PV System Design and Installation LO 10 Performance Analysis and Troubleshooting

Task/Skill Describe typical system design errors Describe typical system performance problems Associate performance problems with typical causes List equipment needed for typical system performance analysis Compare actual system power output to expected Identify typical locations for electrical/mechanical failure Performance Analysis and Troubleshooting (7% of test questions)

Overall PV System Efficiencies PV Array Input (DC) = 70 to 80% AC Output (AC) Reference 2

Typical Design Errors General Issues 1.Not accounting for shading issues (trees, chimneys, inter-row spacing, etc.) 2.Inadequate structural support (wind, snow, seismic and dead loads) Inverter Issues 1.Under/oversizing PV array relative to inverter capacity 2.Too many modules in a string (Voc x Temp Correction < Max Inverter DC input) 3.Too few modules in strings (Vmp with temp correction to make sure that do not drop below inverter cut-off voltage) 4.Under sizing wires for voltage drop (see voltage drop formula) NEC Issues 1.Under sizing overcurrent protection devices (Isc - fuses and circuit breakers) 2.Under sizing wires for ampacity requirements (Isc – wire sizes, conduit fill and temperature correction factors, etc.) 3.Equipment labeling

Performance Analysis and Trouble Shooting Tools 1.Basic tool kit (screw drivers, etc) 2.Irradiance meter 3.Multimeters DC Voltage DC Current (Clamp-on / Hall Effect) AC voltage (RMS) AC current (RMS) 4. Hydrometer (battery systems)

PV System Problems from 1000 Solar Roof Project in Germany Reference 2

Check Site Conditions 1.Module Condition 2.Array Condition 3.Roof condition 4.Array Shading 5.Inverter Condition (error messages, signs of charring, unusual noises, hot spots) 6.Wiring (connections, insulation abrasion, discoloration)

Check Performance Inverter Efficiency = Displayed AC Power Array Imp x Array Vmp Array IV Curve 1.Take irradiance temperature and measurement. 2.Apply correction factors 3.Measure Isc (current) and Voc (voltage) being produced by the array 4.Compare theoretical to practical

Check for Ground Faults 1.Possible signs 2.Voltage-to-ground from PV module frames, rack, inverter and other equipment. 3.Blown Ground Fault Fuse (> 1 amp fault) 4.Error code (minor fault) 5.Isolate and test individual module strings Causes Reference 3 1.Loose, broken or pinched wires 2.Loose connections 3.Rodent damage

Current Paths Ground Fault Protection Normal Operation

Current Paths Positive Ground Fault

Current Paths Negative Ground Fault