Grounding Phase: Explaining Star Configuration

[Sparks]

<Moderator's note: Thread split off from https://www.physicsforums.com/threa...uches-earth-ground.800587/page-4#post-5704259>

Why can a phase be grounded without blowing up such as in a star configuration ?No one has answered this sufficiently or simply.

 

[Averagesupernova]

Can you describe the scenario in more detail?

 

[Babadag]

It depends on how neutral was treated: ungrounded, high resistance grounded, low resistance grounded, reactance grounding, resonance grounding, solid grounding...
Low voltage systems are solid grounded-usually- then the phase-to-ground fault current is elevated.
High-resistance grounded, ungrounded and resonance grounded the fault current is weak.

 

[Windadct]

Since you reference a "Star" configuration, do you man in a delta ? --- On any grounding issue, try to draw the scenario, I think it will help here.

 

[Babadag]

Even in delta connected transformer secondary the capacitive current from the transformer windings to ground and mainly from cables-all around low voltage cable could discharge 100 mA to ground if it is well insulated. A weak insulation may rise the current reducing the resistance to ground.
Medium voltage cable-systems [4-36 kV] usually high resistance grounded-the capacitive current could reach a few amperes.
The ground potential is high but the impedance-or capacitive reactance-is high too.
So, beware, do not touch the live conductor even if it is low voltage.

 

[nand arora]

yes, you can ground a phase but only if you have not grounded your neutral wire ( which may be solidly or high resistance) otherwise it will lead to Line to ground falut current.

If you have not grounded neutral and you ground one of your phase wire, neutral will develop voltage w.r.t ground. your other two line to Earth voltage will also increase by 1.732 times as compared to when your neutral was grounded.

All the above is about star end of transformer

 

[jim hardy]

Why can a phase be grounded without blowing up such as in a star configuration ?No one has answered this sufficiently or simply.

In a pm i pointed Sparks toward this old thread . It has an exaggerated simplicity factor.
https://www.physicsforums.com/threads/alternating-current-live-and-neutral-wires.892309/

Improvements are welcome.

old jim