Detection of inter-turn winding-short fault in 1-phase transformer

In summary, the no-load current in a single-phase transformer with inter-turn winding short-circuit fault has an increasing fundamental component and unchanged higher harmonics. This leads to a decrease in the Total Harmonic Distortion (THD) of the no-load current under fault, with the THD decreasing even further as the level of fault increases. This may be due to the iron core of the transformer having less effective permeability at higher frequencies, causing the leakage reactance to become a larger proportion of the total reactance. However, this cannot fully explain the trend and further research on the properties of the iron core at harmonic frequencies is needed.
  • #1
Shantanav
9
0
Hi all,

I have simulated (both in software and experimentally) inter-turn winding short-circuit fault in a single-phase transformer (working as a stand alone unit). I have the following observation but don't know the reason behind it:-

The fundamental component in the no-load current is increasing under fault, but all other harmonics (3rd, 5th. 7th etc) remain almost unchanged. So, under fault the Total Harmonic Distortion (THD) of the no-load current is improving i.e. decreasing.

Higher is the level of fault (i.e. number of turns shorted), lower is the no-load current THD.

Any ideas, why this trend is happening ?

Cheers,
Shanto
 
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  • #2
My guess:
Leakage reactance at nth harmonic is nX its line frequency number of ohms. So harmonic currents see more ohms of series reactance than does fundamental current.

What are properties of the iron core at harmonic frequencies?
Try some searches on "complex permeability".
Above some frequency well into audio range the iron no longer has any effective permeability .

http://www.diva-portal.org/smash/get/diva2:125733/FULLTEXT01.pdf

So as frequency goes up, leakage reactance becomes increasingly larger proportion of total because the core acts less and less like textbook iron..

That can't be the whole answer, but hopefully is food for thought.
 
Last edited by a moderator:

1. How is an inter-turn winding-short fault in a 1-phase transformer detected?

An inter-turn winding-short fault in a 1-phase transformer can be detected using various methods such as visual inspection, transformer ratio test, and winding resistance test. However, the most common method is the transformer turns ratio test, which involves injecting a voltage to the healthy winding and measuring the resulting voltage in the faulty winding.

2. What causes inter-turn winding-short faults in 1-phase transformers?

Inter-turn winding-short faults in 1-phase transformers can be caused by various factors such as mechanical stress, aging of insulation materials, and thermal overloading. These faults can also occur due to manufacturing defects or poor maintenance practices.

3. How does an inter-turn winding-short fault affect the performance of a 1-phase transformer?

An inter-turn winding-short fault can significantly impact the performance of a 1-phase transformer. It can lead to a decrease in the transformer's efficiency, increase in power loss, and distortion of the output voltage. In severe cases, it can also cause the transformer to overheat and fail.

4. Can inter-turn winding-short faults be repaired in 1-phase transformers?

In most cases, inter-turn winding-short faults in 1-phase transformers cannot be repaired. The fault usually occurs due to insulation breakdown, which cannot be fixed. The only solution is to replace the faulty transformer with a new one.

5. How can inter-turn winding-short faults in 1-phase transformers be prevented?

Inter-turn winding-short faults in 1-phase transformers can be prevented by regular maintenance and testing. This includes visual inspections, ratio tests, and insulation resistance tests. It is also essential to operate the transformer within its rated limits and avoid overloading it to prevent thermal stress on the windings.

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