
 Step#11: Preliminary Design Modification
 Step#12: Detailed Final Design
You can preview the following Articles for more info:
Excel Spreadsheets for Grounding System Design
Calculations of AC Substation

Today, I will introduce to you, the most powerful
excel spreadsheet for Grounding System Design Calculations of AC Substation.
Important
Use
this excel spreadsheet for AC Substation only, and don’t use it for Domestic,
commercial and industrial premises.
(Please review the above definition for domestic, commercial and industrial
premises).
Another
excel spread sheet was provided for Grounding System Design Calculations for Domestic, commercial and industrial premises. Just follow the Link.

Benefits For Using This Excel Spreadsheet

This excels spreadsheet includes (5) nos. worksheets and (9) nos. pages (see below image) as follows:
S/N

Worksheet Name

No. of Pages

1

Table Of Contents

1

2

Design Procedure Block Diagram

1

3

Grounding System Calculations

5

4

Results Summary Report

1

5

Used Tables

1

Total

9

Excel Spreadsheets for Grounding System Design Calculations of AC Substation 
First: Table of Contents Worksheet
Table of Contents Worksheet 
This worksheet lists the other worksheets in an index as shown in below figure, you can go to a specific worksheet by just clicking on its name.
You can send email to me directly by clicking on the phrase “Designed by: Ali Hassan” for any inquiries or notes.
Second: Design Procedure Block Diagram Worksheet
You can send email to me directly by clicking on the phrase “Designed by: Ali Hassan” for any inquiries or notes.
Second: Design Procedure Block Diagram Worksheet
Design Procedure Block Diagram Worksheet 
This worksheet includes the block diagram which illustrates the sequences of steps to design the ground grid of AC Substations and it is divided to (2) types of shapes as follows:
Third: Grounding System Calculations Worksheet
This worksheet includes general data that must be known in the starting of Grounding System Design Calculations of AC Substations, which are included in step#1 as follows:
Also, this worksheet helps you to calculate the following:
Fourth: Results Summary Report Worksheet
 Rectangular shapes: for data entering and data calculation,
 Diamond shape: for logical comparison between different values.
Note: The diamond shapes based on their logical answer “yes or no” will
change the calculations sequence i.e. you may continue to next step or you
may move forward or backward to other steps.

Third: Grounding System Calculations Worksheet
This worksheet includes general data that must be known in the starting of Grounding System Design Calculations of AC Substations, which are included in step#1 as follows:
 Soil Resistivity, ρ
 Gravel Resistivity, ρs
 Symmetrical Short Circuit Current, Ig
 Duration of Earth Fault Current, ts
 Maximum Allowable Conductor Temperature
 Design Ambient Temperature
 Thickness of Crushed Gravel, hs
 Depth of Earth Grid, h
 Reference depth of the Grid, ho
STEP#1: GENERAL DESIGN DATA 
Important: The data input cells are the yellow color ones

Important

Also, this worksheet helps you to calculate the following:
 Step#2: The size of the grid conductor in Kcmil, mm2 and its diameter
 Step#3: Tolerable touch voltage and step voltages (Etouch and Estep)
 Step#5: Grid resistance calculation, Rg
 Step#6: Maximum Grid Current calculation, IG
 Step#7: Ground Potential Rise GPR
 Step#8: Calculation for Actual Derived Step & Mesh Voltage (Es and Em)
Note: The default of this excel sheet for Tolerable touch voltage and step
voltages in Step#3 was made for 70 Kg persons, if there is a need to
calculate for 50 Kg persons, just send email to me as a modification request.

Important: The data Results cells are the Pink color ones

For Step#4: Initial Design Assumptions
This step depends on the experience of the designer to provide good initial design parameters that suit the case under design, for more information about this step and how to assume its data, please review our Article " Grounding Design Calculations – Part Twelve ".

Step#5: Grid resistance calculation 
Step#6: Maximum Grid Current calculation 
In addition to the above, this worksheet helps you to logically compare between the different designs parameters as follows:
 In Step#7: comparing the computed GPR with the Tolerable Touch Voltage from Step#3,
 In Step#9: Comparing the Computed Mesh Voltage from Step#8 with the Tolerable Touch Voltage from Step#3,
 In Step#10: Comparing the Computed Step Voltage from Step#8 with the Tolerable Step Voltage from Step#3.
Important: The results of the logical comparison for the above (3) steps are
included in the yellow cells between brackets.

Step#8: Calculation for Actual Derived Step and Mesh Voltage 
Fourth: Results Summary Report Worksheet
Results Summary Report Worksheet 
This worksheet gives results summary under three sections as follows:
Section#1: Earth Grid Conductor, it gives:
 Type of Conductor,
 Size of Conductor,
 Length of Conductor,
 Depth of Conductor.
Section#2: Ground Rods, it gives:
 Total Length of Ground Rods,
 Length of Individual Ground Rods,
 No. of Ground Rods.
Section#3: Human Safety, it gives:
 The permissible (Tolerable) values of the touch and step voltages,
 The designed value of the touch and step voltages,
 The result of logical comparison between the Computed Mesh Voltage from Step#8 with the Tolerable Touch Voltage from Step#3,
 The result of logical comparison between the Computed Step Voltage from Step#8 with the Tolerable Step Voltage from Step#3.
Fifth: Used Tables Worksheet
Used Tables Worksheet 
This worksheet includes the used table in calculations which is Table1 for grid conductor Material Constants. This table is extracted from standard IEEE 802000, page 42.
The Material Constants provided by Table1 are as follows:
 Material conductivity (%)
 αr factor at 20 °C (1/°C)
 Ko at 0 °C (0 °C)
 Fusing temperature Tm (°C)
 ρr 20 °C (μΩ·cm)
 TCAP thermal capacity [J/(cm3·°C)]
And the grid conductor materials will be as indicated in above Grounding System Calculations worksheet.
To download your copy of Excel Spreadsheet For Grounding System Design Calculations Of AC Substation, please click on the link.
Note:
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In the next Article, I will explain Lightning Design Calculations. Please, keep following.
Ali
ReplyDeleteThe building grounding spreadsheet looks great. However you have used various formulas and there is no reference to any of the formulas. Would you be able to explain where the formulas were taken so that we understand it better.
Regards
SK