Punjab PSEB Sr. Sec. NSQF Electronics (Solar Panel Installation Technician) cheat sheet

Standard Test Conditions (STC): irradiance 1000 W/m², cell temperature 25 °C, AM 1.5 spectrum; nameplate ratings refer to STC.

Air mass AM 1.5 is the path length of sunlight through the atmosphere at a zenith angle of 48.2°; used as the reference spectrum.

Photovoltaic effect: photons with energy above the band gap create electron-hole pairs in a semiconductor, separated by the junction field to give current.

Cell/module/array hierarchy: a cell gives about 0.5-0.6 V open-circuit; a module series-connects 60 or 72 cells; an array parallels modules or strings.

I-V curve key points: Isc (short-circuit current), Voc (open-circuit voltage), Pmax at the knee, Impp and Vmpp; fill factor FF = (Impp × Vmpp) / (Isc × Voc).

Irradiance change shifts current roughly linearly; cell temperature rise reduces voltage (about -0.3 to -0.45 %/°C for Voc) and slightly raises current.

Module efficiency η = Pmax / (module area × 1000 W/m²) at STC; a 550 W module of 2.58 m² area is about 21.3 % efficient.

Energy yield estimate: E (kWh) = array kWp × peak sun hours × performance ratio; typical performance ratio 0.70-0.85 for Indian conditions.

Series connection adds voltages at the same current; parallel connection adds currents at the same voltage; mismatch in either reduces string output.

Monocrystalline (c-Si): single crystal, black uniform look, efficiency typically 18-23 %, best power per area, higher cost per wafer.

Polycrystalline (multi c-Si): cast ingot with visible grain boundaries, bluish appearance, efficiency typically 15-18 %, lower cost.

Thin film: CdTe, CIGS, amorphous silicon (a-Si); lower efficiency (6-13 %) but flexible, lightweight, better low-light and high-temperature behaviour.

Module construction stack: front glass, encapsulant (EVA), solar cells with busbars and ribbons, back encapsulant, backsheet or rear glass, aluminium frame, junction box with bypass diodes.

Bypass diodes limit hot-spot heating and allow current to bypass a shaded cell group, typically one diode per 20-24 cells.

Datasheet parameters to read: Pmax, Voc, Isc, Vmpp, Impp, temperature coefficients, NOCT, system voltage (1000/1500 V), maximum series fuse rating.

Common defects: micro-cracks (often from handling), PID (potential-induced degradation), snail trails, delamination, browning/EVA discolouration, hot spots, cracked glass, junction-box burn.

IEC 61215 covers design qualification and type approval; IEC 61730 covers safety qualification of modules.

Negative tolerance on nameplate power is a quality signal; flash-test report with measured Pmax should match or exceed the label.

Load assessment: list each appliance, its wattage, hours per day, and quantity; daily energy Wh = Σ (W × h × qty); apply a diversity factor for realistic demand.

Array sizing off-grid: array kWp = daily energy demand (kWh) / (peak sun hours × performance ratio × battery/system losses).

Battery sizing: capacity Ah = (daily kWh × autonomy days) / (battery voltage × depth of discharge × inverter/charge-controller efficiency).

Tilt rule of thumb for fixed mounts in Punjab: latitude ≈ 30-31°, use latitude minus 10-15° for higher summer yield, latitude plus 10-15° for winter-dominant loads.

Orientation: true south in the northern hemisphere; deviations beyond about 15-20° from south reduce annual yield noticeably.

Shading: avoid shadows between 9:00 and 15:00; use a solar pathfinder or shading analysis app; even partial shading of a string causes disproportionate loss.

Row spacing: avoid inter-row shading using height/spacing ratio; spacing ≈ module height × (cos azimuth factor) with a shadow-length calculation for 21 December.

Cable sizing: current-carrying capacity ≥ 1.25 × Isc, and voltage drop ≤ 3 % on DC and ≤ 5 % total AC+DC; Vdrop = 2 × L × I × ρ / A for a two-wire run.

Inverter sizing: DC array kWp typically 1.1-1.3 × inverter AC rating for grid-tied; check DC input voltage window and maximum input current per MPPT.

