Test Isolated Ground Rod with Multimeter and Battery

No, not unless you have something else to connect it to, like a second ground rod.

No. That doesn't work. Most instructions for measuring "ground rod resistance" require that the electrical system already be installed. For your test, that's not available. Also, you're not really measuring the ground rod resistance, but rather the "soil resistivity". To do that, you need at least two ground rods.

"Earth Ground Resistance" Equipment page: Try the videos on the web page.

Hint: If you know the soil type and the rod is at least 8 ft long, you can calculate the resistance with sufficient accuracy to satisfy the electrical inspector.

Om europe at least you could just place a ohm meter from the rod to earth of a nearby installation. But it won't show you the exact earthing resistance since you are also measuring the rod in the existing system

Just out of curiosity, I have seen small electrostatic motors running from an antenna with a single connection to earth.

How much voltage potential is required to actually use the earth (single ground rod) as an electron source?

Robert Miller

It works if you have _two_ additional ground rods. That gives you three equations in three unknowns. (Four ground rods make an overdetermined system that supplies an internal error estimate.)

Cheers

Phil Hobbs

well the rod conducts to earth. "

Why ? You are doing the best you can. If it doesn't conduct enough just wha t are you going to do ?

They want it ten feet deep here, almost three meters. But even at two meter s, if a short happens and it puts mains voltage to ground it should start t o conduct enough to at least trip the breaker. They are not looking for a c onnection that would make Tesla happy, just something to enhance safety.

My advice is to just follow the electrical code and don't worry about this shit. That is for audiophools and other lunatics.

If this is a separate installation from the house, do not expect there not to be a difference between the grounds. While you do want the ground as nea r to the installation as possible, expect a difference between the neutral and ground. That is if it is say a garage and the power is coming from the house.

In the US, the National Electrical Code requires a ground rod be at least 8 ft in the earth. The maximum resistance-to-earth is 25 ohms. Or you can use 2 rods, no required resistance. Requiring more than 2 rods runs into the law of diminishing returns. Ground rods are among the worst earthing electrodes. What happens when you connect 120V (or 220V) to a code-compliant 25 ohm rod? For that reason an earth path is not allowed by the NEC to be used to trip a breaker. What is used is a N-G bond required at all services. With a short to ground, the current returns on the ground system to the service, then across the N-G bond to the service neutral, and back to the transformer. The all-metal path provides a high current to trip breakers.

A much better electrode that is often required for new construction is a "concrete encased electrode", often called a Ufer ground.

Some UK systems do not bond the neutral at the building and the return path is through the earth. I think that is why RCD main breakers are used.

Jeff's links cover how to measure resistance-to-earth.

Indoors the stray capacitance between mains wiring and a decent size "antenna" is in the order of 10-100 pF. If this "antenna" is grounded through an electrostatic motor, with low internal capacitance (less than 10 pF), this will form a capacitive voltage divider. With 10 pF of stray capacitance and 10 pF of motor capacitance, about one half of the mains voltage is across the motor.

For any "free" energy enthusiasts lurking here, calculate how much power can be taken through a 10 pF stray capacitance :-)

Such stray capacitance systems work best in single phase environment, since the electric fields from three phases (e.g. high voltage lines) tend to cancel each other, unless you position your device in a position in which there is a different distance to different phase conductors.

With such high resistance only 5 A would flow in a ground fault from

In TN-C-S earthing system, the TN-C part from distribution transformer CT (or star point in three phase systems) to the house entry uses a common PEN conductor. At house entry, this is split into PE and N and there is a TN-S system inside the house.

What happens if the common PEN conductor is broken and there is an unbalanced load ? In the house both the PE and N floats towards the phase conductor, depending of the load imbalance. In addition to damages to devices connected between a phase and neutral, there can be lethal voltages between PE and some outside grounded objects.

By connecting the PEN to PE and S split to a real grounding electrode, some of the inbalance current previously running through the PEN conductor will flow through the ground to the transformer CT/start point, which is well grounded.

It should be noted that this ground current of 5 A (120 V/25 ohm) represents the _difference_ of phase currents (both antiphase and three phase systems), keeping the in house PE difference potential from other real grounds within safe limits (50 V ?). This is not intended for handling full ground fault current, just the differential current due to unbalanced load currents.

In some countries a uninsulated loop is required around the perimeter os the house. Before building a house, dig this loop. Both ends of this contiguous conductor is brought to surface and this is connected to the split between PEN to PE and N.

This has an additional advantage if a lightning hits a nearby tree and the tree has roots under the house, most current will go into earthing loop. Without this earthing loop, lightning current can flow through the roots and then hit _upwards_ into anything in the house.