Ungrounded Delta Votage to ground

[bobby ocampo]

What is the voltage to ground for a delta connected one leg with center tap if the line to line voltage is 240 volts?
a. Voltage of line 1 to ground?
b. Voltage of line 2 to ground?
c. Voltage of line 3 to ground
d. Voltage of center tap in one leg to ground?

What will be the voltage to ground if the delta is corner grounded?
What is the voltage to ground if the delta is center tap in one leg grounded?

 

[LarryFine]

If ungrounded (floating):
a. Random
b. Random
c. Random
d. Random

With L1 corner-grounded:
a. 0.0 v
b. 240
c. 240v
d. 120v

With CT of L1-L3 grounded:
a. 120v
b, 208v
c. 120v
d. 0.0 v

 

[bobby ocampo]

If ungrounded (floating):
a. Random
b. Random
c. Random
d. Random

With L1 corner-grounded:
a. 0.0 v
b. 240
c. 240v
d. 120v

With CT of L1-L3 grounded:
a. 120v
b, 208v
c. 120v
d. 0.0 v

Have you experienced testing the voltage to ground for a delta ungrounded system?

For corner grounded have you tried checking the voltage of neutral to ground? Please check
Have you observe that when a current carrying conductor is grounded the voltage to ground is zero? If the line to ground voltage is zero do you have a probability of being electrocuted if you touch the grounded conductor or connected to earth?

 

[augie47]

Ungrounded systems were fairly common in industrial facilities in this area, corner grounded not so much.
On ungrounded systems, depending on the type meter used, you can get a variety of meaningless voltages some exceeding the phase-phase voltage.
On corner grounded systems, connecting the one phase to earth does not pose a shock hazard s there is no current path. It would be similar to connecting the - on a battery to earth. (Corner grounded systems do provide an "extra" shock potential to the other non-grounded phases as the potential is the same as a phase to phase voltage). Bonding of equipment is important.

 

[jim dungar]

Have you observe that when a current carrying conductor is grounded the voltage to ground is zero? If the line to ground voltage is zero do you have a probability of being electrocuted if you touch the grounded conductor or connected to earth?

I have observed many times when there is a voltage difference between the grounded and the grounding conductor. It is dependent on the length of the conductor from tge grounding point, the common connection, and the point of contact. Current flowing through the grounded conductor will cause a voltage drop, which may result in the two conductors not being at the same potential for their entire length.

 

[LarryFine]

Have you experienced testing the voltage to ground for a delta ungrounded system?

Yes. While capacitance tends to make the system measure like a grounded-wye system, especially with a high-impedance meter, any appreciable load to ground on any line will readily bring that line close to 0.0v.

For corner grounded have you tried checking the voltage of neutral to ground? Please check

Again, yes. The "neutral" (intentionally-grounded conductor) of a corner-grounded system will measure and behave just like the neutral in any intentionally-grounded system.

Have you observe that when a current carrying conductor is grounded the voltage to ground is zero?

Well, at the location of the system bonding jumper, which effectively defines the service's or SDS's zero-voltage point, it will obviously measure 0.0v. As you work your way towards loads from there, when the grounded conductor must not be re-grounded, some voltage is likely.

Loading on the grounded conductor downstream from that bonding point will tend to cause voltage drop, which always raises the voltage to ground on a corner-grounded delta, and with imbalanced loading on systems where the grounded conductor is a genuine neutral.

If the line to ground voltage is zero do you have a probability of being electrocuted if you touch the grounded conductor or connected to earth?

Well, I believe you're using "electrocuted" to mean any shock. If you're measuring zero volts between two points, there is zero risk of shock, as no current can be made to flow. You can go outside and touch your electric meter while standing on the ground barefoot with no risk.

 

[LarryFine]

Just as we size line conductors to minimize voltage drop, in order to attempt to force all of the voltage to be dropped across the intended load, we likewise size grounded conductors for the same reason. We want the voltage at the load to remain as close as we can to what it is at the source.

