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As a transformer ages, gases and liquid contaminants can dissolve in its fluid and lead to transformer failure. Sampling and analysis of the fluid form the cornerstone of transformer preventive maintenance.
DYMAX and transformer manufacturers recommend a regular transformer fluid analysis routine. Such testing provides reference points that make possible the development of a historical trend in transformer fluid condition. Quantitative analysis of impurities can indicate the priority of taking action while the transformer is under study.
The insulating fluid in a power transformer performs two major functions:
- Serves as electrical insulation to withstand the high voltages inside the transformer; and
- Acts as a heat transfer medium to reduce heat build-up generated within the transformer windings.
 Fluid must maintain good electrical properties while resisting thermal degradation and oxidation. Deterioration occurs when water enters the fluid from an outside source or when paper insulation disintegrates into gaseous products, acids and particulate matter. Even small particulates can affect color and clarity.
DYMAX uses several tests to measure the quality of insulating fluid and to establish benchmarks for its life and degree of deterioration. While your transformer operates in normal service, DYMAX can draw samples of the insulating fluid through drain valves or sampling ports. No single test is a basis for condemning fluid. DYMAX considers the whole picture.
DYMAX technicians can travel to your site and draw fluid samples, or we can furnish you the proper equipment to take your own samples that you can send to us for analysis.
When these tests suggest that the fluid should be processed, DYMAX can come to your transformer and remove these impurities, thus returning the fluid to a like-new condition and eliminating the deteriorating effects of gas, acids and water on the insulation system.
If and when a problem is evident, DYMAX can address it by offering a complete line of services, including:
- Electrical testing
- Component replacement
- LTC repair
- Transformer repair
- Internal inspection
- Hot oil services
 DYMAX case studies of Dissolved Gas Analysis (DGA) and Transformer failures.
Customer A
5000 KVA GE transformer. An oil sample taken on 3/3/00 indicated bad DGA. Total combustible gases were 35,196. Individual gases exceeding threshold limits were: hydrogen at 3102 ppm, methane at 11,940 ppm, ethane at 4336 ppm, ethylene at 14,869 ppm, acetylene at 15 ppm. This critical transformer failed on 4/25/00. The customer had to deal with this situation on an emergency basis.
Customer B
2500 KVA RTE/Cooper transformer. An oil sample taken on 3/3/00 indicated bad DGA. Total combustible gases were 1809. Individual gases exceeding threshold limits were: methane at 321 ppm, ethane at 120 ppm, ethylene at 741 ppm, acetylene at 5 ppm. This critical transformer failed on 5/21/00. The customer had to deal with this situation on an emergency basis.
Customer C
2500 KVA RTE/Cooper transformer. An oil sample taken on 9/2/99 indicated bad DGA. Total combustible gases were 31,681. Individual gases exceeding threshold limits were: hydrogen at 1205 ppm, methane at 7539 ppm, ethane at 3231 ppm, ethylene at 19,297 ppm, acetylene at 114 ppm. This critical transformer failed on 9/20/99. The customer had to deal with this situation on an emergency basis.
It should be noted that when this same transformer was sampled one year earlier on 9/2/98, the DGA tests were well within normal limits. Total combustible gases were 29. Non-detectable levels were recorded for hydrogen, methane, ethane and acetylene. Ethylene was at 3 ppm.
Click here for example reports.
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