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When does the earth circuit comes to play? Why is it that you can disconnect the earthing lead and still have a functioning electrical system?

Hi Ankomah,

Thank you for your question regarding the purpose of the earthing portion of the grounding system in a proper functioning electrical system, it is our pleasure to help.

In a properly designed electrical system, the Over Current Protection Devices (OCPD) such as fuses and circuit breakers will indeed continue to function even without a connection to earth.  In other words, if you have a good electrical system, you can remove the connection to the ground rod and the power will still flow and the circuit breakers will still trip in the case of a fault.  This is all true, but that is not the purpose or function of the earthing system, now is it?

Imagine the space shuttle up in orbit.  It has lots of electrical systems and no earthing system at all.  If we were able to look at the wiring systems inside the space shuttle, we would see that they not only have the traditional 3rd green wire ground, but they additionally have an equipotential grounding and shielding system.  The difference in potential from any metallic object to the next within the shuttle would be very low.  The reason for this extra grounding system is because the shuttle has no mechanism to remove induced currents, transient energy, absorbed radiation, etc.  So the chassis of the shuttle itself becomes the ground source, slowly absorbing energy, in essence becoming a giant capacitor.

Lets say we were able to measure the voltage of the shuttles chassis when it first went into orbit, against some other remote ground reference.  Let’s say it was Zero (0) volts.  What do you think the voltage would be after a few days in orbit?  What do you think the chassis’ voltage would read after a few weeks in orbit?  You might be surprised as it could be many thousands of volts!

So what about the regular hot wires?  Again, if we measured the single-phase hot wire on the shuttle when it first took off against some remote ground source, we would see 120 volts.  But after a few weeks in orbit, if we were to re-measure that same hot wire against a remote ground source, we would see thousands of volts!  In other words, in our shuttle example, if the chassis measured 1,000-volts after a few weeks in orbit, the hot wire would measure 1,120-volts.  From our perspective on earth, it would look like the shuttles voltage system is all out of whack.  But on the shuttle, every volt meter would read just fine and would only show a normal 120-volt system.
We see this capacitive phenomenon every day with helicopters.  They fly around charging themselves to the point that when they land, the choppers arc and spark when they touch down as they discharge the built up energy.  But on the helicopter, they are not aware of the change in voltage.  The same is true for ships at sea.  They discharge into the surrounding ocean, but not as effectively as they need.  After a few years of holding a charge, the ship itself must be demagnetized.  Pearl Harbor in Hawaii is famous for having a buried degaussing system right in the harbor.  Ships like to pull in to port for no reason other than to make use of this system.

The purpose for your earthing system at your home or business, has nothing to do with proper circuit operation, or even for the purpose of providing fault current protection.  The purpose of the grounding system is to provide a reference point so that our electrical systems don’t charge our buildings like a helicopter or the space shuttle.  The earth connection of course has many other purposes as well.  Not only does it remove the unwanted stray currents that form on conduit and other metal objects, but it is vital for removing electrical energies from sources outside of the supplied power, such as lighting strikes.

If you were to remove the earth connection from your electrical system, you will start to find errors of all kinds.  Your conduit and metal objects will start to get warm to the touch.  Harmonics, transients, objectionable currents, and electrical noise of all kinds will interfere with your systems.  GFCI circuit protection may trip and fail for unknown reasons and would certainly be less reliable.  Your electric bill may increase as more and more power is pumped into the ever increasing impedance of your electrical system.

 

Additional issues such as insulation degradation due to voltage potential rises relative to ground will begin to occur resulting in fire hazards.  Electronic equipment of all kinds require a solid earth connection as a reference point for their internal workings of the electronic systems.  Surge protection systems require an earth connection to work properly.  Where else will they place the unwanted energy from a surge is not to the earth?  Back on the neutral wire?  What if the surge came from the neutral?  Where would the surge protector place the energy then?  On the hot wire?

The last point that you should consider, is that every single electrical standard has been increasing its requirements for grounding and earthing systems year after year.  These standards have been written by very smart people and there are many reasons for the increased requirements.  It would take a long time to get into all of them, but the reality is that electrical system that have excellent earthing systems, function better than those that don’t.

We hope this answers your question.  Please feel free to contact us again in the future should you have any further inquiries.

 

Best regards,

The Engineering Team at E&S Grounding Solutions

 

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