Operations and Maintenance (13.3%)

PVA · 40 questions

• A small business wants to sell solar credits that pay by the kilowatt-hour and the utility requires audited production data with tight error limits. The crew installed a standard inverter display and a consumption CT set. Which monitoring choice describes revenue-grade metering for credit payments?
• A homeowner calls three months after install because a 6-kW rooftop system shows 12% lower monthly energy, with pollen season, nearby tree growth, pigeon nesting under edge modules, and no breaker trips reported. Which loss explanation best accounts for this deviation from expected performance?
• During O&M on a 12-module string reading low power at midday, the inverter display reports only 380 V on the string while the tech expects about 480 V open-circuit, with intact wiring and no shade. The lead asks for a safe first electrical check. Which multimeter task isolates the voltage fault correctly?
• During commissioning of a 12-module string, you capture an IV curve on a sunny day to verify health before handoff. The curve shows zero-current voltage, zero-voltage current, and a knee where power peaks. Which IV curve reading correctly identifies Isc, Voc, and maximum power point for this string?
• During commissioning of a 12 kW rooftop array, a tech uses a handheld tracer on one string at midday and records open-circuit, short-circuit, and peak-power values to compare with the datasheet. The crew leader asks for a clear field reading of curve points. Which reading best identifies Isc, Voc, and maximum power point?
• A maintenance tech must check an older 600-V string for degraded insulation after a ground fault cleared. The array can be isolated, the sun is up, and the crew has lockout gear. Which use of an insulation tester (megohmmeter) yields a valid reading safely?
• A 120-kW rooftop system for a grocery store shows healthy irradiance and no faults, yet output flatlines at 50 kW on sunny afternoons per the utility interconnection agreement that caps export to protect the feeder. Which curtailment and export-limitation behavior best explains this deviation from expected performance?
• An O&M tech is chasing repeated ground-fault alarms on a 3-year-old rooftop string that reads low isolation resistance at the inverter. The array is de-energized, LOTO applied, and conductors are isolated for testing in dry daylight. Which insulation tester practice gives a valid leakage check that shows which conductor is leaking?
• You maintain a 12-kW rooftop array with central monitoring. On a clear day the site pyranometer drops from 1000 to 400 W/m2 when thin clouds pass, cell temperature stays near 25C, and the inverter stays online with no faults. Output current falls sharply while DC voltage dips only slightly. Which performance statement best explains this irradiance effect?
• You maintain two identical 10-kW rooftop systems in Phoenix. At 9 a.m. under light haze both show 610 Vdc and 6 A, and at solar noon under clear sky both show 625 Vdc and 14 A. Your supervisor asks for a status note. Which statement correctly explains irradiance effects on performance parameters?
• You maintain a 250-kW rooftop with bifacial modules where output dropped 8% on clear windy days. The pyranometer looks dusty and tilted, no rear-irradiance data exists, and wind logs are missing. Which weather sensor action best diagnoses irradiance, bifacial gain, and cooling effects?
• A 40-kW commercial rooftop array underperforms on clear days after visual inspection shows no major soiling or shade. The O&M lead assigns IV curve tracing on suspect strings. Which IV curve tracer practice should the technician use to isolate the electrical fault?
• A tech supports a 48 V lead-acid battery bank at a remote irrigation site. The controller has used one fixed absorb voltage since commissioning, the cabinet swings from near freezing at dawn to hot by afternoon, and the pump runs all night while the array starts before anyone arrives. The operator wants to know how much pumping time is left. Which two monitoring inputs should he fit?
• An O&M tech inherits a 60-kW rooftop system with nuisance trips, faded wire labels, and no history after the original installer closed, and the owner wants reliable troubleshooting going forward. Which record-keeping practice best supports safe maintenance of this PV system?
• You service a 9-kW home system in Charlotte with a string inverter listed 200-500 Vdc MPPT range and 600 Vdc max, plus 240 Vac output. On a cold morning it shows 545 Vdc at low power and frequent restarts. Which interpretation of inverter AC/DC voltage and MPPT range best explains the fault?
• During a noon maintenance visit on a 25-kW rooftop array with one warm combiner fuse and normal inverter output, the tech carries an IR thermometer and a thermal camera. Which diagnostic use of the IR thermometer and thermal camera should the tech choose to locate the heat fault safely?
• A maintenance lead suspects soiling plus one weak bypass diode in a 12-module string after a hot dusty month. Open-circuit voltage looks near normal, but midday power sags and infrared shows one hot module. Which IV curve tracer use best isolates the fault?
• You are checking a 6-kW residential string inverter at midday that lists 230-V AC output and a 200-480-V MPPT range, and the monitoring portal shows 180-V DC input with low power during full sun and no shade or faults logged. Which interpretation of inverter AC/DC voltage and MPPT range best explains the reduced performance?
• During a midday O&M visit for a 12-kW rooftop string with low output, you suspect a hot fuse holder and one warmer module section. Ambient is 28C, wind is calm, and the array is under steady sun. Which instrument practice should you use to screen with the IR thermometer and thermal camera?
