Hero999 – “In the distribution transformer scenario, the earth simply acts as a return conductor for the current path. If one side of the transformer isn't connected to earth, then there will be no return current path, so no current will flow, as is the case with the isolation transformer, when the other side isn't earthed.”
That is absolute incorrect. If you had read my post #27 and post #30 you would know that the earth grounding of the neutral wire (that is the actual return conductor for the current path) is a safety feature and the earth isn’t relied on for carrying current.
The reason for this is simple, the earth’s resitivity is a variable that varies wildly from fairly low in some areas to near infinity in rocky areas. Power distribution has to be known and controlled and utilities can’t have one customer’s lights dim or flickering while the neighbor’s lights are very bright. Two wires are used and ground is only a safety connection.
This confusion is possibly caused by the misunderstanding of what the proper definition of ‘ground’ is. Here is a good description to help clear the confusion many have and is titled “An Introduction to Ground: Earth Ground, Common Ground, Analog Ground, and Digital Ground”.
https://www.allaboutcircuits.com/technical-articles/an-introduction-to-ground/ More specifically, in the case of power distribution being discussed, here is a document that describes a power distribution system and the ground connections used for safety.
http://www.samlexamerica.com/support/documents/13007-0612_GroundedElectricalPowerDistribution.pdf 1.0 CONDUCTORS FOR ELECTRICAL POWER DISTRIBUTION
For single-phase transmission of AC power or DC power, two conductors are required that will be carrying the current. These are called the “current-carrying” conductors. A third conductor is used for grounding to prevent the build up of voltages that may result in undue hazards to the connected equipment or persons. This is called the “non current-carrying” conductor (will carry current only under ground fault conditions).
2.0 GROUNDING TERMINOLOGY
In electronics, Ground is considered to be a common point, a point of zero potential and an infinite sink of electrons. In reality, most points we consider “grounded” are far from this perfect state. For purposes of electrical power transmission and distribution, the term “Grounded” indicates that one or more parts of the electrical system are connected to Earth, which is considered to have zero voltage or potential. In some areas, the term “earthing” is used instead of grounding. Connection to Earth may be made using Earth Electrodes like ground rods, buried wires, metallic pipes and other conductors in contact with the Earth.
Earth Ground is described in the context of lightning protection, safety and operational performance and is used for the following functions:
• Dissipate lightning strike energy in a manner that protects the surrounding area. Please see details under the Section 6 titled “Grounding System and Lightning / Ground Fault Protection”
• Provide a low impedance connection back to the AC power mains Ground or Neutral to reliably clear fault conditions by blowing a fuse or by tripping a circuit breaker. A “fault condition” occurs when a live, ungrounded current carrying conductor comes in contact with the exposed metal parts of electrical equipment
• Reduce the step potential gradient to safe levels
• Form a natural sink for atmospheric and radiated noise
• Provide an electrical antenna counterpoise.