Last Updated on January 20, 2023 by Josh Mahan
When working with high-powered electrical equipment and appliances, it’s essential to ensure that they are appropriately set up and wired to avoid potential safety hazards and other complications that could damage said equipment or nearby individuals. Electrical grounding systems are a commonly used tool specifically designed to protect against the dangers of sudden, high-voltage discharges by removing excess current flow. Grounding is essential in many industries that involve powerful electrical equipment.
Data centers, in particular, utilize a massive array of highly powerful technological tools and machines that require considerable amounts of power to function correctly. Because of this, data centers need to ensure that they’re effectively utilizing electrical grounding systems to protect the lives of their employees, as well as their machines. Please continue to find out everything you should know about the different techniques and types of electrical grounding systems.
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What is Electrical Grounding?
Put simply, “grounding” refers to a low-resistance path that’s been constructed to carry an electrical flow into the ground, and a “grounded” connection refers to a connection between electrical equipment and the ground through a wire. When wired correctly, appliances and devices are given a secure place to safely discharge excess electrical currents without creating damage or safety hazards to equipment or nearby people. According to The National Electrical Code (NEC), “ground” is defined as a type of conduction connection- whether accidental or intentional- between equipment or an electrical circuit and the earth or some conducting body used in place of the earth.
The purpose of the NEC is to help limit the voltage potential from line surges, lightning, and contact between other lines of higher voltage through the use of equipment earthing conductors. This tactic inherently makes the entire electrical system safer and provides protection against significant fluctuations in the power supply. If you want to help ensure the safety of your data center equipment and staff, you must utilize a perfectly grounded and secure network. Otherwise, you risk significant damage to your equipment, as well as people’s lives.
The NEC offers a list of detailed requirements regarding the setup and functioning of grounded systems. Summaries of other essential requirements can be found here at the OSHAcademy Occupational Safety and Health Training website.
Why are Electrical Grounding Systems Needed?
As stated above, grounded electrical systems are essential for operating a safe and secure data center. However, they are also necessary for large-scale residential and commercial projects. While installing and maintaining grounding systems are complicated and time-consuming process, it is essential to prevent dangerous situations that could lead to issues if an appliance’s internal wiring were to short circuit. There are several risks of utilizing ungrounded electrical systems, such as fire and electrical shocks, which may lead to fatal accidents. Some of the significant advantages of using a properly grounded system include:
Excess power can surge for many reasons within an electrical workplace, producing massive voltages of electricity in systems and causing fires and shocks that can injure, if not outright kill, humans. Grounded systems offer overload protection by forcing that excess of surged energy into the earth, protecting people and electrical appliances, along with the critical data they may contain.
Protection Against Electrical Hazards
In a worst-case scenario, ungrounded systems can lead to shocks and fires that damage and destroy equipment, resulting in significant data loss as well as injury and death of nearby individuals. Grounded systems eliminate these electrical hazards and protect the equipment from sudden voltage surges, preventing electrical fires and reducing the chances of equipment damage.
Grounded systems are designed to ensure that circuits aren’t easily overloaded and distribute the correct amount of power between specific data sources. This ground provides a common point of reference for critical voltage stabilization.
What are The Three Types of Grounding Systems?
In general, there are three types of grounding systems that are important for people to understand, along with their various advantages and disadvantages. These three systems include:
- Ungrounded Systems
- Resistance Grounded Systems
- Solidly Grounded Systems
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This section may be confusing for some readers since we just went through several paragraphs detailing the importance of not having ungrounded electrical systems. While that’s true, and ungrounded systems are inherently riskier, they do exist and do serve specific purposes, though they were much more common back in the ’40s and ’50s. As such, we need to take the time to explain how they operate and the various advantages and disadvantages they provide.
The first thing to understand about ungrounded systems is that they’re not actually ungrounded. Electrically speaking, your system is connected to the ground through the capacitance between the lines and the earth. Meaning it’s more correct to call it a capacitance-grounded system. It’s simply referred to as an ungrounded system because of convention and because there isn’t an intended physical connection between the involved powerlines and the ground.
Put simply, in an ungrounded system, the ground-fault current is negligible and can be utilized to reduce the risk of shock to people. When a fault occurs, two wires are needed to carry some of the currents to avoid excess voltage that will cause excessive heat and damage the equipment involved. Because ground fault is negligible, finding faults can be very difficult and time-consuming, making the cost of ungrounded systems extremely high.
Advantages of Ungrounded Systems
There are a few specific advantages that come with utilizing an ungrounded system. Some of the most critical benefits of ungrounded systems are that;
- You have a negligible ground-fault current.
