Earthing, grounding and bonding
Hello folks,
I'm always stuck on the differences between earthing, grounding and bonding; especially for portable diesel generators and fixed generators (backup power for buildings).
Need your insight on the following please:
1. What are the differences of these terms, earthing, grounding and bonding (please consider someone coming from non-engineering background).
2. What are the requirements if earthing, grounding or bonding is a must for portable generators?
(How deep the rod, type and size of rod?).
Need examples and details from your own experience especially for construction diesel generators and temporary cabinets onsite. ..
Thanks in advance.
Comments (3)
Earthing and grounding are terms for basically the same thing. A connection to the ground. Bonding in connecting an insulated component to another component so they have the same static potential. 1: You can ground both components independent of each other. 2: You can ground one component and bond the other to the grounded component. 3: You can bond both grounded components to each other. Check out NFPA 77 for requirements.
Grounding/earthing is definitely a complicated concept, and isn't intuitive at all. The reason for that is that the concept of voltage isn't intuitive. When we talk about volts, we're not talking about some constant value that is the same everywhere like a kilogram would be. Volts are electrical potential, or the difference in electrical potential between two points. If you took a multimeter set to measure low voltage, and you touched two random isolated conductive objects, you would likely see a value displayed. If you touched the first object and then a third isolated conductive object, you'd see a different value. What you're measuring is the difference in electrical potential between those objects.
One way to visualize it is to think about height or altitude. The higher up you are, the more potential energy you have in falling back to the ground. Height and altitude are only meaningful when we have a reference point. Often when we talk about altitude, we talk about distance above sea level. When we think about falling, we only care how high above the local ground we are. Falling from 5000 feet above sea level in Florida would almost certainly be fatal. Falling from 5000 feet in Colorado might mean you tripped on your shoe lace.
Electrical voltage is the same. 100 volts might be like being 100 feet above the ground. It doesn't matter that 100 feet above the ground in Colorado might be 5100 feet above sea level and 100 feet above the ground in Florida might be 100 feet above sea level. You can't fall from Colorado to Florida.
Your height above the ground is your voltage and the ground is the ground.