That means that we want the voltage at the load end of the intentionally-grounded conductor to be as close as it can be to zero volts to earth as possible, even under load. However, we're realistic enough to realize that it will rise at times, which is why, except for OCP, we treat it like a line conductor.

See: https://forums.mikeholt.com/threads/understanding-the-neutral-conductor.140537/

 

[bobby ocampo]

Ungrounded systems were fairly common in industrial facilities in this area, corner grounded not so much.
On ungrounded systems, depending on the type meter used, you can get a variety of meaningless voltages some exceeding the phase-phase voltage.
On corner grounded systems, connecting the one phase to earth does not pose a shock hazard s there is no current path. It would be similar to connecting the - on a battery to earth. (Corner grounded systems do provide an "extra" shock potential to the other non-grounded phases as the potential is the same as a phase to phase voltage). Bonding of equipment is important.

Please comment on the topic. What are the voltages to ground and we will know the answer? This electrical engineering subject will show us the importance of equipment grounding and understand connecting to the earth.

 

[bobby ocampo]

I have observed many times when there is a voltage difference between the grounded and the grounding conductor. It is dependent on the length of the conductor from tge grounding point, the vommon connection, and the point of contact. Current flowing through the grounded conductor will cause a voltage drop, which may result in the two conductors not being at the same potential for their entire length.

What happens if at the end of the neutral it is grounded again?

 

[bobby ocampo]

Yes. While capacitance tends to make the system measure like a grounded-wye system, especially with a high-impedance meter, any appreciable load to ground on any line will readily bring that line close to 0.0v.

Please test again. It is not zero or approaching zero. The question did not say to have a load to ground just requiring what is the voltage to ground

Again, yes. The "neutral" (intentionally-grounded conductor) of a corner-grounded system will measure and behave just like the neutral in any intentionally-grounded system.

Given is corner grounded. What is the voltage to neutral if delta is corner grounded?

Neutral in wye connected system behaves differently

Well, at the location of the system bonding jumper, which effectively defines the service's or SDS's zero-voltage point, it will obviously measure 0.0v. As you work your way towards loads from there, when the grounded conductor must not be re-grounded, some voltage is likely.

Loading on the grounded conductor downstream from that bonding point will tend to cause voltage drop, which always raises the voltage to ground on a corner-grounded delta, and with imbalanced loading on systems where the grounded conductor is a genuine neutral.

The connection of the neutral other than the service equipment is another issue I want to clarify later in other topic. What I want to show is grounding reduces if not eliminate the potential to zero or near zero by connecting any line to ground.

Well, I believe you're using "electrocuted" to mean any shock. If you're measuring zero volts between two points, there is zero risk of shock, as no current can be made to flow. You can go outside and touch your electric meter while standing on the ground barefoot with no risk.

Of course I mean electrocuted. death due to electric shock. I want to prove the connecting to earth helps prevent electrocution or minimize shock.

 

[jim dungar]

What happens if at the end of the neutral it is grounded again?

Then it becomes a violation of the NEC.

 

[__dan]

Of course I mean electrocuted. death due to electric shock. I want to prove the connecting to earth helps prevent electrocution or minimize shock.

Properly installed, Earthing a system does nothing. It would be easier to prove that.

Grounding a system otoh is intended to trip the upstream protective device in the event of shorts and ground faults. Bonding, grounding, and the system bonding jumper is what prevents shocks (by tripping the upstream device).

 

[LarryFine]

What happens if at the end of the neutral it is grounded again?

You run the risk of energizing surfaces normally expected to be at zero volts to earth.

 

[LarryFine]

Please test again. It is not zero or approaching zero. The question did not say to have a load to ground just requiring what is the voltage to ground

It can be anywhere from zero to the primary voltage.

Given is corner grounded. What is the voltage to neutral if delta is corner grounded?

While technically not a neutral, the answer is still zero.

Neutral in wye connected system behaves differently

Yes, and technically it is a neutral.

