Feature sponsored by Test & measurement Q
What are the risks of PV installation/maintenance for technicians?
The high DC voltage in solar systems could create arc faults or spark fires. Besides the electrical hazard there is a high risk of thermal danger which could lead to fire or explosions.
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TOP TIPS FOR SOLAR INSTALLATION TROUBLESHOOTING USING THE FLUKE 393 FC CAT III 1500 V CLAMP METER
TROUBLESHOOTING PV PANELS A technician should first check the output of the entire system at the metering system or inverter. Before commencing troubleshooting, also check and record the inverter’s input voltage and current level from the array. The combiner box can be a great place to
How does the 393 FC protect workers against electrocution and arc flash events?
The CAT III 1500 V safety rating of the Fluke 393FC Clamp Meter helps to protect against the three main electrical hazards – shock or electrocution from energised conductors, and arc faults that spark fires and arc flash. This safety rating provides higher creepage and clearance distances and withstands much higher test voltages. However, it is important for technicians and first responders to be aware of safety and control measures to rapidly shutdown systems and reduce shock or electrocution hazards as required. It’s not just about selecting CAT- appropriate equipment for the voltage they are working on. Arc flash mitigation in PV systems is divided by DC (before the inverter) and AC (after the inverter). DC-side mitigation for large solar arrays (100 kW +), is especially important at the combiner box where multiple strings of solar panels are combined in parallel to increase the current. To reduce the potential for arc flash, large-scale systems can use multiple string inverters that themselves can connect multiple strings in parallel, instead of using one or two large central inverters that require combiner boxes. AC-side mitigation includes arc resistant switchgear, which redirects arc flash energy through the top of the enclosure, away from personnel and equipment. Technicians should wear appropriate PPE, including arc-rated clothing, gloves, safety glasses or goggles, hearing protection, and leather footwear. Other key considerations which can impact safe work practices on PV systems include using high- quality test leads, high-energy fuse replacements and the correct probes and accessories.
troubleshoot the system because the individual wires from the modules are brought back to it. Each module may have a fuse that should be checked with the Fluke 393 FC. Wiring problems and loose connections
may cause a module to produce a voltage that is too low. These can be traced out using the Fluke 393 FC to check wiring connections at the junction boxes. The Fluke 393 FC provides an audio polarity warning when testing Voc. If the polarity is reversed, it may mean that other circuits in the combiner box are unintentionally connected in series, resulting in voltages over the maximum inverter input voltage.
TROUBLESHOOTING PV LOADS Start by checking the load switches, fuses, and breakers with the Fluke 393 FC to see if the correct voltage is present at the load’s connection. Next, check the fuses and circuit breakers. Find and replace blown fuses or tripped breakers. If the load is a motor, an internal thermal breaker might be tripped or there might be an open winding in the motor. For testing purposes, plug in another load and see if it operates properly. As with any electrical system, check for
broken wires and any loose connections. Clean all dirty connections and replace all bad wiring. With the power off, check for and repair any ground faults. If any fuses blow or breakers trip again, there will be a short that will need to be located and repaired. If the load still does not operate properly, use the Fluke 393 FC to check the system’s voltage at the load’s connection. The wire size may be too small and need to be increased. This will show up as a low voltage at the load and to resolve either reduce the load on the circuit or run a larger wire.
TROUBLESHOOTING PV INVERTERS The inverter converts DC from the PV system into AC power for building use. For troubleshooting the AC side, use the Fluke 393 FC to check the inverter’s output voltage and current levels. Many of these systems have a display that indicates current inverter and system performance. As the Fluke 393 FC produces a true-rms reading, you can use the voltage and current to measure and record the power output in kilowatt (kW). If possible, use the inverter display to show the current total energy in kilowatt hours (kWh) and compare it to the one recorded during the last inspection. When troubleshooting the DC side, use the Fluke 393 FC to check the DC power and save the reading to the Fluke Connect app on your phone. If the inverter does not produce the right amount of power, there may be a blown fuse, tripped breaker or broken wires - all of which can easily checked with the Fluke 393 FC.
TROUBLESHOOTING COMBINER BOXES When troubleshooting combiner boxes, amperage measurements and calculations are crucial to establishing whether the PV arrays are operating correctly. Measuring current on individual arrays or combining current measurements will help determine if a module has malfunctioned. The thinner jaw design of the Fluke 393 FC clamp meter ensures several conductors are used in the jaw for combined current measurements, even in tight or crowded spaces like inverter or combiner boxes.
Q 24
Where can our readers find out more about the Fluke 393 FC CAT III 1500 V True-RMS Clamp Meter?
For more information about the Fluke 393 FC CAT III 1500 V True-RMS Clamp Meter, please visit:
www.fluke.com/en-gb/product/electrical-testing/clamp-meters/393-fc Alternatively, go to the Fluke home page, select “Products” and “Solar industry tools” to view
Fluke’s comprehensive range of instruments for solar applications including Fluke 1577/1587 and the IP67 rated multimeter Fluke 87V MAX. Access this information directly by going to:
www.fluke.com/en-gb/products/electrical-testing/best-solar-energy-industry-tools
Fluke
www.fluke.com September 2022 Instrumentation Monthly
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