Transcript PPT - Hss-1.us

PV System Design and Installation
LO 10 Performance Analysis and Troubleshooting
Performance Analysis and Troubleshooting
(7% of test questions)
Task/Skill
10.1. Describe typical system design errors
10.2. Describe typical system performance
problems
10.3. Associate performance problems with
typical causes
10.4. List equipment needed for typical
system performance analysis
10.5. Compare actual system power output
to expected
10.6. Identify typical locations for
electrical/mechanical failure
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.
2.
3.
4.
Take irradiance temperature and
measurement.
Apply correction factors
Measure Isc (current) and Voc (voltage)
being produced by the array
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
1.
Loose, broken or pinched wires
2.
Loose connections
3.
Rodent damage
Reference 3
Current Paths
Ground Fault
Protection
Normal Operation
Current Paths
Positive Ground
Fault
Current Paths
Negative Ground
Fault