Earthing Strip Size Calculator

How to Use Earthing Strip Size Calculator

Determining the correct parameters of protective grounding and earthing strips ensures safety against sudden electrical shock risks and transient short-circuit failures. Follow these professional steps to compute compliant earthing strip sizes:

1. 1
   Determine short-circuit fault current: Retrieve the prospective ground fault current (I) in kiloamperes (kA) from utility substation coordination parameters or system load flow studies.
2. 2
   Enter fault duration: Input the clearing speed or duration of the protective device (fuses, circuit breakers, or overcurrent protective relays) in seconds.
3. 3
   Select earthing strip material: Select the composition of your earth conductor strip. Standard industrial choices include GI Strip (Galvanized Iron), Copper Strip, or Mild Steel Strip.
4. 4
   Enter strip thickness: Define the desired thickness of your earthing strip in millimeters (mm). Standard sizes are typically 3 mm, 4 mm, or 6 mm depending on mechanical conditions.
5. 5
   Run the calculation: Click the "Calculate Sizing" button to instantly review the minimum cross-sectional area, recommended standard commercial strip width, and design assessment.

In standard commercial layout and building projects, selecting a robust strip ensures that galvanic soil corrosion does not degrade the protective circuit pathway over decades of active operations.

How to Calculate Earthing Strip Size

Protective grounding systems rely on massive flat strips to safely discharge intense fault currents into ground layers without melting or suffering severe structural degradation. Designers utilize standard thermodynamic equations to size the minimum conductor profile.

The Adiabatic Sizing Equation

Sizing grounding strips is governed by the standard thermodynamic adiabatic formula defined in international codes including IEC 60364-5-54 and BS 7671:

Where:

• A = Required minimum cross-sectional area of the earthing strip in square millimeters (mm²)
• I = Prospective short-circuit ground fault current in Amperes (A)
• t = Clearing speed of the protective safety relay or circuit breaker in seconds (s)
• K = Material thermodynamic constant representing thermal limits (Copper = 226, GI = 80, Mild Steel = 78)

Recommended Standard Width Sizing

Theoretical calculations yield continuous decimal areas. To select physical products, engineers compute the required width and round upward to the next manufactured size:

The width value is then rounded up to the nearest practical manufactured standard width from the following industrial sizing options: 20 mm, 25 mm, 30 mm, 40 mm, 50 mm, 65 mm, 75 mm, or 100 mm.

Real-World Engineering Example

Let's verify these steps with a standardized design scenario for a commercial processing factory:

• Prospective short-circuit fault current (I) = 25 kA (25,000 A)
• Fault clearing duration (t) = 1.0 second
• Grounding material = GI Strip (Galvanized Iron) (giving K = 80)
• Prospective strip thickness = 4 mm

Step 1: Compute the required cross-sectional area (A)

Step 2: Calculate the theoretical strip width

Step 3: Select standard commercial width
We compare 78.13 mm with standard widths (20, 25, 30, 40, 50, 65, 75, 100 mm). The next larger manufactured standard width is 100 mm.

Conclusion: Sizing a Galvanized Iron (GI) earthing strip to carry 25 kA for 1.0 second with 4 mm thickness requires a theoretical area of 312.50 mm². Sizing engineers select a standard 100 mm × 4 mm GI Strip (Total Area = 400 mm²). This selection provides a comfortable safety overhead and ensures that long-term soil corrosion will not compromise system integrity, complying with IEC 60364-5-54 and BS 7671 standards.

Earthing Strip Size Calculator Chart

This reference sizing chart outlines standard protective grounding and earthing strip sizes across common engineering configurations.Sizing parameters utilize a standard fault clearing duration of 1.0 second under baseline IEC 60364 guidelines.

Note: Calculated sizes represent minimum thermodynamic cross-sections. In highly aggressive, salty, or acidic soils, sizing engineers recommend incorporating thicker sacrificial margins or utilizing contextual internal links to evaluate comprehensive grounding grids.

Copper vs. Aluminum Conductor Sizing for Earthing Strip Size

Choosing the correct conductor material directly affects sizing, weight, and installation cost. Copper has a higher electrical conductivity, while Aluminum is lighter and less expensive. However, aluminum has only 61% of copper's conductivity, requiring larger physical sizes:

Aluminum is widely used for major service feeders, while copper is the standard for branch circuits in Earthing Strip Size systems due to terminal connection reliability.

Short-Circuit Thermal Capacity of Earthing Strip Size Conductors

Under short-circuit conditions, cables experience high currents for a fraction of a second. The conductor must have sufficient thermal mass to absorb this fault energy without letting its insulation melt (160°C for PVC, 250°C for XLPE). The minimum cross-sectional area required is calculated as:

Where t is the breaker trip time in seconds and k is a material constant (115 for copper with PVC). If the ground fault currents in your Earthing Strip Size setup are high, you may need to increase the cable or ground wire sizing to handle short-circuit stresses.

IEC vs. NEC vs. BS Standards for Earthing Strip Size Sizing

Conductor sizing for Earthing Strip Size must comply with specific local standards depending on geographic jurisdiction. The table below compares the primary standards used worldwide:

Choosing the correct standard ensures legal compliance, proper ampacity margins, and safety from electrical thermal hazards during continuous operation of Earthing Strip Size.

Earthing Strip Size Calculator Frequently Asked Questions