The electron man
Senior Member
- Location
- Nyc
- Occupation
- Electrician
So I was wondering if you had a delta delta transformer and one of the phase hit ground how would the current return to the source to trip the ocpd since you have no neutral ??
Delta Delta transformer
- Thread starter The electron man
- Start date
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Thus the need for a grounded secondary point (neutral or corner) or ground-fault detection.
ptonsparky
Tom
- Occupation
- EC - retired
It waited for the second to hit it.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Translation, if I may:
With an ungrounded system, the first unintentional ground fault would effectively make the system behave as an intentionally-grounded system, but with uncertain voltages.
Undetected, the system would likely continue to function until another ground fault occurred on a different system conductor, in which case OCPD should function as intended.
ptonsparky
Tom
- Occupation
- EC - retired
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
As she should be.
TwoBlocked
Senior Member
- Location
- Bradford County, PA
- Occupation
- Industrial Electrician
It won't. It's like taking a battery and connecting just one terminal to ground. Nothing happens. But if the other terminal also connects to ground, THEN current flows, and a lot of it.
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
One clarification: The presence or lack of a neutral isn't the key point here. It is the presence or lack of an intentionally grounded terminal that makes the difference.
In theory you can ground _any_ terminal of a transformer to create a grounded system; with a delta secondary you can create a corner grounded system or perhaps a 'high leg' system. Similarly, if you have a wye secondary you could leave all the terminals ungrounded and have an ungrounded system.
Code has some specific requirements; if you use the neutral as a circuit conductor it _must_ be the grounded conductor. So if you have a wye secondary and you are using the neutral you can't legally install this as an ungrounded system.
-Jonathan
In theory you can ground _any_ terminal of a transformer to create a grounded system; with a delta secondary you can create a corner grounded system or perhaps a 'high leg' system. Similarly, if you have a wye secondary you could leave all the terminals ungrounded and have an ungrounded system.
Code has some specific requirements; if you use the neutral as a circuit conductor it _must_ be the grounded conductor. So if you have a wye secondary and you are using the neutral you can't legally install this as an ungrounded system.
-Jonathan
The electron man
Senior Member
- Location
- Nyc
- Occupation
- Electrician
But a delta wye transformer would since its connected to the main service with a main bonding jumper that competes the circuit ??
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Only if/because there is a secondary system line, usually the neutral, that we "always" intentionally ground.
The premises EGC system is always grounded. The secondary system is usually, but not always grounded.
Tying the EGC system to the neutral assures that a line-to-ground fault behaves like a line-to-neutral fault.
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
You can install a main bonding jumper on the delta secondary of a delta:delta transformer.
The main bonding jumper is what creates the system grounding and completes the return current path, not the presence or absence of the neutral.
-Jonathan
ptonsparky
Tom
- Occupation
- EC - retired
Point being the Grounded conductor is not necessarily a neutral.