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Ground, Earth vs Neutral

These three mentioned have essential use in the field of electricity.

This article will identify the difference between them by knowing their specific purposes. For easy identification, normally ground wires are in green/yellow color while neutral wire in blue/white color. It may vary based on the country or standard you’re working with and you should be aware of.

Neatral and Ground Busbars

Ground and Earth

Ground and Earth are the same in puprose, it’s just happened that the term Ground has been used by US while Earth by UK. Going back to its purpose, ground or earth is part of the Electrical Protection System where anything bonded to it is safe to touch as long as it’s sized, installed and maintained with regards to the standard.

Grounding or earthing are usually buried under the ground in specific connections accessed through pits and enters a property or equipments.

It’s clear that ground or earth is used for safety purposes against leakage or residual current that is flowing to the least resistance path. This leakage current is lesser than the load current usually in mA but enough to kill someone if not bonded properly.

Healthy ground must be maintained and measured regularly to ensure safety. Most commonly used measurement tool for ground value is the Ground Resistance Tester. The NFPA and IEEE recommend a ground resistance value of 5 ohms or less while the NEC has stated to “Make sure that system impedance to ground is less than 5 ohms specified in NEC 50.56. In facilities with sensitive equipment it should be 5 ohms or less.

Ground rods must be observed and cleaned too. It’s prone to rust as it is installed in pits. Observe cable from equipment to rods to as its laid outside and prone to rust and damaged. Equipment grounding and panel ground bonding terminals must be tight and checked regularly. Make sure it’s not rusty and no any physical damages.

Checking of Ground Rods for Grounding Resistance Test

Neutral

Neutral is designed as a part of power system as load carrying conductor. It’s designed to carry the return path of AC current in a circuit back to source.

Neutral Busbar inside the panel

Neutral wire is different from ground or earth wire as neutral wire are assumed to be charged when loaded. However, this neutral wire is connected to ground to create another terminal of neutral wire with zero potential.

Neutral wires are bonded to each panels and must be checked regularly. Usually, it has common terminals and tightness must be checked as well.

Therefore, the main difference of Ground/Earth and Neutral is that the Ground/Earth was designed for safety purposes while the Neutral was design to carry load current as a return path to the source.

Earthing Networks

  • Role: making fault currents and external source currents (lightning) pass through the ground
  • Concept:
    • Mesh system (metal structure)
    • Short and broad connexions (to prevent oscillations)
    • Large enough section to let a fault through
    • Buried to lower Z and to prevent oscillations
    • Interconnected earth systems to lower their impedance
    • Solder the connections for better stability

All points of the Earthing System must be at the same potential

No differences of potential between two machines whatever the earth resistance (depending on the resistivity of the ground) is

All Earth points must be interconnected

If the two earthing systems are not connected to each other, a voltage drop may appear, as well as circulating currents that include the earth in their loop.

Example : a sensor and the device to which it should be connected when they are connected to non equipotential earth systems.

Standard Earthing

  • A mesh system buried 60 to 80 cm into the ground is used
  • All earth electrodes must be connected to it
  • Connection points must be decided before building
  • Connecting wires are pulled out of the ground

Earthing cables of metallic equipment such as motors, transformers, boards, builds,etc are connected to that meshed network.

Connection to the Mesh System

In the building industry, the places where earthing cables leave the ground are chosen before the building starts.

Earth a motor rack

Earthing a transformer

Transformer Grounding

The transformer enclosure is electrically insulated from the ground by wheels, and the connection to the earth is made thanks to earthing cables. The fault current will be forced through those cables, which then allows the insertion of a TI to control the fault current value.

Earth wire connection

The scheme shows a standard earthing to a metallic piece: a flat piece of plain or galvanised steel is soldered for that purpose. The terminal of the earthing cable is then screwed into it.

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