Ground to Neutral Voltage

It's kind of arbitrary to set a minimum value for a "system" without knowing what the "system" consists of.

If you are running 10 or more three phase motors of varying capacites and loads...then things get complicated.

Just throwing those numbers out there doesn't mean much to me.

What are your ground field readings?

ground reading values are 2ohm.

The reason you have any voltage difference between neutral and ground is because you have current flowing on the neutral. Why did you choose 0.2 volts. 0.6 is not much.

Check here http://cr4.globalspec.com/thread/77212#newcomments

Thanks for the reply.we have cep stabilised laser system.for properfuntioning of the laser system we need less than 0.2 volts.if it is more then the system does not work properly.

VEry strange, what kind of equipment are designed to work within voltage range of Neutral and Earth !! Are you sure?

Some imbalance in 3 phase system is perfectly normal, you cant get perfect balance.

Oh...now that sounds like a good reason!

according to comany specs its should be less than o.2volts.

The voltage between the Neutral and Ground depends on the distance (Resistance) of the nearest Grounding point. (Normally at the switchboard/ Fuse box).

IF the voltage (between Ground and Neutral) is too high, there may be some faulty appliance (creating a fault current to ground) causing an imbalance.

Also: the position of the 'Grounding Rod' needs to be checked.

Permissible Resistance varies in different countries/ states (check local regulations).

Thanks for the good suggestion.i will try to check this points.

The use of an isolation transformer is a good idea. That may solve all his issues by itself, but this seems to be very sensitive equipment that he is hooking up.

In broadcast facilities, I have designed and installed separate critical load, generator, and main distribution panels. They can be a pain to set up but are well worth the effort. Along the way, I have been taught some hard lessons that may be of use to anyone setting up sensitive equipment.

The generator is never big enough to run everything, so it's loads must be separated from the main building. Included should be the critical loads plus hallways, bathrooms, exit lights, security systems, and some lighting in critical equipment rooms and studios. If possible, the break room refrigerator and water coolers are welcome during a long outage due to, say, a hurricane. Radio and TV stations need to stay on the air during outages. And don't forget to include the engineering workbench and shop. Where else are you going to fix the broken stuff during the storm?

Air conditioners can be a real problem for a generator. The start-up current can be a real deal breaker. This problem can even sneak up on you. I was doing an extended test of our emergency circuits one weekend. I killed the main disconnect to the building, and everything seemed to be fine. We stayed on the air, and I started working on a project in my workshop. Suddenly the lights blinked out, and I heard a sound that I can only describe as a cross between a scream, and the wail of a tortured demonic spirit. This lasted for only a few seconds, then everything was back to normal. I started looking around, but couldn't find anything wrong. Then about ten minutes later it happened again. It turned out that a five ton air conditioner was trying to start it's compressor. It overloaded the generator, and caused the voltage to drop so low that everything went off. The HVAC unit had a time delay relay installed that prevented the compressor from starting for ten minutes after a power outage. This protects the compressor from trying to start up against a full head of pressure after a short power glitch. Our earlier system tests, had all lasted for less than the ten minutes of the "delay before make" time delay relay.

The sound I heard was the 30 KW generator. It was a direct drive generator connected to a natural gas fueled engine. It was inside of it's environmental enclosure, 50' outside of the brick building, on the other side of our on air studio from me. The studio had one modestly sized, double pane 1/4" thick glass, sound trap designed window set in double walls built with two isolated frames, triple layered sheetrock, and with 12" of sound absorbing insulation between them. This building and studio were so sound proof that we never heard any airplanes, even though we were in the main glide path for one of the runways of Houston Intercontinental Airport, and planes were only a few hundred feet high when they went directly over us. I still don't have any idea how that generator made that much noise.

The critical circuits must be generator backed up, but further, they must be better protected from surges, over and under voltages, and outages. That protection can include multiple and better surge protectors, ferroresonant transformers, full time uninteruptable power supplies, enhanced chemical grounding systems, and dedicated distribution panels.

One last thing for my soap box for today, when installing surge suppressors, keep in mind that surges caused by lightning happen very, very fast. These surges are so fast that in some ways they act like radio frequency signals. This means that they don't like to make sharp turns, don't make neat 90 degree angles in the wires. They also happen so fast and the voltage is rising so fast that the length of the wires between the suppressor and the protected circuit becomes critical. It takes time for the spike to travel along the wire and because the plot of the voltage rise is almost vertical, the difference of a few inches can make a great difference in the voltage passed on to the protected circuits.

This particular issue has been covered in CR4 many times. To describe a repetition of it as tiresome would be an understatement.

http://cr4.globalspec.com/thread/77245/IMP

hello rodney , to reduce that neutral / ground voltage to have a 6meters ground rod that if you are in wet ground but if you are in a dry or desert location you need 12 meters deep hole and to make a good grounding result you need to cut bronce plate littlebit the size of your hole and put it insde the hole flat position and next your ground rod and get 3 bucket of chacoal pulborized it ang then mix in two bucket of salt then pour on the grounding hole get two bucket of water pour it together then next the soil that way you can si the good result of your grounding system. this we are using in high voltage transmossion line grounding system,

hope this will make your jod done !!!!