The connection of the neutral other than the service equipment is another issue I want to clarify later in other topic. What I want to show is grounding reduces if not eliminate the potential to zero or near zero by connecting any line to ground.

Of course it does, to the extent capable by the impedance of the "grounding" method. Earth alone is the worst.

Of course I mean electrocuted. death due to electric shock. I want to prove the connecting to earth helps prevent electrocution or minimize shock.

That may prove to be a little more difficult. Earthing the electrical system simultaneously causes and resolves different safety aspects. GFCIs, for example, are both required by, and depend upon having an earthed system.

Note that we're discussing why we have a supply conductor tied to earth via electrodes, and not why we have a supply conductor bonded to an equipment-grounding conductor. That's another topic entirely.

 

[__dan]

Have you experienced testing the voltage to ground for a delta ungrounded system?
...

If the line to ground voltage is zero do you have a probability of being electrocuted if you touch the grounded conductor or connected to earth?

We have grounded systems for exactly this reason of how the next person looks at it (and what may happen if he has to work on it with his own hands, touching).

If you're touching the grounded conductor and you don't know what you're doing, yes, you have a significant probability of being electrocuted. Trying that same thing on a floating delta, only assures the probability of shock increases. Why would you touch it, the grounded conductor. You may want to turn it off if you have to work on it, touch it.

That's where grounded systems are necessary. They will turn the thing off for you, indicating it needs to be worked on.

 

[__dan]

Distributing three phase three wire without an equipment grounding conductor using only local Earth grounds, "peg grounds" in this report, is a known cause of fatalities.

Lack of the equipment ground does not trip the upstream device and the exposed remote metal floats at the line Voltage, including the earthing system. The worker completes the circuit from the floating exposed metal, to the Earth.

MSHA - Technical Reports - MSHA METAL/NONMETAL ELECTRICAL GROUNDING REQUIREMENTS

Federal enforcement agency responsible for the health and safety of the nation's miners.

arlweb.msha.gov

 

[zbang]

I've been staying out of this and perhaps I'm missing something, but what is the purpose of this discussion? It's not clear whether the OP is trying to answer a test question, is trying to teach something to those who already know the subject, advocating a particular grounding method, or what.

 

[bobby ocampo]

Then it becomes a violation of the NEC.

Have you tried measuring the voltage to ground?
What if the connection of the neutral to earth is not connected in the transformer but in the distribution panel? What will be the voltage to ground from the neutral to ground?

 

[bobby ocampo]

Properly installed, Earthing a system does nothing. It would be easier to prove that.

Are you sure? Does electricity in ungrounded conductor have a different principles than in solidly grounded?

Grounding a system otoh is intended to trip the upstream protective device in the event of shorts and ground faults. Bonding, grounding, and the system bonding jumper is what prevents shocks (by tripping the upstream device).

Are you sure this are the only reason for connecting to earth? Have you checked IEEE 80?

 

[bobby ocampo]

We have grounded systems for exactly this reason of how the next person looks at it (and what may happen if he has to work on it with his own hands, touching).

We still allow ungrounded systems for continuity of service specially in low voltage where HRG is not economical. Code is not prohibiting the use of ungrounded system. It may have disadvantages but solidly grounded has disadvantages too. IEEE 142 chapter 1

If you're touching the grounded conductor and you don't know what you're doing, yes, you have a significant probability of being electrocuted.

What is the purpose of a voltmeter in checking if a conductor or equipment is energized?

Trying that same thing on a floating delta, only assures the probability of shock increases. Why would you touch it, the grounded conductor. You may want to turn it off if you have to work on it, touch it.

Have you tried checking the line to ground voltage using a voltmeter? Will you be shock with zero voltage of very low voltage to ground?

That's where grounded systems are necessary. They will turn the thing off for you, indicating it needs to be worked on.

Have you not experienced an ungrounded system specially in hospitals and other industrial installations where continuity of service is required for a specific equipment?