• During commissioning of a 10-kW hybrid system with backup, the grid sags on a hot afternoon, frequency wavers, and the battery bank reads low after overnight loads. Which relationship among utility voltage and frequency and battery voltage and state of charge should the technician use to explain operation?
• During O&M training, techs compare a 400-W nameplate to lower midday field output on a warm roof with light wind. The data sheet lists both STC and NOCT ratings. Which comparison of STC and NOCT test conditions best sets expected performance?
• A technician visits a 5-year-old 12 kW rooftop array after a hailstorm and high winds for a scheduled O&M check with no monitoring alerts. Production looks normal on the app. Which visual inspection routine best fulfills maintenance of PV systems?
• A six-month-old 8-kW rooftop string system shows one string 18% low at solar noon with no inverter fault, clean sky, and matching tilt. Thermal scan shows one hot bypass area and a shaded lower corner from a new vent pipe. Which installation deficiency diagnosis is correct?
• A maintenance tech must verify a suspected soiling loss on a 50-kW roof array at solar noon on a clear day, comparing meter readings to expected output and the monitoring portal. Which irradiance meter practice yields a trustworthy check?
• A two-person O&M crew is checking a 12-kW roof array that reads low at midday with no tripped breakers, clean sky, and a south tilt of 28 degrees. The lead asks for a plane-of-array sun check to compare output to expected watts. Which irradiance meter technique should the crew use to verify expected array output?
• You are the O&M tech at a 200-kW rooftop site where an inverter cooling fan has seized after six years, and the spare kit is on site. The disconnects for AC and DC are locked only by you, and the site log requires service dates for wear parts. Which lockout/tagout and service-life replacement procedure should the technician follow for the fan assembly?
• A homeowner with a 7 kW rooftop system reports low credits for two weeks, the installer sees normal status on the fleet web portal, and the homeowner wants daily checks without a site visit. The inverter display on-site shows no fault code. Which monitoring method best fits ongoing homeowner daily checks and remote troubleshooting support?
• A home has a battery-based inverter tied to the grid with backup loads. During a storm the lights flicker, the inverter disconnects from the grid and powers backup loads, then it shuts down overnight even though solar is idle. Morning checks show grid sag with unstable frequency and very low battery voltage. Which operating relationship among utility voltage and frequency and battery voltage and state of charge explains the shutdown?
• During maintenance on a flooded lead-acid off-grid bank, one string shows low voltage under load, full electrolyte levels, and clean terminals after an equalize charge. Which electrical test equipment choice correctly uses a load tester, hydrometer, and refractometer to diagnose battery condition?
• An O&M tech is servicing a small off-grid cabin with four flooded lead-acid batteries showing uneven run time, low specific gravity alarms, and sulfation risk after a cold week. The owner wants cell-level health before equalizing. Which battery test sequence should the tech use with load tester, hydrometer, and refractometer?
• A technician at a 750 kW carport array is told the SCADA power trend has been flat since 06:12, while every inverter's front panel shows normal output and no alarms. The site collects field data through a data logger that polls the inverters and meter before sending values to the SCADA host. Which data acquisition check should the technician run first to locate the break in the monitoring path?
• During O&M on a 50-kW roof system the dashboard shows low output, the crew hears buzzing at a combiner, and smells hot plastic near cracked conduit. Which fault recognition should the tech apply to distinguish arc faults from ground faults?
• An O&M tech supports 30 homes with app access plus a fleet web portal and local inverter screens. One owner reports low credits but shows only a green light, the office needs fleet faults, and the site has no phone signal for remote checks. Which monitoring method comparison among app, web, and on-site best directs each troubleshooting need?
• You service a 25-kW dusty rooftop array at noon in Arizona with warm modules, visible soiling, and prior hot connections. The manual lists connector torque values and allows only soft cleaning with low-mineral water. Which torque and cleaning practice best protects performance and connection safety?
• An O&M tech inherits a 250-kW rooftop portfolio where inverters log locally but owners get no alerts, and a new SCADA scope is proposed. Which description correctly states what data acquisition and SCADA should provide for this fleet?
• A 10 kW rooftop system in Texas shows lower midday power on a 104F calm afternoon than on a breezy 85F morning, though sunlight looks equally bright and no clouds or soiling are found. The owner asks why heat and wind matter. Which explanation best describes temperature and wind effects on output?
• At a 30-kW shop the portal shows solar output far below the inverter screen, and the tech finds small doughnut sensors around the feeders plus small boxes tied to voltage leads in the monitor panel. Which monitoring equipment explanation correctly describes current and potential transformers?
• A 50-kW rooftop array in a desert town shows lower midday summer power than its nameplate suggests, but output rebounds on cool windy afternoons despite identical sunlight. The owner suspects soiling only. Which temperature and wind effect explanation should the technician give for performance parameters?
• A crew lead asks how a multimeter can check continuity of the equipment bonding path from a module frame to the designated equipment grounding point. Which demonstration best checks that path’s continuity?
• A high-desert 10-kW array with white gravel logs midday power 8% above model on a cold, clear, windy day with puffy clouds, even though the sun angle is low. The tech sees brief spikes as clouds pass and snow glare from nearby drifts. Which factor set best explains these production gains?