PG Diploma Solar Semester Two Paper 1 Exam Section B

Short Answer Questions (181–220)

181. Explain BOS in a solar PV system.
Model Answer: Balance of System includes all parts of the solar PV system except the modules themselves. It includes mounting structures, junction boxes, combiner boxes, inverters, electrical protection devices, grounding, lightning protection, and monitoring systems. These components support installation, safety, power collection, conversion, distribution, and performance monitoring.
Marks: 6

182. Write a short note on module mounting structures.
Model Answer: Module mounting structures support the solar modules at the required tilt and orientation and transfer wind and dead loads to the roof or supporting surface. Common materials include hot dip galvanized iron, aluminium, and mild steel. Components include C-sections, purlins, rails, tilt brackets, cable trays, and nuts and bolts.
Marks: 6

183. Describe the constructional components of a module mounting structure.
Model Answer: The structure includes a vertical post or C-section, purlin or horizontal rail, tilt bracket, mounting brackets, cable tray, and nuts and bolts. These components together provide stable support, required inclination, and secure fastening for the modules.
Marks: 6

184. Explain the purpose and features of a PV module junction box.
Model Answer: A junction box is an enclosure attached to the back of the module where electrical connections are made. It is usually fixed using silicon adhesive. A good junction box is watertight, often IP 67 rated, and contains important elements like diodes. It protects the electrical connections from the environment.
Marks: 6

185. Discuss the functions of a string combiner box.
Model Answer: A string combiner box combines the output of multiple PV strings. It provides surge protection, overcurrent protection, safe connection of strings, and may include monitoring and communication functions. It also uses fuse holders, SPDs, disconnects, and terminal connectors for safe operation.
Marks: 6

186. Write a note on AC combiner box and its components.
Model Answer: An AC combiner box is used to combine AC outputs from multiple string inverters before sending them to the main distribution or switchboard. Components include the enclosure, MCCB, AC fuse, SPD, AC busbar, load break switch, and power monitoring devices. It supports safe AC power management and protection.
Marks: 6

187. Explain the role of MCB and MCCB in solar PV systems.
Model Answer: MCB protects AC or DC circuits from overload and short circuit, especially at lower current ratings. MCCB is used for higher current circuits and provides more robust protection and switching capability. Both improve safety, prevent damage to equipment, and support isolation during faults.
Marks: 6

188. What is the importance of grounding in solar plants?
Model Answer: Grounding provides a safe path for fault current and reduces the risk of electric shock, equipment damage, and surge effects. In solar plants, earth pits are used to maintain low resistance, generally below 5 ohms. Proper grounding improves safety, system reliability, and lightning protection effectiveness.
Marks: 6

189. Write a short note on lightning arrestors in solar systems.
Model Answer: Lightning arrestors protect the plant against high-voltage surges caused by lightning. The notes mention Early Streamer Emission type protection. Lightning protection is necessary because solar installations are exposed outdoor structures and can be damaged by direct or induced lightning events.
Marks: 6

190. Explain the need for energy monitoring systems.
Model Answer: Energy monitoring systems measure and analyze power generation and system performance. They help identify faults, track efficiency, compare actual production with expected production, and support better maintenance planning. These systems improve system reliability and operational decisions.
Marks: 6

191. Differentiate between PV wire, USE-2 wire, and THHN wire.
Model Answer: PV wire is commonly used in PV systems and generally has XLPE insulation with good UV, moisture, and ozone resistance. USE-2 wire is underground service entrance wire and also uses XLPE insulation. THHN is thermoplastic high heat-resistant nylon-coated wire and typically uses PVC insulation. Their temperature ratings and applications differ.
Marks: 6

192. Explain the difference between AC and DC solar cables.
Model Answer: DC cables are used from modules to inverter-side DC circuits because PV modules produce DC electricity. AC cables are used after inversion to connect to panels, transformers, and the grid. DC cable transmission has lower loss according to the notes, while AC cables require different insulation and conductor arrangements to manage alternating current.
Marks: 6