- They offer a relatively low value of current flow for lint-to-line ground faults.
- There is a low probability of line-to-ground acting faults escalating to a phase-to-phase or 3-phase fault.
- They assure a continuous operation of processes on the first occurrence of a lint-to-ground fault.
- They present no flash hazards to personnel in the event of an accidental line-to-ground fault.
- They minimize shock risks to people.
Disadvantages of Ungrounded Systems
Some of the inherent disadvantages of ungrounded systems are;
- They use two wires to carry an amount of current intended for three wires in the case of a fault, increasing heat and the potential for damaging equipment and insolation.
- They make it relatively difficult and time-consuming to locate any faults.
- All lines need to be individually tested.
- They carry very high operational and maintenance costs.
- They don’t control for transient overvoltages.
- A second ground fault on another phase will trigger a phase-to-phase short circuit of the system.
While they do carry some notable advantages, the disadvantages are far more prominent for ungrounded systems, which is why relatively few are utilized today compared to several decades ago.
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Resistance Grounded Systems
Resistance grounding, in short, is when electrical power systems have connections between a neutral line and the ground through a resistor. Said resistor is used to limit the fault current through the natural line. If your voltage doesn’t change, your electrical current will depend on the size of the resistor involved, according to Ohm’s law (V=IR).
There are two distinct types of resistance grounding systems; high resistance grounding and low resistance grounding.
High Resistance Grounding
High resistance grounding (HRG) systems actively limit ground fault currents to <10 amps and are commonly used in mills and plants wherever an ongoing operation of processes is intervening with the event of a particular fault.
Low Resistance Grounding
Low resistance grounding (LRG) systems actively limit ground-fault current to between 100-1000 amps. These systems are typically utilized in medium voltage systems of 15kV or less and are designed to trip protective devices once a fault occurs.
Advantages of Resistance Grounding
Resistance-grounded systems (both high and low) carry several advantages, especially when compared to ungrounded systems. For example, because the current in the neutral for these systems is controlled instead of negligible, potential system overvoltages are controlled for. Reduced current equates to reduced heat, which minimizes the overall wear and tear of the electrical system as a whole, which is especially important for keeping essential equipment safe and functioning in data centers. Some additional advantages of these systems also include the fact that;
- Reduced currents also reduce the risk of shock and blast/arc flash.
- The systems limit the ground-fault current to a low level.
- They control transient overvoltages.
- They reduce electrical shock hazards.
- They maintain continuity of service.
- They reduce mechanical stresses in equipment and their circuits.
- They reduce the line voltage drops caused by the cleaning and occurrence of a ground fault.
Disadvantages of Resistance Grounding
Some of the primary disadvantages of resistance grounding systems are;
- High frequencies can appear as a type of nuisance alarm.
- A ground fault may be left on the system for an extended period.
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Solidly Grounded Systems
Solid grounding refers to a grounding system in which an electrical power system is directly connected to the ground, and there is no intentional independence included in the circuit. Solidly grounded systems can utilize large amounts of ground-fault current and thus make faults much easier to locate compared to ungrounded systems. These systems are most commonly used in industrial or commercial power systems, and backup generators are typically kept on standby if a fault shuts down particular production methods.
Much like resistance grounding, solid grounding can significantly reduce the potential for overvoltages within an electrical system. However, these systems can have massive amounts of ground-fault current. Because of this, solidly grounded systems cannot operate with a ground fault- since all of the currents in the system run from fault to ground.
Advantages of Solidly Grounded Systems
Some of the primary advantages of solidly grounded systems include;
- They provide reasonable control over transient overvoltage from neutral to ground.
- They allow users to locate faults quickly and easily.
- They can supply line-neutral loads.
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Disadvantages of Solidly Grounded Systems
Solidly grounded systems feature several distinct disadvantages that vastly outnumber the advantages they bring to the table. For example;
- Solidly grounded systems possess a severe arc flash hazard.
- They can create problems in the primary system.
- They require the purchase, installation, and maintenance of an expensive and complex main breaker.
- They provide high values of fault current.
- They have the potential to cause unplanned interruptions in production processes.
- They can potentially cause severe equipment damage in the event of a fault.
Final Thoughts and Considerations
Now that you have an adequate understanding of the different types of electrical grounding systems and their various advantages and disadvantages, you should have the ability to select the most optimal type of grounding system to protect the equipment used in your data center. If you’d like to learn even more about essential data center management, power, infrastructure, cleaning, and more, please consider contacting us at C&C Technology Group today to learn about our wide array of expert services. And don’t forget to also explore our wide selection of quality educational articles.