Electronics > Projects, Designs, and Technical Stuff

Earthing mains power supply

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Monkeh:

--- Quote from: treez on June 28, 2020, 01:03:32 pm ---
--- Quote ---one of the problems with any tnc type supply is if the  neutral earth bond goes missing at the sub station,the return current will travel by any route it can to earth,if you have extra rods installed giving a nice low impedance path to earth the majority of the return currents for the network may end up with you.
--- End quote ---
Yes, this is the bad situation, if neutral and earth are not connected at the sub-station due to some fault there...however, this will result in dangerously high mains live voltages which will result  in blown MOVs in many  mains plugged devices in your house, and your  house supply fuse would  likely blow.

Im pretty certain most house electrical junction boxes have mains voltage detectors in them which switch off the supply if it goes too high in voltage.

--- End quote ---

treez, you have absolutely no idea what you're talking about.

David Hess:
Where I live not far from St. Louis, Missouri, several houses in a row along the power distribution lines use the same pole transformer and each of them has their own ground rod connected to neutral at their primary distribution box so there are several ground rods tied to the same neutral over hundreds of yards.  The areas in California where I have lived did exactly the same thing.

When I installed several chimney mount antennas, I considered the existing power ground rod completely inadequate for lighting protection so I installed my own 10 foot length of 1/2" copper pipe at the base of the chimney and filled it with salt.  (1) Where I have seen shacks for radio gear at the base of antenna towers, they did the same at every corner of the shack while tying the rods all together.

(1) Use a fitting to attach a garden hose to the top of the pipe and use water pressure to hydraulically drill it into the ground.  This is much easier than pounding on it.

ocset:

--- Quote ---treez, you have absolutely no idea what you're talking about.
--- End quote ---
Woops yes sorry, I was thinking of a lost neutral conductor in a 3 phase system (as you know all domestic mains originates from 3 phase at some point)…….the consequences of a lost neutral conductor will vary, depending mainly on the load balance conditions in the three phase system, but also on the type of earthing system used and the position of the break in the neutral relative to the load.
Worst case scenarios could include both damage to connected loads due to overvoltages on single phase circuits or the creation of hazardous touch voltages on exposed conductive parts.

Bassman59:

--- Quote from: akis on June 28, 2020, 07:22:59 am ---"I'll see your radiator clamps  and raise with bonding metal window frames in the bathroom."

If I understand correctly you are saying that one should only earth an electrical device that has a chance of exposing its live power to its metal chassis, but one should not earth a passive device like a radiator?

--- End quote ---

I read it as radiators (and the metal window frames) are a sufficient ground, rather than a proper ground going back to the panel.

Monkeh:

--- Quote from: Bassman59 on June 29, 2020, 04:43:53 am ---
--- Quote from: akis on June 28, 2020, 07:22:59 am ---"I'll see your radiator clamps  and raise with bonding metal window frames in the bathroom."

If I understand correctly you are saying that one should only earth an electrical device that has a chance of exposing its live power to its metal chassis, but one should not earth a passive device like a radiator?

--- End quote ---

I read it as radiators (and the metal window frames) are a sufficient ground, rather than a proper ground going back to the panel.

--- End quote ---

.. no, they're absolutely not.

There was some minor insanity regarding bonding every metal object you could possibly touch to earth. It was, indeed, insanity, and we now only concern ourselves with objects capable of introducing a (sufficiently low impedance) potential.

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