193. Discuss the importance of correct cable sizing.
Model Answer: Correct cable sizing is essential to avoid overheating, reduce power loss, and keep voltage drop within acceptable limits. Undersized cables can create fire hazards and reduce efficiency. Proper cable size must be chosen considering maximum current, voltage drop, cable length, ambient temperature, grouping, and installation conditions.
Marks: 6

194. List and explain the factors affecting cable size selection.
Model Answer: Key factors are maximum current, acceptable voltage drop, grouping factor, ambient temperature, conduit condition, and distance from the solar panel to the load. Longer cable runs increase resistance and voltage drop. Grouping and high ambient temperature reduce current carrying capacity and require derating.
Marks: 6

195. Write a short note on derating factors in solar cable selection.
Model Answer: Derating factors correct the rated current carrying capacity of a cable for real operating conditions. Important derating factors include ambient temperature, conduit pipe effect, and grouping factor. The derated current carrying capacity must be greater than the maximum current, otherwise a higher cable size must be selected.
Marks: 6

196. Explain voltage drop in solar cables and why it matters.
Model Answer: Voltage drop is the reduction in voltage as current flows through a cable. It matters because excessive voltage drop causes power loss and improper equipment operation. The notes mention 2% voltage drop on the DC side and 1% on the AC side as accepted values in solar PV systems.
Marks: 6

197. Describe important solar cable installation best practices.
Model Answer: Best practices include avoiding cable curves, protecting cables near metal edges, using proper fastening clips for perforations, and using edge clips to avoid drilling panels. Good cable management also requires safe routing, accessories, regular testing, and protection from environmental and human damage.
Marks: 6

198. Write a note on loose connections in solar cable systems.
Model Answer: Loose connections happen when the mechanical connection between wire and terminal is not secure. Causes include natural degradation, vibration, temperature fluctuation, and poor installation. Signs include discoloration, melting, burning smell, and high temperature visible on an infrared thermal camera.
Marks: 6

199. Explain the causes and effects of cable corrosion.
Model Answer: Cable corrosion occurs due to prolonged outdoor exposure, chemicals, saltwater, or certain soil conditions. It increases electrical resistance, generates heat, reduces performance, shortens cable life, and can create safety hazards like short circuits or fire. Rust or discoloration on connectors is a common sign.
Marks: 6

200. Write a note on cable overheating.
Model Answer: Cable overheating is caused by loose connections, damaged insulation, and excessive current. It leads to energy loss, lower system performance, and a higher risk of failure or fire. Signs include hot cables, discoloration, and melted insulation or connectors.
Marks: 6

201. Explain why pre-installation preparation is important in solar projects.
Model Answer: Pre-installation preparation is essential for optimizing system performance, safety, compliance, equipment compatibility, cost efficiency, durability, and understanding maintenance needs. Good preparation reduces future problems and helps ensure efficient installation.
Marks: 6

202. Describe site readiness for PV installation.
Model Answer: Site readiness includes site assessment, structural integrity, shading analysis, roof condition for rooftop projects, and electrical infrastructure. These checks help ensure that the site can safely and effectively support the PV system.
Marks: 6

203. Write a short note on tools required by a solar field crew.
Model Answer: The notes list solar panel hanger, battery-operated drill, PV tester, fall protection, and cable and connector tools. These tools help in safe lifting, mounting, testing, and making proper electrical connections during solar installation.
Marks: 6

204. Explain the main steps involved in installing solar panels.
Model Answer: Major steps include site preparation, mount installation, panel installation, electrical wiring connection, connecting the system with the inverter, and finally connecting the inverter to grid or battery. The process must be carried out carefully and sequentially for safety and performance.
Marks: 6

205. Describe roof mounting of solar panels.
Model Answer: Roof mounting involves locating and marking roof rafters, installing roof attachments, installing racking rails, lifting the panels onto the roof, and mounting the panels on the rails. This method is common for rooftop solar plants and requires attention to structural safety and water flow.
Marks: 6

206. Describe ground mounting of solar panels.
Model Answer: Ground mounting involves building a foundation, installing the racking railing, and mounting the panels on the rails. It is suitable where enough land is available and offers easier access for maintenance compared to some rooftop systems.
Marks: 6

