Grounding Phase: Explaining Star Configuration

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SUMMARY

The discussion focuses on the grounding of a phase in a star configuration without causing catastrophic failures. It emphasizes the importance of how the neutral is treated, with options including ungrounded, high resistance grounded, low resistance grounded, reactance grounding, and resonance grounding. In low voltage systems, solid grounding typically results in elevated phase-to-ground fault currents, while high-resistance grounded systems exhibit weaker fault currents. The conversation also highlights the implications of grounding a phase without grounding the neutral, which can lead to increased line-to-earth voltages.

PREREQUISITES
  • Understanding of grounding techniques: solid grounding, high resistance grounding, and reactance grounding
  • Knowledge of electrical configurations: star and delta configurations
  • Familiarity with fault current behavior in electrical systems
  • Basic principles of capacitive current in low and medium voltage systems
NEXT STEPS
  • Research the differences between solid grounding and high resistance grounding in electrical systems
  • Learn about the implications of grounding configurations in star and delta transformer setups
  • Study the effects of capacitive current on grounding and fault currents in low voltage systems
  • Explore the safety measures for handling live conductors in grounded and ungrounded systems
USEFUL FOR

Electrical engineers, safety professionals, and technicians involved in power distribution and grounding practices will benefit from this discussion.

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Can you describe the scenario in more detail?
 
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.
 
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.
 
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.
 
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
 

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