Engineering and Consulting Services

Grounding Systems

Basic principle #1 +
     Current follows the path of least resistance.
Basic principle #2 =
     Current will exist in undesirable forms.
The need to ground.

The purpose of grounding is to control where this undesirable current goes. Undesirable current includes lightning discharge, power system neutral return, ground fault currents, and noise currents. The earth is an obvious natural electrical conductor because of its sheer size and accessibility. The connection to the earth can be achieved with bare metallic conductors, copper plates, steel pipes, and ground rods.

Ideally, we would like to have zero resistance at any point in the grounding system. Unfortunately, this not possible, so our goal is to minimize the resistance to earth at all points in the system. The total resistance in the system will vary with the grounding conductor size, type and size of electrical connectors, contact resistance between the conductors and the soil, the resistivity of the soil, the area of the grounding system, the temperature, and more. We ground for three reasons: personnel safety, equipment protection, and electrical noise reduction. Personnel safety should be the top priority of a grounding system and is best achieved by equalizing the potentials of all conductive objects that are within reach. Another safety objective is to provide a low impedance path back to the power source in the event of an electrical fault to ground.

Equipment protection involves providing an alternate path for lightning and faults to avoid damaging equipment. Electrical noise reduction is accomplished by ensuring that the impedance to earth or the ground impedance between interfacing equipment is kept to a minimum value.