HV Exit Exam • Set 7 Question 22 of 30

Submerging circuit breaker contacts in dielectric transformer oil is an effective method of:

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Direct Answer

Option A: Arc cooling, gas generation (hydrogen blast), and rapid deionization

In oil circuit breakers, the intense arc decomposes oil into hydrogen gas (70%) and hydrocarbon vapors, creating a high-pressure bubble that violently cools and deionizes the arc path at current zero.

All Options

Arc cooling, gas generation (hydrogen blast), and rapid deionization (Correct Answer)

Complete arc prevention

Electromagnetic induction shielding only

Radio frequency amplification

Detailed Explanation & Context

Relevant Framework: STCW 2010 Manila Amendments • DG Shipping E-Learning & Exit Exam Standards • High Voltage Safety Officer & Switchgear Operations (HV).

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Q1 High Rupturing Capacity (HRC) fuses provide the most effective and rapid protection under conditions of: Q2 For high-speed motor circuit breakers, the total closing time from command signal to contact touch is typically in the order of: Q3 Which type of protective relay is commonly used to protect electric motors against continuous moderate overload? Q4 According to Preece's Law, the fusing current (I) of a fuse wire is related to its wire diameter (D) by the relationship: Q5 In a circuit breaker contact gap, ionization of the medium is NOT facilitated by: Q6 An ideal fuse wire material should possess which combination of physical properties? Q7 For extra-high-voltage (EHV) transmission networks above 220 kV, which circuit breaker type is predominantly selected? Q8 The number of power-frequency AC cycles in which a modern high-speed circuit breaker completes its tripping and arc clearing operation is: Q9 Which of the following metals is best suited for manufacturing precision HRC fuse elements due to its resistance to oxidation and low specific resistance? Q10 In a circuit breaker, the current that is flowing through the contacts at the precise instant of contact separation is known as the: