Grounding Systems in Industrial Applications

Grounding systems are a vital part of every electrical design. With electricity comes the danger of electrocution, and as electrical engineering consultants, our job is to ensure safety around electricity, especially in the worst-case scenarios. Part of ensuring safety in electrical systems is proper grounding and bonding.

Purpose of Grounding Systems

The design of grounding systems has one primary function: minimizing the likelihood and harm of electric shock as well as preventing damage to property when a fault occurs. Electric current should safely follow a pathway of conductors to a load, and then return to the source without exposure to humans.

When a fault is introduced to the system (such as water, metal, fallen trees, failed insulation, etc.), it can cause electricity to follow the new path of least resistance. Fault conditions can cause dangerous situations for those interacting with, and near electrical equipment.

To prevent dangerous conditions, equipotentiality is established. This is an electrical engineering term meaning all exposed metal which normally shouldn't conduct electricity has to be bonded with a conductor and connected to the grounding system. Doing so ensures that in the case of a fault, all exposed metal rises to the same electric potential, and energy is dissipated to the ground.

The danger in electrical fault conditions is the difference in voltages. When the voltage is different between two points, and a person makes contact between those two points, high current will pass through the body and cause injury or serious harm. When the voltage is near identical at two points - such as when a bird sits on a bird sits on a high voltage wire - low current will pass between those points, causing no harm.

An electrical system with a ground must have a low impedance path to ground. A conducting cable that is sufficiently rated for fault conditions is connected to a ground rod, plate, or grounding grid. This is the definition of a ground. For equipment to be grounded, the ground must be bonded to non-energized equipment to ensure that no dangerous voltages are introduced between grounding conductors and neighbouring electrically conductive surfaces. Additionally, dangerous voltages must be prevented between the ground conductor and the nearby earth itself.

Grounding System Design

The design of a grounding system starts with how much power you have. As everyone knows, with great power comes great responsibility. In electrical engineering, the same applies to grounding systems. With greater power (and voltage), grounding systems must be designed to safely dissipate larger amounts of power in the case of a fault condition.

Differences in grounding designs is largely based on the operating voltage and short circuit fault condition of the circuit. With higher voltages and short circuit current, the more robust grounding systems must be to ensure equipotentiality.

With low-voltage systems, such as a residential home, a ground rod or plate (literally a metal plate or rod buried in the earth) is used to establish a connection to the earth. This lets us essentially use the earth as a massive resistor sink to ground a circuit. To do so, the ground is connected to the neutral in the circuit, which is used as a return path for electricity under normal use. This allows us to establish equipotentiality on the bonding conductor and have a low-impedance path to the ground for the power to dissipate.

High Voltage Systems

High voltage systems, typically seen in industrial applications, add significant complexity to the grounding design. These systems are defined in the Canadian Electrical Code as anything above 1000V. With high voltage, a difference in voltage enough to cause harm can easily occur during a fault condition. This means that establishing equipotentiality even over small distances is important, and the focus of high-voltage grounding systems is to ensure the safety of operators during faults.

High-voltage systems can be seen commonly in industrial manufacturing, mining facilities, and substations. High-voltage systems are generally used when a massive amount of electrical power is being used in the facility. This typically means the short-circuit current is larger, due to the amount power being supplied.

Grounding for High-Voltage, Industrial Applications

Instead of using a single plate or rod, high voltage systems use a grid of bare conductors placed in the ground under a facility. The voltage and possible short circuit amperage both play a part in how this grid is constructed. In lower-power cases, the grid can be simplified to a perimeter around the facility. To ensure proper grounding, the ground grid or grounding perimeter is tied to ground rods or plates.

Step and Touch Voltage

Two values are used to ensure the safety of grounding systems: step voltage and touch voltage. At these high voltages, the potential voltage difference between steps on the ground can be significant enough to cause a deadly current to pass through the body - that difference between steps is called step voltage. Additionally, touching a bonded piece of equipment will introduce a difference of voltage between the person touching it and the voltage of the ground grid underneath them - that difference is called touch voltage.

Both values are used to determine the details of the ground grid; this includes bare conductor size, size of the grid, and how compact the grid must be. Grounding systems are designed to have step and touch voltages that are safe for a human to experience. Of course, the design of grounding systems is more complicated than can be explained within this article. Many factors are considered; the moisture content of the earth beneath a facility, the potential for lighting strikes, the facility's equipment, the electrical distribution design, and more.

There are other practical reasons for proper grounding design in industrial applications. One example is keeping "noise" to a minimum on control systems, where low-voltage signals can get disrupted by variations in the power supply introduced by other electrical equipment, or simply preventing static buildup. This is important in any facility where control systems are used, to prevent machinery not operating as intended or breaking down. But most importantly of all, grounding systems are crucial for industrial power to keep everyone safe when an unpredictable electrical fault occurs.

Do you have an industrial project in the works? Please reach out to see how we can help.

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