Earth Grounding Basics
When it comes to electrical wiring, earth grounding is an important safety consideration. Grounding an electrical system serves as a low-resistance path for a fault current and helps minimize the potential for electric shock. Review the basics of earth grounding to better understand its importance and applications.
What is Earth Grounding?
Earth grounding is the process of placing a ground electrode from a circuit conductor directly into the earth. This is different from equipment grounding, which involves grounding operating equipment such as an electronic device. The purpose of earth grounding is to provide a means of dissipation for power surges caused by lightning strikes, static charges and other types of electrical interference. The most common way to create a proper ground is to attach a neutral wire or cable to a rod, pipe or plate and bury it in the ground.
Proper Earth Grounding Values
The resistance value of the ground wire is important when it comes to creating a safe electrical system. In an ideal setting, the ground wire delivers a resistance of zero ohms. However, economic and physical reasons often make such an ideal resistance impossible. As such, there are different standards for acceptable resistance depending on the specific application. For example, the telecommunications industry recommends an earth ground that offers a resistance of five ohms or less. According to the NEC, the maximum resistance that should be accepted for any application is 25 ohms.
Types of Earth Grounding Systems
Different applications may call for different earth grounding systems. In general, there are two different systems used for grounding cable – simple and complex. Simple grounding systems are the most common type of system, and include the use of a single ground electrode. This type of system is used almost universally for homes and single-building electricity applications. Complex systems, on the other hand, require the connection of several ground rods. Placed in a mesh or grid pattern, the additional grounding provided by these systems is ideal in high-electricity applications such as power plants and central power offices.
When determining how many earth grounding rods a particular location may need, resistance of ground soil, total level of electrical current and other factors need to be taken into account.