Grounding is so much more important than most people think!
Grounding errors can cause electrical shock, fires, equipment damage, and power quality problems.
In this article, we’ll give you a basic understanding of grounding and outline its importance.
What is a ground?
The US National Electrical Code (NEC) Article 100 defines a ground as: “a conducting connection, whether intentional or accidental, between an electrical circuit or equipment and the earth, or to some conducting body that serves in place of the earth”.
Grounding actually encompasses two different subjects: earth grounding and equipment grounding.
Earth grounding is an intentional connection from a circuit conductor, usually the neutral, to a ground electrode placed in the earth. Equipment grounding ensures that operating equipment within a structure is grounded properly.
These two grounding systems must be kept separate except for connections between the two systems. This prevents differences in voltage potential from a possible flashover from lightning strikes.
The purpose of a ground is to provide a safe path for the dissipation of fault currents, lightning strikes, static discharges, and electromagnetic interference (EMI).
What affects the grounding resistance?
When installing grounding systems, focus on ways to reduce the ground resistance. Here are ways to effectively lower ground resistance:
1. Driving ground electrodes deeper
The resistance level can generally be reduced by an additional 40% by doubling the length of the ground electrode.
2. Multiple ground electrodes
More than one electrode is driven into the ground and connected in parallel to lower the resistance.
3. Increased diameter of the ground electrode
Although this may have very little effect, it does help lower resistance. For example, you could double the diameter of a ground electrode and your resistance would only decrease by 10%.
4. Complex ground system design
Complex grounding systems consist of multiple ground rods, connected, mesh or grid networks, ground plates, and ground loops. These systems are typically installed at power generating substations, central offices, and cell tower sites. Complex networks dramatically increase the amount of contact with the surrounding earth and lower ground resistances.
Why ground?
Poor grounding contributes to downtime. Moreover, a lack of good grounding is also dangerous and increases the risk of equipment failure.
Without an effective grounding system, you could be exposed to the risk of:
- electric shock
- instrumentation errors,
- harmonic distortion issues,
- power factor problems
- and a host of possible intermittent dilemmas
What to look for?
Addressing grounding problems requires testing the grounding system and then retesting after any corrections or modifications.
Pay particular attention to:
- corrosion in ground rods and their connections due to exposure to moisture, salt and fluctuating temperatures.
- a year-to-year increase in resistance of 20 percent
These red flags should be investigated immediately.
It's good to be grounded…
If fault currents have no path to the ground through a properly designed and maintained grounding system, they will find unintended paths that could include people.
Therefore, structures with properly grounded electrical systems are critical to the safety of people and equipment, giving current from a lightning strike or utility overvoltage a safe path to earth.
Whether simple or complex, grounding systems require periodic testing to ensure their readiness.
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