Specialist condition monitoring company, WearCheck, is now accredited to perform Dissolved Gas Analysis (DGA) for transformers following a recent assessment by the South African National Accreditation System (SANAS).
The company’s Johannesburg transformer oil testing laboratory now has ISO/IEC 17025 accreditation for testing DGA, moisture, acidity, dielectric strength and polychlorinated biphenyls (PCBs).
Gert Nel, WearCheck’s transformer division manager, outlines the importance of DGA in transformer maintenance: “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.”
WearCheck transformer technicians Kefilwe Ntshabele (SANAS nominated representative and Technical Signatory) and Tumelo Seobi (laboratory supervisor and SANAS Technical Signatory) with the company’s SANAS certiicate for Dissolved Gas Analysis.
Transformers help to transfer electricity over long distances often playing a key role 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 very important. DGA saves transformer operators on avoidable repairs and time and helps avoid greater problems such as an 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 vapour), air ingress (oxygen and nitrogen), partial discharge (hydrogen and carbon monoxide) and sparking and arcing (methane and acetylene). The early detection of potential transformer faults enables remedial action to be implemented, averting major failures.
Case study
Nel give the example of a WearCheck client that had only requested moisture/dielectric/ acidity (M/A/D) results over the years and when the very first DGA was done, a critical error showed up. The DGA indicated an actual internal electrical problem, but the client wasn’t convinced and even did two oil changes in 24 months, hoping this would solve the problem. However, changing the oil did not fix the problem. All it did was remove evidence of the problem. The actual electrical fault was still present in the transformer and a new trend was then required after the oil was changed.
In this case, the DGA was indicative of an actual fault and the oil changes did not fix the fault. This is very important, as many clients only test for (moisture/ dielectric (M/D) 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.
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