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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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Which methods of purifying insulating oil?
Filter press
Chemical test
Earth media test
All of above
Filter press
Quick Summary: The filter press is a standard industrial device used to remove solid impurities, moisture, and sludge from transformer insulating oil. It forces oil through layers of specialized filter paper that trap contaminants, thereby improving the dielectric strength of the oil.
The filter press is a standard industrial device used to remove solid impurities, moisture, and sludge from transformer insulating oil. It forces oil through layers of specialized filter paper that trap contaminants, thereby improving the dielectric strength of the oil.
Vbd∝m1 — where Vbd is the breakdown voltage and m is the moisture content in ppm.
The principle relies on mechanical separation and moisture absorption. Insulating oil is passed through a series of filter plates stacked with cellulose-based filter papers; the paper allows the oil to pass while trapping sludge and particles, and also adsorbs dissolved moisture due to its hygroscopic nature.
Transformer oil must be periodically purified to maintain high dielectric strength and heat dissipation properties.
Filter press is effective for mechanical impurities, but for very high moisture, centrifuging or vacuum dehydration is preferred.
The oil's dielectric strength is significantly reduced by the presence of cellulose fibers and moisture.
Simple operation and maintenance.
Effectively removes suspended solid particles and fibers.
Relatively low cost compared to vacuum purification systems.
Not highly effective for dissolved gases.
Slower process for large volumes of oil compared to vacuum dehydration.
Filter papers require frequent replacement.
Distribution transformers
On-site maintenance of power transformers
Purification of lubrication and hydraulic oils
Option B (Chemical test) and C (Earth media test) are diagnostic evaluation methods, not purification processes.
Standard dielectric strength requirement for transformer oil is typically >30 kV for a 2.5 mm gap.
A is correct — Filter press is a mechanical purification method used to remove solid impurities and moisture from insulating oil.
Always distinguish between diagnostic tests (like BDV test, Acidity test, IFT) and physical treatment methods (like Filter press, Centrifuging, Vacuum dehydration).