36 Bannick Court
Canning Vale WA, 6155

M7 11/3.3 KV Tap changer repairs

GTS was recently tasked with a thorough examination and repair of a tap changer for one of our valued clients. The project involved the testing and maintenance of a high-voltage transformer, and here's what we uncovered:

Transformer Testing Highlights: • Oil samples were taken from the main tank after the tap changer oil had been drained. The results indicated no signs of corrosive sulfur, ensuring the transformer’s longevity.

M7 11/3.3 KV Tap changer repairs 
It was noted that compressor 4 frequent starting (up to 29 times in 5 hours 40 minutes) caused more tap changes than normal

 Number of operations:
• 2022 operations count – 44601
• 2024 operations count – 47085
o Only 2484 (allowable between service intervals 70 000) operations done in 2 years, since last (since it is a delta tap changer, we do 2 yearly maintenance, within the MR inspection interval).

This amounts to only 2,484 operations over two years, well within the allowable limit of 70,000 operations between service intervals.
However, our inspection revealed an abnormality: Compressor 4 was frequently starting, recording 29 starts in just 5 hours and 40 minutes, which contributed to more tap changes than normal. This highlights the importance of close monitoring to prevent premature wear and ensure reliable performance between maintenance cycles.

Conclusion: Thanks to the rigorous testing and diagnostic process, GTS was able to provide essential maintenance, ensuring the transformer continues to operate efficiently and reliably.

 

M7 11/3.3 KV Tap changer repairs for a GTS client

Test results back for transformer.
  • Oil sample taken form main tank, tap changer oil already drained.
Test results negative for corrosive Sulphur.
  • DIN 51353 (Silver Sulphide test) - Absent
  • IEC-62697 DBDS - 8 ppm (value very low)
  • ASTM D1275B – 3B (non-corrosive)
  • IEC 62535 -3a (non-corrosive)

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