Understanding CT and VT Saturation Effects

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Discussion Overview

The discussion centers on the differences in flux saturation effects between current transformers (CTs) and voltage transformers (VTs), particularly in the context of fault conditions. Participants explore the underlying principles and behaviors of these transformers during faults, including the impact of direct current (d.c.) components.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions why CTs experience flux saturation while VTs typically do not.
  • Another participant suggests that CT saturation is influenced by the d.c. component of fault current, which may not affect VTs in the same way during line faults.
  • A further contribution emphasizes that the magnetizing working point of VTs remains fixed under constant primary voltage, contrasting with CTs where the working point varies with changes in primary and secondary currents, leading to potential saturation during short circuits.
  • Some participants express skepticism about relying solely on internet sources without grounding in basic concepts, indicating a concern for the depth of understanding in the discussion.

Areas of Agreement / Disagreement

Participants express differing views on the mechanisms behind saturation in CTs versus VTs, with no consensus reached on the explanations provided. The discussion remains unresolved regarding the implications of d.c. components in fault conditions.

Contextual Notes

There are limitations in the discussion regarding assumptions about the behavior of transformers under fault conditions and the definitions of terms used, which may not be fully clarified.

metsfan1395
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Can anyone explain why a CT would be subject to flux saturation, but a VT normally wouldn't?
 
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Core saturation-of protective current transformers due to the d.c. component of fault current...
http://findarticles.com/p/articles/mi_qa3792/is_/ai_n8918425"

I would think that VTs would not see this d.c.component in its secondary during a line fault.

Welcome to PF
 
Last edited by a moderator:
dlgoff said:
http://findarticles.com/p/articles/mi_qa3792/is_/ai_n8918425"

I would think that VTs would not see this d.c.component in its secondary during a line fault.

Excuse me, I think internet searching or data gathering without referring to basic concepts cannot solve our problems. Of course this is the disadvantage of today information explosion.

Magnetizing working point of voltage transformers is fixed by applied constant primary voltage. This working point doesn't vary even in secondary short circuit fault condition.
However in current transformers, the magnetizing working point varies when the primary/secondary current changes; because the link voltage of this type transformer is variable and may change proportion to multiplying of CT secondary current and secondary impedance. Therefore the voltage level of CT may be increased very much (CT saturation) due to primary short circuit fault currents.

--------------------------------------
Creative thinking is enjoyable, Then think about your surrounding things and other thought products. http://electrical-riddles.com
 
Last edited by a moderator:
m.s.j said:
Excuse me, I think internet searching or data gathering without referring to basic concepts cannot solve our problems. Of course this is the disadvantage of today information explosion.
You're right. It wasn't a very good link.
 

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