PMRF- NPTEL- Design of Photovoltaic system

A: Pick the wrong answer and you’re left assuming a fire barrier that doesn’t exist, which risks connector ignition on a live array. The DC isolator only interrupts current when operated and doesn’t extinguish a series arc formed upstream at a high-impedance discontinuity like a loose MC4. That arc is sustained by the array’s Vmp, independent of downstream disconnection, so relying on the isolator avoids neither the plasma nor the heat source.

A: Choose wrong and you’ll chase firmware or grid ghosts while energy yield keeps bleeding. Midday clear-sky dips that self-clear point to thermal hot-spots driving bypass diode conduction, which drags string voltage without any AC disturbance. Grid or firmware issues don’t selectively line up with cell temperature peaks nor recover on a thermal timescale of seconds.

A: Get this wrong and you’ll specify rails that lose cross-section long before the PPA ends, forcing retrofit. In salt-laden air, chlorides break down the passive layer on aluminum, especially at crevices around bolts, making pitting the life-limiting mechanism. SO₂ and UV play secondary roles here, and galvanic couples aren’t the primary driver without aggressive dissimilar metal contact.

A: Assume full de-energization and you expose responders to live DC during roof access. Rapid shutdown limits conductor voltage outside the array, not the module interconnects themselves, which stay energized under sun until contactors or electronics collapse voltage. Grid backfeed is blocked by inverter isolation, and the other hazards don’t match the post-shutdown window.