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ELECTRICITY GROUNDING, Basics

ELECTRICITY GROUNDING, Basics

ELECTRICITY GROUNDING, Basics

(OP)
When i searched for the grounding details i found the line saying that "The thing to understand about electricity is that it is always looking for the shortest path back to the earth"..........Now i dont know what it mean....can somebody help me to understand this in a detail......
in a way like some mechanism....like electricity flows due to voltage difference...which i believe brings two terminals..... which means we have two terminals at power station and two terminals at sub station and two terminal at home and two terminal at our electrical appliance....so when i switch on the my appliance, that voltage difference in power station making my appliance run( i belive i am correct about this).......so where does grounding comes???

RE: ELECTRICITY GROUNDING, Basics

Your appliance is connect to a voltage source on one side (your supply) and to a neutrel on the other end - which is eventually grounded. You can never know what the voltage at any point of a circuit it is without referencing it to something. It is implied that references are typically other voltage supplies or grounded parts of the circuit. When you turn your appliance on you have created an electrical circuit between the supply and the grounded neutral circuit, with the appliance (or load) in between them. The load is the resistance part of the circuit. The potential difference between your source and neutral (ground) will cause current to flow. The load (resistance) between them will determine how much current flows.

Every electrical circuit must be just that - a circuit. A continuous loop where the electrons can always find there way 'back home.' Without a loop you have no circuit, and no current.

RE: ELECTRICITY GROUNDING, Basics

Dear Mechnaical,

Think of the voltage as a pressure. Friction in the pipes as resistance and the current as well...current. It does not matter if the pressure is positive or negitive it will always try to move to the equilibrium at atmospheric. Electricity does the same. Valves are switches. Solenoids are relays or contactors. The problems come when it becomes AC (Alternating Current) and now the resistance has some other factor which mix it up. It is like hydrosphers and dampers.

To transport electical energy we do it at high voltages (pressure) just like an HP steam line. High pressure thicker walls but smaller pipes. Electrically this is bigger insualtion and thinner conductors. When it get to the end we use transformers to change the voltage to a more friendly medium. Like running steam through a turbine and then using the exhaust steam to run a cooking or heating process.

The watts never change (other than losses) 10 000 watts (10 kilowatts or 10kW) and 1000v is 10Amps. W = IV. Watts = volts x amps. If on the low voltage side at 10v then the current would be 1000A. We won't get into three phase as it will really mess your mind. Let the bright sparks work with it. Sorry couldn't resist that.

RE: ELECTRICITY GROUNDING, Basics

"Looking for the shortest path to earth." This is a myth that makes some believe the earth is a big sponge trying to suck up all things electrical.

Does the earth conduct electricity? Yes it can, not because it is a good conductor, but because it is so massive.

Does the earth attract electricty? No. Unless a storm has created localized charge concentrations that get equalized by a current stroke from a local group of opposite charges in the atmosphere, commonly called lightning.

Do most electrical systems operate with some point connected to earth for safety and other resons? Yes.

Does that earth connection allow current to flow in the earth if another part of the system at a different potential comes in contact with the earth? Yes.

Is it good to have current flowing in the earth? No. Current should flow in the wires normally, and only in bonding/earthing conductors during faults.

Will a 5 gallon plastic bucket of sand holding a 3 meter copper ground rod provide a suitable safety ground for welding on an elevated metal platform by sucking up all the stray electricity? No. But our welders in Dubai believed this was true. They were victims of the "earth is a sponge" myth. Their scheme only worked because the rod fell over and contacted the steel handrail. Our site safety criteria required them to drive a ground rod if no suitable ground connection was available.

RE: ELECTRICITY GROUNDING, Basics

The other problem with "takes the path of least resistance" sounds like the electricity takes ONLY the path of least resistance, when it actually takes all available paths in different amounts based on resistance. This is obvious to everyone on this board, but it's a pet peeve of mine when talking to the ill-informed.

RE: ELECTRICITY GROUNDING, Basics

Wait until you tell them it's actually the 'holes' moving around and not the electrons! Even for experienced engineers sometimes it's best to not think about that stuff too hard.

RE: ELECTRICITY GROUNDING, Basics

Quote (rcwilson (Electrical))

Our site safety criteria required them to drive a ground rod if no suitable ground connection was available.

On the other hand, I'm facing a real-worl problem at my house where the "solid rock" underground is only 6 inches below the dirt? How do I get a "ground" connection to the required 6 foot long copper stake when there is no "ground" outside "underground"? 8<)

RE: ELECTRICITY GROUNDING, Basics

Common enough problem in the middle east. Have a google on how cathodic protection crews install groundbeds in rocky ground. If you really need that earth electrode. winky smile

RE: ELECTRICITY GROUNDING, Basics

Will do.

RE: ELECTRICITY GROUNDING, Basics

Quote (racookpe)

How do I get a "ground" connection to the required 6 foot long copper stake when there is no "ground" outside "underground"?
We have similat problems where I am. It's really difficult to get any kind of a grounding connection when the ground is frozen most of the year (or in some cases - all of the year)

Scotty - Most of the cathodic protection groundbeds I've seen (pipeline protection) involve multiple 300ft drilled wells filled with cast iron pigs and coke breeze. However, highly likely the issues with sand and rock are significantly different than arctic and permafrost ~(smile

If you are looking for physics: Get a copy of Soares Grounding and Bonding. You are looking for the details on a Ufer ground.

If you are in the US and the concern is meeting code - look at Concrete-encased Electrodes. This answer is not engineering. It is just code compliance. Perhaps look at an NEC handbook.

If the issue is lightning protection, probably still looking at CEE

And then there is the time honored tradition of excellent engineering - steal every good idea you see or hear of (always give credit and it isn't plagerism) Assuming there are other dwellings in the area - what did they do?

ice

Harmless flakes working together can unleash an avalanche of destruction

RE: ELECTRICITY GROUNDING, Basics


Let me heartily recommend the book: "Grounding electrical distribution systems for safety" by Eustace C Soares (1966).

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