The Ground Dilemma

Engineering takes its terms from the English language.  Usage then takes over, and a word can take on many different uses.  There is no way to control and regulate the way words are used.  One of these words is “ground”.  Here are a few example of how we use this word in daily speech:

Ground floor

Ground ball

Ground round

Ground cover

Ground crew

Coffee grounds

Grounds for divorce

Playgrounds

Then engineers come along and there are dozens of new uses.  For example:

Ground wire

Ground plane

Reference ground

Signal ground

Power ground

Digital ground

In power engineering, the word “ground” means one thing: an earth connection.  In power engineering all uses of the word are controlled by the National Electrical Code, which has the power of law.  The NEC is the basis for municipal codes that control how buildings are wired,and this involves our safety in many ways.  Examples of usage of the word in power engineering are:

Ground conductor.  That conductor that carries power current and is connected to earth at the service entrance

Grounding conductor.  That one conductor that connects the ground conductor to earth at the service entrance.

Ungrounded conductor.  The power conductor that carries a voltage.

Equipment ground.  All metal surfaces that could come in contact with an ungrounded power conductor.  This includes motor cases, receptacles, conduit, trays, etc.

Equipment grounding conductor.  A conductor that connects all equipment grounds together.  It can be a green wire or a bare wire.  It is also called a safety wire.

Grounds are sometimes thought of as “sinks” for electrical noise.  This is not a valid way to look at grounds.  A better definition is this:  A ground is a conductor that can be used to control electromagnetic fields.  If used correctly it can control the path taken by signals or power.  If used correctly it can limit radiation and reduce susceptibility.  If used correctly it can provide power safety or protection against lighting. 

A grounding wire to earth is not needed, except to meet the requirements of the NEC.  Remember that airplanes have sophisticated electrical systems and they do not carry a grounding wire.  People do not get shocks in airplanes and they are not affected by lightning.  And yet engineers call the framework of an aircraft “ground.” And if the airplane can’t fly, it is grounded. 

When we colonize the moon will electrical connections to the moon be called mooning?  Just thought I would ask.