Specialist condition monitoring company, WearCheck, is now accredited to perform DGA, or Dissolved Gas Analysis, for transformers, following a recent assessment by SANAS – the South African National Accreditation System.
The company’s Johannesburg transformer oil testing laboratory now has ISO/IEC 17025 accreditation for testing DGA, moisture, acidity, dielectric strength, and PCBs (polychlorinated biphenyls) in transformer oils.
Gert Nel, WearCheck’s transformer division manager, outlines the importance of DGA in the maintenance of transformers. “Dissolved gas analysis is used mostly for fault detection in transformers, and it is critically important that the analysis is accurate. By analysing the gases dissolved in the transformer’s oil, we gain important clues about the health of the transformer.
“WearCheck is pioneering the way in transformer maintenance in Southern Africa, and this SANAS accreditation is a powerful attribute for our laboratories.”
Transformers help to transfer electricity over long distances, often playing key roles in the infrastructure of a region and ensuring power supply to cities, industrial plants and other critical users. Therefore, early detection of faults and potential failures is important.
DGA saves transformer operators money on avoidable repairs and time and helps prevent greater problems such as interrupted power supply. It also helps prolong the life of the transformer.
Nel explains the process: “Small amounts of gases are formed in the oil when a transformer is in operation. Using DGA, hidden problems inside the transformer are revealed by detecting the gases in the oil.
“Some of the common transformer problems and the associated gases include oil overheating (ethane and ethylene), insulation paper overheating (carbon monoxide, carbon dioxide, and acetic acid gases), air ingress (oxygen and nitrogen), and partial discharge (hydrogen gas and carbon monoxide gases), sparking and arcing type of faults (methane and acetylene).
“The early detection of potential transformer faults enables remedial action to be implemented, and major failures averted. “
Case study
Nel shares the case of a WearCheck client that had requested only M/A/D (moisture / acidity /dielectric) results over the years, and when the first DGA was done, it showed a critical error.
“The DGA indicated an internal electrical problem, but the client was not convinced and did two oil changes within 24 months, hoping this would solve the problem. However, changing the oil did not fix the problem; what it did was it removed evidence of the problem. The electrical fault was still present in the transformer, and a and a new trend was then required after the oil had been changed.
“In this case, the DGA indicated a fault, and the oil changes did not fix the fault. This is important, as a lot of clients only test for M/D (moisture / dielectric), and not the full DGA analysis. Eventually, the client made the decision to include all tests in its ongoing maintenance plan and took the recommended remedial action to fix the electrical fault.”
The picture shows WearCheck transformer technicians Kefilwe Ntshabele, SANAS nominated representative and Technical Signatory, and Tumelo Seobi, Laboratory Supervisor and SANAS Technical Signatory, with the accreditation certificates the laboratory holds.
For more information visit: www.wearcheck.co.za
