All about Electrical Grounding Systems!

In this blog we will cover the Need of electrical grounding system, its importance, types of grounded system, common methods and the factors that effects the grounded system installation, safety tips etc. Simply, this blog is all about Electrical Grounding System.

The ground is the common point of return for an electrical flow. The grounding system is a backup pathway that has an alternate route for an electrical current to flow to ground due to any risk in the electrical system before it gets a fire or shock.

What is Electrical Grounding?

Simply, "grounding" means a low-resistance path has been made for electricity to flow into the ground. A "grounded" connection includes a connection between the electrical equipment and a ground through a wire. Once wired properly, this provides your devices and appliances a secure place to discharge excess electrical current. This will potentially prevent electrical equipment from several risks. The ground wire in an electric outlet is basically a safety valve.

The National Electrical Code defines ground as a "conducting connection, whether intentional or accidental between an electrical circuit or equipment and earth or some conducting body that serves in place of the earth." The NEC also states that "the earth shall not be used as the sole equipment-grounding conductor." The (NEC) limits voltage from lightning, line surges and contact with a line of higher voltage by using equipment earthling conductors.

The purpose of grounding an electrical system is to make an entire system safer and provide protection against the fluctuations in power supply. The system should be perfectly grounded, if you want to have a safe and secure network and to avoid risks of human lives.

Why do we need to Ground the Electrical System?

Particularly in large-scale residential or commercial projects, some people think that it will be difficult and time consuming to install a grounding system and any additional construction of electrical material, if timely maintenance is performed. This is an extremely dangerous practice that could lead to a shock if the internal wiring in the appliance become a short circuit.

According to John Grizzy Grzywacz, Professor Emeritus of the OSHA National Training Institute, "Most utility accidents and fatalities with respect to line contact are a result of lack of appropriate PPE, lack of insulated line cover up, or lack of appropriate grounding."

Common risks of an ungrounded electrical system are electrical shocks and fire as electrical current always follows through the low resistance path. Workers at workplace are at a higher risk when an ungrounded device discharges excess electricity. As a result, electricity will transfer to the person causing injury or that leads to death. The chance of a fault in an ungrounded system is very high. In order to get best protection of an individual and an electrical equipment, make sure that your system is grounded.

Generally, Power Systems are connected to ground through the capacitance between the lines and the earth and there isn't a direct physical connection between any of power lines and the ground.

Types of Grounded System:

Three different types of grounding systems that are important are listed below.

• Ungrounded Systems
• Resistance Grounded Systems
• Solidly Grounded Systems

When an electrical power system operates and there is no intentional connection to ground then called as ungrounded system. Though these systems were normal within the '40s and '50s, they're still in use nowadays.

In an ungrounded system, ground fault current is negligible therefore can be used to reduce shock risk to people. Once a fault occur, two wires needs to carry an amount of current that was assigned for three wires: the rise in current and voltage will jack up the heat and lead to unnecessary damage to an electrical system.

As ground fault current is negligible so finding any fault become very difficult and time consuming process. The opportunity cost of a fault in an ungrounded system is extremely high.

Resistance Grounding is when an electrical power system has a connection between neutral line and the ground through resistor. Here, resistor is used to limit the fault current through a neutral line.

There are two types of resistance grounding: high resistance grounding and low resistance grounding.

On the other hand, Low-resistance grounding (LRG) systems are used in medium voltage systems of 15kV or less and tripping protective devices once there's a fault.

Solid Grounding means an electrical power system is directly connected to the ground and there is no intentional added impedance in the circuit. These systems have the potential to own large amounts of ground-fault current, thus faults are easily located.

It is commonly used in industrial and commercial power systems. There are backup generators in case when a fault shuts down a production method.

Common Methods for Electrical Grounding Systems:  

Grounding plates are made up of copper or Galvanized Iron (GI) and placed vertically into the ground in a pit (filled with charcoal and salt layers) over 10 feet deep. For a higher electrical grounding system, the earth moisture condition must be maintained around the grounding plate system.

The National Electric Code requires that ground plates have at least 2 ft of surface area exposed to the surrounding soil. Ferrous materials must be at least .20 inches thick, while non-ferrous materials (copper) need only be .060 inches thick.

A galvanized steel pipe (mixture of salt and charcoal) is placed vertically into the soil through drilling for connecting the grounding wires. The length and diameter of the pipe size mainly depends on the type of soil and electrical installation (magnitude of current). The soil moisture will decide the pipe's length to be placed in the ground.

A copper rod with galvanized steel pipe is placed upright into the ground. This is very similar to pipe grounding. Here, rods are in the form of electrodes therefore decreasing the resistance of earth to a specific value. The National Electric Code (NEC) requires that driven rods be a minimum of 8 feet in length and that 8 feet of length must be in direct contact with the soil.

 

image source: https://www.ppindustries.com.au/

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  About The Author

  Abdur Rehman is a professional electrical engineer with more than eight years of experience working with equipment from 208V to 115kV in both the Utility and Industrial & Commercial space. He has a particular focus on Power Systems Protection & Engineering Studies.