okiebob
This is a excerpt from a article discussing Grounding Techniques for Low Voltage Systems, Contained within Article 250 of the NEC.
It may give you some food for thought on your grounding practices.
This electrical reference point can be related to the zero reference point in our numbering system.
We subconsciously delete the zero in our numbering system when counting, both up, in a positive direction, such as +1, +2, +3,.....etc and down, in a negative direction, such as -1, -2, -3,..... The zero is placed in the sequence as a place holder between the positive numbers and the negative numbers for the same purpose as the ground is placed in the electrical system. This reference point will establish the place holder between positive voltage levels and negative voltage levels exactly the same as the zero was placed in our numbering system. If a 120 volt alternating current system is used, that means the voltage will go from zero to positive 120 volts on a half cycle and zero to negative 120 volts on the other half cycle.
The reference point between the two is the zero reference or ground. If the ground is not at zero or is fluctuating above and below the zero reference point then the positive and negative voltage levels or differences will vary. If the reference point is 10 volts above ground level or the normal zero point, then the positive voltage will only amount to 110 volts with the negative voltage level being 130 volts.
Even DC systems require a stabilized voltage difference to some reference point so that voltage fluctuation does not occur. By tying the voltage system to a certain reference point, circuits and equipment can be assured of the proper levels of working voltage.
Even if an ungrounded system is established or the system is not tied to the ground reference point, there is still an assumed ground that will be naturally established through the distributed properties of the system components. Distributed capacitance is the natural capacitance of an electrical system that is present because
there are two different voltages in the system separated by some sort of insulator such as air or conductor insulation. Likewise, there exists a distributed inductance between the conductor in the system and any grounded surface. These natural properties of distributed capacitance and distributed inductance will provide a reference
point and a resulting difference of potential between any two different points in the electrical system. The only way that the two points will ever become the same or at the same potential is if there is a bonding conductor of some sort connected between the two points.
If a totally ungrounded system is suddenly grounded, the result will
be a discharge of that distributed capacitance resulting in an arc that will last until the two points are at the same potential or bonded and grounded together.
An unstable or fluctuating reference point in an ungrounded system can be caused by imbalances in resistance in a dc (direct current) system or imbalances in the impedance in an ac system.
This fluctuating reference point will cause the voltage levels in the system to vary which can cause some problems in electrical equipment.
Roger