Roof-mount types: flush/penetrating (rafter-anchored with flashing), ballasted (no penetration, needs weight and wind checks), and elevated/stand-off for shade or access.

Ground-mount: concrete or rammed-pile foundations; structure galvanised (hot-dip) steel or anodised aluminium for corrosion resistance.

Clamps: mid-clamps join adjacent modules, end-clamps secure the outer edges; torque to manufacturer specification (commonly 16-20 N·m) with a calibrated torque wrench.

Rails and purlins must be sized for dead load (modules + structure), live load, snow load where applicable, and wind uplift; check manufacturer load ratings (e.g., 2400 Pa downforce, 2400-5400 Pa uplift).

Wind load basics: design wind pressure p = 0.6 × Vz² (N/m²) using basic wind speed and terrain/exposure factors; edge and corner zones see higher uplift.

Module handling: carry in vertical orientation with two persons, never stand on glass, do not drop or place tools on modules, store on edge on padded surface.

Keep roof waterproofing intact: use proper flashing and sealant on penetrations; inspect after installation.

Mechanical clearances: minimum 100 mm gap between module and roof for ventilation; avoid contact between dissimilar metals to prevent galvanic corrosion.

DC cabling: use solar-rated (PV1-F/H1Z2Z2-K) double-insulated, UV-resistant, flexible cable; size for 1.25 × Isc continuous current and ≤ 3 % voltage drop.

MC4 connectors: only mate same-brand/same-type connectors, crimp with the correct tool, check polarity before plugging, and never disconnect under load.

String wiring: series strings to combiner box; each string fused at ≤ maximum series fuse rating of the module; use string fuses or DC breakers.

Combiner box: aggregates strings, houses fuses, DC isolator, and often surge protective devices; label string numbers and polarity clearly.

Earthing: bond module frames, mounting structure, inverter enclosure and DC/AC enclosures to a common earth electrode; earth continuity resistance typically < 1 Ω.

Lightning and surge protection: use Type 2 DC SPD on the DC side and Type 2 AC SPD on the AC side; equipotential bonding of the array.

Cable routing: separate DC and AC cables, avoid loops, use UV-rated cable trays/conduit, support cables at regular intervals, and avoid sharp bends below the cable's minimum bend radius.

Polarity and continuity checks before energising: verify Voc per string, confirm no reverse polarity, and confirm insulation resistance (typically ≥ 1 MΩ at 1000 V test voltage).

Grid-tied inverter: synchronises with the grid, no battery, anti-islanding protection per IEC 62116/local rules; requires grid-tie approval and net metering.

Off-grid inverter: standalone, must match battery bank DC voltage and load surge requirements; often includes a charger.

Hybrid inverter: grid-tied plus battery backup; supports self-consumption, backup and export modes; check MPPT count and battery compatibility.

PWM charge controller: simple, cheap, forces panel voltage near battery voltage, lower efficiency; suitable for small systems with matched panel voltage.

MPPT charge controller: tracks maximum power point, typically 93-98 % efficient; size by array Voc (cold) below controller max PV input and array Isc below max input current.

Battery types: lead-acid flooded, VRLA/AGM/GEL, and lithium-ion (LFP); LFP offers higher depth of discharge (80-90 %) and longer cycle life than lead-acid (50 % DoD).

Meters and monitoring: DC/AC energy meters, generation meter for net metering, and monitoring via inverter app or SCADA; log daily kWh, PR and fault codes.

Balance of system also includes DC/AC isolators, fuses, combiner box, SPDs, and the AC distribution board with RCCB/MCB protection.

Multimeter: measure Voc per string, polarity, and DC voltage at the inverter input; compare with expected temperature-corrected values.

Clamp meter: measure DC current per string under load to detect mismatch or a dead string; compare with irradiance-corrected Isc.

Insulation tester (megger): measure insulation resistance of DC cabling to earth at 500-1000 V; a low reading indicates cable damage or moisture ingress.

Continuity test: verify earth bonding and cable continuity with the circuit de-energised; resistance should be near zero for a good bond.

Open-circuit voltage check: string Voc should be sum of module Voc adjusted for cell temperature; a low reading indicates a faulty module or open connection.

