Electrical contact

[Thissguyy]

Hi I work in Ohio and we have a 13.2kv system. 7,620v phase to ground, this is a wye system. On a single bushing transformer we connect the transformer neutral tail to the system neutral and the pole ground, the neutral acts as the return for the system. If the transformer neutral is only connected to the pole ground and that connection is broken, what voltages could a person get if her completes that ground circuit? This is a 50kva single bushing 120/240 transformer. Thank you

 

[JoeStillman]

Welcome to the forum.

If the primary is connected on the line side and the neutral side of the transformer primary winding is not connected to anything, it will measure 7,620 V from the primary neutral terminal to ground. Grounding that neutral terminal will complete the circuit and magnetize the transformer with the inrush current flowing from line to ground - not something you want to do.

If that neutral tail is not connected to anything, open the primary cutout before you do anything else.

 

[Hv&Lv]

Hi I work in Ohio and we have a 13.2kv system. 7,620v phase to ground, this is a wye system. On a single bushing transformer we connect the transformer neutral tail to the system neutral and the pole ground, the neutral acts as the return for the system. If the transformer neutral is only connected to the pole ground and that connection is broken, what voltages could a person get if her completes that ground circuit? This is a 50kva single bushing 120/240 transformer. Thank you

You will have an open neutral condition.
That’s why it’s important to connect the neutral (middle bushing on secondary side) to the mainline. It’s also important to connect your load neutral to this lead also.
I have had to deal with house neutral connected to mainline neutral, then the transformer connected to mainline separate. One connection goes bad, open neutral.
Same thing with connecting this CSP pot neutral bushing to pole ground. That number 6 pole ground isn’t large enough to carry currents back to mainline.
The voltages you will see will vary with the loads in the house. A hairdryer or microwave will see upwards of 200V while the other leg will see a large drop in voltage.
Test with a hairdryer because it’s a big load and it’s cheap.
You guys have a “beast of burden”?

 

[Thissguyy]

So I asked the question because a transformer was tested and they only connected the transformer neutral tail to the pole down ground. The ground was not connected to the ground rod and someone drew that voltage between the ground wire and ground rod when they completed the circuit trying to connect it. This is not common practice but a mistake. Curious on potential voltage that person may have received?

 

[paulengr]

So I asked the question because a transformer was tested and they only connected the transformer neutral tail to the pole down ground. The ground was not connected to the ground rod and someone drew that voltage between the ground wire and ground rod when they completed the circuit trying to connect it. This is not common practice but a mistake. Curious on potential voltage that person may have received?

Pole grounds are poor at best. It’s basically just winding some extra wire around the pole butt before setting the pole. But every pole is grounded so the combined effect is pretty decent. Don’t consider them effective grounding because most of them
I’ve actually tested (3 wire test) are pretty lousy…tens to hundreds of ohms.

 

[LarryFine]

If the transformer neutral is only connected to the pole ground and that connection is broken, what voltages could a person get if her completes that ground circuit?

The entire 7,620, naturally. The primary impedance will have little effect on the voltage across the person's body.

With that earthing conductor still intact, you'd basically have an old-fashion SWER supply.

 

[LarryFine]

So I asked the question because a transformer was tested and they only connected the transformer neutral tail to the pole down ground. The ground was not connected to the ground rod and someone drew that voltage between the ground wire and ground rod when they completed the circuit trying to connect it. This is not common practice but a mistake. Curious on potential voltage that person may have received?

The transformer should not have been energized without the primary neutral connection made.

The habit of making up the EGC first, neutral second, line(s) last, should apply to distribution, too.

 

[Hv&Lv]

The transformer should not have been energized without the primary neutral connection made.

The habit of making up the EGC first, neutral second, line(s) last, should apply to distribution, too.

It’s taught like that, but not everyone follows suit.