bonding to power pole

[Jhaney]

In general when placing copper or fiber armoured cable along a power route we bond the cable sheath or armour to the power company's #6 awg grd wire to keep our plant at the same potential as the power co.'s.
But in an area I'm not overly familure with I was told we do not bond to the power comany's grnd but place 3 our own ground rods and bond to them. The reason being is the power company is running a Delta system where their ground is their neutral. So I'm lost how does their ground being their neutral make a difference? I don't know if its my sinus headache or what but I can't wrap my head around this, any help explaining this or reasoning it out would be greatly appreciated....

 

[don_resqcapt19]

I would expect that the NESC requires all of the systems on a common pole to be bonded together. Also a power company delta system does not have a neutral. A wye system has a neutral.

 

[Jhaney]

Ok going from what I remember in class since I never worked for any power company, but doesn't the 3 phase delta power systems go to 3 phase customer and to substations? This pole is in a residental area (didn't take a picture I know I'll kick myself later :dunce with 2 wires on the cross arm and one on the pole. The one wire on the pole is bonded to the #6awg wire running down the pole to the either ground rod or ground plate on the bottom of the pole. So being told that everything in their system is a Delta system doesn't seem correct to me. I guess I'm going to have to take a road trip and look at it again just to satisfy myself.

 

[don_resqcapt19]

You can feed a single transformer to supply single phase power from a delta primary distribution system. You would just use two phases of the 3 phase delta to feed the transformer. With a wye distribution you can either use two of the 3 phases or one phase and the neutral to feed the primary of the single phase transformer.

 

[Hv&Lv]

That isn't a delta system. It is two phases feeding a residential area. The neutral is the one on the pole. NESC rule 97 and 98 address bonding communication lines to power poles. You can install your own ground rods, but they (by NESC) must be bonded to the pole. If they are seperate, but the grounds rods are fairly close together, it will cause problems later.

 

[Jhaney]

I thought that was correct but quite wrap my brain around it due to sinus headache. Now I just have to convince the higher up.

 

[kwired]

It really makes no difference if the system is wye or delta - if one of the conductors is grounded you treat the grounded conductor the same in either system.

If your communications is connected to multiple structures also attached to the power system you will have current flowing on your shield if there is current on the grounded conductor you connected to. There is really no way to avoid this other than to not run to places where there is also power lines present. Not going to happen there will at very least be power at each end of the communication cable in almost all cases.

 

[robbietan]

Ok going from what I remember in class since I never worked for any power company, but doesn't the 3 phase delta power systems go to 3 phase customer and to substations? This pole is in a residental area (didn't take a picture I know I'll kick myself later :dunce with 2 wires on the cross arm and one on the pole. The one wire on the pole is bonded to the #6awg wire running down the pole to the either ground rod or ground plate on the bottom of the pole. So being told that everything in their system is a Delta system doesn't seem correct to me.

probably an open delta system.