Short-circuit current check: compare with irradiance-corrected Isc; a low reading indicates shading, soiling, or a faulty module.

Commissioning: verify polarity, insulation resistance, earth continuity, inverter start-up, anti-islanding test, and record all values in a commissioning sheet.

Fault finding: low output often from soiling, shading, string mismatch, blown fuse, tripped RCCB, or inverter derating; check error codes first.

Performance verification: compare actual kWh and performance ratio against expected values; a PR below about 0.70 warrants investigation.

Electrical shock prevention: PV modules generate voltage whenever illuminated; treat DC conductors as live, cover modules during work, and never work alone on live DC.

Working at height: use fall arrest harness, guardrails or scaffolding; anchor points must be rated; ladders at 75° with a 1 m extension above the landing.

PPE: insulated gloves, safety helmet with chin strap, safety shoes, goggles, and arc-rated clothing for DC/AC work; inspect PPE before use.

Lockout/tagout: isolate AC and DC, lock the isolator, tag with name and time, verify zero voltage, and only the person who applied the lock removes it.

First aid for electric shock: isolate supply, do not touch the casualty until de-energised; call emergency services; start CPR if trained and unresponsive; treat burns with clean dressing.

Arc flash and DC hazards: DC arcs do not self-extinguish at zero crossing; use DC-rated devices and never interrupt DC under load with non-DC-rated switches.

Battery safety: lead-acid emits hydrogen (no flames/sparks, ventilate), electrolyte is corrosive (eye wash and acid spill kit); LFP needs fire-rated storage and no short circuits.

E-waste and battery disposal: route modules, inverters and batteries to authorised recyclers per E-Waste (Management) Rules and Battery Waste Management Rules; never burn or landfill.

Site safety: barricade work area, check roof load capacity, secure tools and modules against wind, and maintain a first-aid kit and fire extinguisher (CO₂/ABC).

Ohm's law: V = I × R; power P = V × I = I²R = V²/R; energy E (kWh) = P (kW) × time (h).

Series circuit: same current, voltages add; R_total = R1 + R2 + ...; a single open cell breaks the whole string.

Parallel circuit: same voltage, currents add; 1/R_total = 1/R1 + 1/R2 + ...; a shorted branch affects the rest.

DC basics: unidirectional current from PV; AC basics: sinusoidal, frequency 50 Hz in India, RMS values used for power calculations.

Power factor: real power P = V × I × cos φ; inverters usually operate near unity power factor for grid export.

Semiconductors: p-n junction diode conducts in forward bias and blocks in reverse; a PV cell is a large-area p-n junction.

Bypass diode: forward-biased when a cell group is shaded, protecting against hot spots; blocking diode prevents reverse current into a weaker string or battery at night.

Temperature effect: Voc falls with rising temperature; use the datasheet Voc temperature coefficient to correct field measurements to STC.

Three-phase basics: line voltage = √3 × phase voltage; power P = √3 × V_L × I_L × cos φ for balanced three-phase loads.

Quotation basics: itemise modules, inverter, structure, cabling, BOS, labour, transport, GST and warranty; state payment milestones and validity period.

Costing: total cost = material + labour + overheads + contingency; margin added on cost or price; break-even = fixed costs / (price - variable cost per unit).

Documentation: site survey form, single-line diagram, bill of materials, test/commissioning report, warranty cards, and handover checklist signed by the customer.

Government schemes awareness: PM Surya Ghar: Muft Bijli Yojana (rooftop subsidy for residential), net metering rules of the state DISCOM, and MNRE empanelled-vendor requirements.

Customer handling: explain generation estimates, payback period, warranty terms and maintenance schedule in simple language; record complaints and close them with a service report.

Soft skills: punctuality, clear communication, active listening, teamwork on site, and respectful behaviour with the customer and DISCOM officials.

Workplace practices: follow the SOP, maintain tools and PPE, keep a daily work log, and report incidents; safety compliance is part of employability.

Warranty terms commonly quoted: module performance warranty 25-30 years, inverter 5-10 years, structure 5-10 years, workmanship 1-5 years.

Net metering and subsidy paperwork: application to DISCOM, feasibility approval, installation by empanelled vendor, net meter installation, and subsidy claim through the national portal.