207. Explain the importance of orientation and inclination in PV systems.
Model Answer: Proper orientation and inclination increase solar energy capture. The notes state that maximum energy is produced when sunlight strikes the module close to 90°. A panel slope of 30–40° is considered suitable, and in the northern hemisphere modules should generally face south.
Marks: 6

208. Write the grid-tie electrical connection path.
Model Answer: In a grid-tie system, PV strings connect to a junction box, the junction box connects to inverter(s), and the AC output goes to the main or sub-panel. This path ensures that generated electricity is converted and delivered for grid-connected use.
Marks: 6

209. Explain the off-grid wiring path.
Model Answer: In an off-grid system, PV strings connect to the combiner box, the combiner box connects to the charge controller, the charge controller connects to the battery bank, the battery bank connects to the inverter, and the inverter feeds the load panel.
Marks: 6

210. Write a short note on inverter installation.
Model Answer: Inverter installation includes selecting the location, turning off power sources, mounting the inverter, making DC and AC electrical connections, grounding, checking, testing, and arranging monitoring and maintenance. Grid-tie inverters may be mounted indoors, outdoors, or on a substructure, while off-grid inverters are wall-mounted indoors.
Marks: 6

211. Explain racking system installation and its considerations.
Model Answer: Racking systems mount solar panels on roofs, ground, or poles to access sunlight effectively. Important considerations include grounding/bonding and mechanical loading. Structural integrity and alignment are critical for long-term stability, safety, and performance of the solar array.
Marks: 6

212. Write a note on wiring practices in electrical component installation.
Model Answer: Appropriate wiring must be selected according to application and load requirement. Wiring should be correctly sized to avoid overheating. Color codes should be followed, and the wiring should be secured with clamps, staples, or ties, while kept away from sharp edges, heat sources, and moving parts.
Marks: 6

213. Explain the role of junction boxes and disconnects in installation.
Model Answer: Junction boxes are installed at strategic locations where electrical connections or splits are needed, and they must be sealed properly. Disconnect switches are installed to isolate components for maintenance or emergency conditions, improving safety during operation and servicing.
Marks: 6

214. Why is wire management important in solar installations?
Model Answer: Proper wire management keeps the installation neat and organized, reduces tangling, prevents interference with other systems, and protects wires from damage. Cable trays, conduits, and raceways help route wires safely and improve system reliability and maintenance convenience.
Marks: 6

215. Explain the importance of quality control in PV installation.
Model Answer: Quality control ensures proper positioning and connection of PV components, increases system efficiency, improves longevity, and ensures compliance with standards. It reduces the chance of premature failure and helps maintain legal and technical acceptability.
Marks: 6

216. Write a short note on inspections and testing procedures.
Model Answer: Inspections and testing include pre-installation site and equipment inspection, during-installation component verification and wiring inspection, and post-installation testing such as electrical testing, grounding check, and insulation resistance testing. Functional testing and inverter checks are also part of commissioning.
Marks: 6

217. Explain safety measures during solar panel installation.
Model Answer: Safety measures include correct ladder use, avoiding installation in windy or rainy conditions, keeping the roof clear of tools, not walking backward on the roof, lifting panels carefully, avoiding electrical hazards, and wearing appropriate clothing and protective equipment.
Marks: 6

218. Define feasibility study and list its main elements.
Model Answer: A feasibility study determines whether a solar PV project is technically and financially suitable. Main elements include available area, transmission availability, solar resource, ground conditions, economic analysis, environmental and regulatory considerations, and community acceptance.
Marks: 6

219. Explain key site selection criteria for solar projects.
Model Answer: Key site selection criteria include solar resource potential, land availability and characteristics, climate, grid connection, environmental impact, regulatory considerations, transport access, security, community factors, land ownership, economic viability, and site conditions for construction.
Marks: 6

220. Write a note on regulatory compliance in solar projects.
Model Answer: Regulatory compliance includes national and state requirements such as National Solar Mission policies, PPAs, net metering, renewable purchase obligations, grid connectivity, land use permission, environmental clearances, safety codes, and financial incentives. Compliance ensures legal approval and proper project execution.
Marks: 6