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Examoogle • User • info@examoogle.com • EE-2024-8821
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Transformer oil acidity should be
0.4 mg KOH/g
0.5 mg KOH/g
0.6 mg KOH/g
0.7 mg KOH/g
0.4 mg KOH/g
Quick Summary: Transformer oil acidity is a critical metric used to assess the degradation or 'aging' of insulating oil due to oxidation. The acidity level, measured as mg of Potassium Hydroxide (KOH) required to neutralize 1 gram of oil, must not exceed 0.4 mg KOH/g for operational safety.
Transformer oil acidity is a critical metric used to assess the degradation or 'aging' of insulating oil due to oxidation. The acidity level, measured as mg of Potassium Hydroxide (KOH) required to neutralize 1 gram of oil, must not exceed 0.4 mg KOH/g for operational safety.
Acidity=moilmKOH — Represents the Neutralization Number in mg KOH/g
As a transformer operates, the oil is exposed to high temperatures and contact with oxygen, leading to the formation of organic acids, sludge, and water. These acidic by-products accelerate the deterioration of solid paper insulation and promote corrosion of metallic parts. Maintaining acidity below 0.4 mg KOH/g ensures the insulating properties remain within acceptable limits for the long-term reliability of the transformer.
Acidity increases as transformer oil oxidizes over time.
Higher acidity levels reduce the dielectric strength of the insulating system.
Acidic oil accelerates the degradation of cellulose paper insulation.
Periodic testing is required as part of the preventive maintenance schedule (IS 1866).
Prevents internal corrosion of transformer tanks and components.
Extends the lifespan of the solid insulation (cellulose paper).
Provides an early warning indicator for oil replacement or regeneration.
Does not provide information about moisture content directly.
Testing requires laboratory titration, which can be time-consuming.
Routine condition monitoring of Power Transformers.
Acceptance testing for new transformer oil.
Diagnostic analysis for failed or overheated transformers.
According to IS:1866, the maximum permissible acidity for in-service transformer oil is generally 0.4 mg KOH/g. Values exceeding this threshold indicate the oil should be reclaimed or replaced.
Options B, C, and D represent values that indicate higher levels of oil degradation, making them unsuitable as standard limits for healthy insulation.
A is correct — The maximum permissible acidity limit for mineral insulating oil in transformers is typically 0.4 mg KOH/g to prevent corrosion and paper deterioration.
Always remember that transformer oil acts as both an electrical insulator and a cooling medium; its chemical stability is just as important as its dielectric strength.