Which factor affect life of transformer?

Question

Examoogle · Accepted Answer

Option D: All of these

Explanation & Concepts:
The operational life of a transformer is determined by the insulation integrity of its windings and oil. Factors like moisture content, the chemical stability of varnishes, and thermal degradation due to excessive operating temperatures collectively accelerate the aging process (insulation breakdown).

Working Principle: Transformer insulation (cellulose and mineral oil) undergoes chemical degradation known as 'thermal aging'. The Arrhenius Law states that the rate of chemical reaction (and thus degradation) increases exponentially with temperature. Additionally, moisture acts as a catalyst for hydrolysis, reducing the dielectric strength and mechanical durability of the paper insulation.

Key Formulas: $L = A \cdot e^{\frac{B}{	heta + 273}}$ — Representation of insulation life expectancy (Arrhenius equation model where $	heta$ is temperature)

Key Points: Moisture lowers the dielectric strength of transformer oil and induces cellulose hydrolysis.; Varnishes provide mechanical rigidity and protect against atmospheric contaminants.; The '6-degree rule' suggests that for every $6^\circ C$ increase in operating temperature, the life of the insulation is halved.; Periodic DGA (Dissolved Gas Analysis) is used to monitor internal health.

Advantages: Proper monitoring extends the mean time between failures (MTBF).; Effective temperature control optimizes load capacity without premature aging.

Disadvantages: High maintenance costs associated with oil filtration and dehydration.; Complex insulation systems are sensitive to chemical impurities.

Applications: Distribution and Power Transformers; Instrument Transformers (CT/PT)

Additional Info: Moisture contamination is typically measured in parts per million (ppm).. Thermal classes (e.g., Class A, Class B) define the temperature limits for insulating materials.

Answer: D is correct — All listed factors contribute significantly to the chemical and physical degradation of transformer insulation.

Exam Tip: In exams, remember that the 'Rule of 6' (or sometimes 'Rule of 8') is a standard thumb rule for thermal aging of cellulose in electrical machines.

Examoogle · Answer

Option A: Moisture

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Option B: Varnishes

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Option C: Operation temperature

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