Earthing system design tool for low voltage installations

Effective design of earthing systems

This simple software tool with auto-mathematical functions was developed using Microsoft Excel. This template provides a technically acceptable computer simulation and yet a low-cost solution to the complex issue of effective design of earthing systems according to the standards BS-7430, IEEE-120 Green Book, and IEC-60364.

Preliminary layout design is to be conducted after deciding the type of earthing electrode. The resistance of earthing must confirm to the minimum requirement. Further investigation of step and touch voltages is to be made to guarantee that they do not exceed the allowable limits.

Nevertheless, if any of the three parameters still do not comply with standard regulations depending on the site soil conditions, alternative means of effective earthing methods must be considered in reducing the total earthing resistance and also the ground surface potential whenever design modification is necessary.

User Guide for the Design Template

This section is prepared to guide the user of the developed template in designing a new earthing system for a through a step-by-step approach as given below:

Step №1

Open the .xlsx file of the template using Microsoft Excel.

Step №2

Select one of the worksheets as described in the tabs below:

The user can select one of the 8 worksheets by clicking on its tab:

1. Procedure Flow Chart: This worksheet includes a proposed step-by-step approach for the design of earthing systems.
2. BS-7430 Resistance: This worksheet incorporates the calculation of earthing resistance for different types of earthing based on BS-7430.
3. BS-7430 Conductor Selection: This worksheet consists of various parameters selection procedure of materials and sizing of earthing electrodes based on BS-7430.
4. IEEE Green Book:This worksheet includes all formulae used for computing the earthing resistance as proposed by IEEE Green Book.
5. IEC 60364: This worksheet consists of sizing and selection of material of earthing conductors as recommended by IEC 60364.
6. Common Methods: This worksheet incorporates the most common earthing methods applicable in Malaysia for electrode sizing and configuration based on selected target resistance and various values of soil resistivity as recommended by the consulting company.
7. Other Methods: This worksheet collects relevant proposed formula proposed in published papers for calculating earthing resistance.
8. Illustrations: This worksheet includes different figures and diagrams for the various configuration and earthing types.

Step №3 – Calculations of Earthing Resistance

The user can calculate the earthing resistance using the template by selecting the preferred method or standard described as follows:

1. BS 7430 Resistance Calculation
2. Common Method
3. IEEE Green Book
4. Other Methods

Where:

1. The user needs to click on the downward arrow of the drop-down to select one type of earthing by clicking on the text as highlighted in blue

Where:

1. The user needs to enter valid values in the highlighted orange cells for the corresponding parameters described on the left for each parameter. These cells can be manipulated or modified by the user.
2. The user can obtain the result from the grey cell for the earthing resistance for the earthing system chosen previously.

Where:

1. The user needs to select the type of earthing from the drop-down list.
2. The user then needs to enter valid values of the respective input parameters in the cells of orange background.
3. The result of calculated resistance to earth can be obtained from the grey cell.
4. Remarks to inform the user of important design step are shown.

Where:

1. The user needs to select one type of the most common earthing practices from the drop-down list.
2. The user then needs to select the target resistance to be achieved in the design, the soil resistivity and diameter of the rod from the drop-down list of each component.
3. The output simulated result will be shown in the grey cells.

Where:

1. The user needs to select the type of earthing methods from the drop-down list.
2. The user then needs to enter valid input value in the highlighted orange for each parameter.
3. The result can be obtained from the grey cells as shown below.

The results obtained in the template could also be printed from the Excel spreadsheet by clicking on File table followed by Print.

Step №4

Selection of Material & Size of Earthing Conductors

Where:

1. Subsections in red font inform user about the conductor type
2. The user then needs to select from the drop-down lists in each highlighted cell for each parameter as described in its adjacent cell.
3. The decision of the conductor size, type and material will be shown in grey cells.

Where:

1. User needs to select the types from drop-down lists
2. Results of minimum cross-sectional area of conductor will be shown

Template in MS Excel [.xlsx]

A systematic and easy-to-follow approach for the design activities of earthing systems for low-voltage installations was proposed. A comprehensive, economically viable, and technically acceptable template was developed using Microsoft Excel which can be useful for industry engineers when designing earthing systems that comply with national and international standards applied in Malaysia.

The use of this template was constantly verified throughout the development to execute accurate and precise results of design parameters in a time-saving manner.