आधारभूत विद्युत् (Basic Electrical) – Basic Electrical Engineering MCQ
आधारभूत विद्युत् (Basic Electrical) – इलेक्ट्रिकल र टेलिकम
Basic Electrical Engineering · Technical – Electrical, Mechanical & Telecom · २,२९९ प्रश्न
२,२९९ प्रश्न उपलब्ध। मोड छान्नुहोस्:
आधारभूत विद्युत् (Basic Electrical): प्रश्न र उत्तर
सही लागेको विकल्पमा थिच्नुहोस्। सही भए हरियो, गलत भए रातो देखिन्छ; ३ सेकेन्डपछि सही उत्तर र व्याख्या देखिन्छ।
सही: ० / ०
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For medium-voltage (about 11–33 kV) distribution switchgear, the circuit breakers now most widely used are:
सही उत्तर: ग) vacuum circuit breakers
Vacuum interrupters need little maintenance and have excellent arc-quenching at medium voltages; SF₆ dominates at higher transmission voltages.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Differential protection of a transformer or generator operates on the principle of:
सही उत्तर: घ) comparing the currents entering and leaving the protected zone
Under normal conditions or external faults the two currents balance; an internal fault upsets the balance and operates the relay.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An overcurrent relay is set at 100% of its 5 A rating and fed from a 400/5 A CT. For a fault current of 4000 A, the plug setting multiplier (PSM) is:
सही उत्तर: ख) 10
Relay current = 4000 × 5/400 = 50 A; PSM = 50/(1.0 × 5) = 10.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Series reactors (current-limiting reactors) are installed in power systems mainly to:
सही उत्तर: क) limit the short-circuit current
Their reactance adds to the fault path, limiting fault current to a level the breakers can interrupt.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In power systems, the most frequently occurring type of fault is:
सही उत्तर: ग) the single line-to-ground fault
About 70–80% of faults on overhead lines are single line-to-ground (e.g. flashover of one insulator); symmetrical three-phase faults are the rarest.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A generator reactance is 0.1 pu on its own 10 MVA rating. On a 50 MVA base at the same voltage, its per-unit reactance is:
सही उत्तर: ख) 0.5 pu
Z_new = Z_old × (MVA_new/MVA_old) × (kV_old/kV_new)² = 0.1 × 50/10 = 0.5 pu.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 10 MVA transformer has a reactance of 10% (0.1 pu). Ignoring source impedance, the fault level for a three-phase fault at its terminals is:
सही उत्तर: क) 100 MVA
Short-circuit MVA = base MVA/Z_pu = 10/0.1 = 100 MVA.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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On a base of 10 MVA and 11 kV, an impedance of 6.05 Ω expressed in per unit is:
सही उत्तर: ख) 0.5 pu
Base impedance = kV²/MVA = 121/10 = 12.1 Ω, so Z_pu = 6.05/12.1 = 0.5.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An arc suppression coil (Petersen coil) connected between the neutral and earth is used in:
सही उत्तर: ग) resonant earthing of the neutral
The coil's inductance is tuned to the line's capacitance to earth, so the capacitive earth-fault current is neutralised and arcing faults self-extinguish.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 'wave trap' (line trap) installed at a substation on a transmission line is used for:
सही उत्तर: क) power line carrier communication (blocking high-frequency carrier signals from entering the station)
The wave trap is a parallel-tuned circuit offering high impedance to the carrier frequency while passing 50 Hz power current.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
यी अभ्यास प्रश्न हुन्, आधिकारिक प्रश्न होइनन्। पाठ्यक्रम, विज्ञापन र नतिजाका लागि सम्बन्धित निकायको आधिकारिक वेबसाइट हेर्नुहोस्। उत्तरमा गल्ती भेटे प्रश्नमुनिको "टिप्पणी / गल्ती रिपोर्ट" मा लेख्नुहोस्।
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