improving earth conductivity


Thread Starter

thiagarajan sriram

We have got electronic weighbridges in our steel plant. We have provided separate earth pits for Power supply and load cells. During rainy season and heavy lightning strikes the digital weight indicators, load cells and the computers are getting damaged. We checked and found the earth to neutral voltage is varying between 4 volts to 7 volts. I would like to have following clarifications regarding this.

1. For electronic equipment earth pits the earth to neutral voltage should not be more than 1 Volt. How to minimize this voltage?

2. When we tried to apply water to the earth pits water is not being absorbed quickly. It takes more time. How to solve this problem?

3. Can we improve the earth conductivity by adding charcoal, salt, bentonate clay etc to earth pits?

4. Our earth pits depth is 10 to 12 feet only. If we go more deeper (50 feet) can we get more conductivity?

5. If we increase the number of earth pits and by forming a network can we increase earth conductivity?

6. We have got earth resistance tester. When we checked earth resistance as per the procedure shown in the manual we got earth resistance values more than 3 ohms which is not within permissible limits. Our test electrodes were driven to a depth of one meter only. Should we drive the same more deeply( 2 meters)?

7. Once during lightning we switched off the power supply to the weigh bridges but still the load cells got damaged. We are planning to have three spike, brass lightning arrestors on each weigh bridge to protect load cells against direct lightning strokes. Will it be sufficient Or any other method can be adapted?

Pl clarify these points.

bob peterson

The earth to neutral voltage is controlled by the current in the neutral leg. If there is neutral current, the voltage to earth cannot be zero. You cannot get around Ohms law.

You can "improve" your earthing system until you run out of money but it will never do anything to protect your instruments from lightening strikes.

There are a bunch of products sold that will actually help in this regards.

I would start there, and stop obsessing over your earthing system.


C Shekhar Mgr HSM

One reason for damage due to lightening strikes is the flow of spikes in phase, neutral and ground. Install a protective sheet of lightening arrestor.

The surge arrestor in power supply transformer is probably not working.. Because the electronic equipments are getting damaged even in power off condition.

i am having a similar issue with voltage varying from 3 v to 8 v . have you found a solution to your issue.


anil utturkar

check the phase neutral voltage it should be balanced. if not arrange the load balance such that all phase currents are same. then you will get less voltage between earth and neutral.

William \(Bill\) L Mostia Jr PE

> Do we need 1 earthing for 1 meter?
> or
> Can we put 1 earthing for 2 meters?

You need to provide more information and/or description of what your problem is or what you are trying to accomplish before the members of this mail list can help you. For example, are you trying to improve actual earth conductivity, talking about ground rod depth, or trying to improve your grounding system?

William (Bill) L. Mostia, Jr. PE
Sr. Consultant
SIS-TECH Solutions, LP
Any information is provided on Caveat Emptor basis.