delta to wye xformers

o.k, the power co. came and verified that which i suspected, that is their transformer is a delta over wye to feed a delta to wye in the facility.

they are supplying a "neutral" which is bonded to earth at the pole.

it is this "neutral" that i intend to use with a seperate earth, building and water pipe ground to bond the secondary neutral of each of four transformers in the facility and hopefully remove all current from the existing ground at the panels closes to their respective transformers.

Hey jerryalan,

Your distribution panels should have a neutral wire that ties back to your main panel. If the load between the three phases is not ballanced (and frequently it is not well ballanced) then there can be substantial neutral currents. This is due to the imbalance and consequently, neutral lines should be as big as the conductors with which they are paired.

Ground the neutral at various locations throughout the plant leads to an increased potential for ground faults and ground loops that can negatively affect instrumentation. In general, if you must connect to an earth ground in places, use a 10 foot copper rod driven into the ground. Using the water pipe is not the best solution.

My Friend,

NoturordinaryJoe is totally correct. In addition to his advice, include this.

* Fabricate 200mm(L) x 100mm(H) x 10mm(Thickness) of copper plate, drill holes with different diameter for your grounding and nuetral wire sizes, and terminate these top the copper plate.

* Copper plate should be float by means of insulation materials, mounted nearest to the source and against the wall adjacent to the electrical equipment (panels, MCC, x'former & etc).

* 70mm2 grounding cable with green insulation terminated from this copper plate to 3M long ground rod (don't forget the inspection pit/box.

The purpose of this is well-known to all power utility, oil&gas and large industrial plants to avoid unwanted grounding and unbalanced electrical potential to all electronic devices and easier way to maintain the system by means isolating all potential force of ground to other system.

Eren

Good catch Joe, in fact the bonding to the metal piping systems is only to bond them to ground in case the metal pipes become energized by a failure of a piece of equipment that affects them, and NOT to provide a ground path for panels or equipment. Pity the plumber that becomes the system ground during replacement of a faulty water heater etc.