The Third installment of the series “The Power of Zap” is called Grounding 101. Jim Daggon, Rice Lake senior product engineer and Chuck Crowley senior technical support manager focus on the importance of proper grounding for safety and the performance of sensitive electronic devices. The idea of grounding is that the earth itself acts as the electrical ground, providing not only a common reference for all electrical devices, but also a standard between devices regardless of location. The earth is used as the common reference conductor.
The consideration that the earth acts as a constant conductor is the underlying principle, and in the larger sense, it does. However, the connection to the ground or “earthing” needs to have the lowest resistance possible. Any resistance due to improper or faulty connections will allow the presence of a current to flow. In the context of safety, current flowing through a vital organ is what causes injury or death. The frequency of the alternating current, the duration of contact, and the path of contact are all important factors in determining the severity of the shock. The connection to the earth consists of two basic parts: the grounding electrode and the connection (or bonding) to that electrode. Any resistance introduced in the grounding path could lead to a damaging or dangerous condition.
The relationship between resistance, current, and voltage is revealed in Ohm’s Law1:
I = V / R
I = current flow
V = voltage
R = resistance2
Using this equation, if the resistance is 0, then the current flow will be maximized in the ground circuit. (This is what you want, not current flow in another path that does not include the ground, but may include YOU!) The accepted National Electrical Code (NEC), standard for a grounding circuit is 25 ohms or less, but much lower values can be obtained using multiple grounding electrodes. Click here to read the entire part 3 article.