Mark Bakker, field application engineer at Fluke Corporation, looks at the importance of power quality measurement for solar installations from the ground up.
The advantages of trading in fossil fuel power generation for renewable energy resources are undeniable. There has been significant growth in renewable energy generation across Europe over the last decade.
Solar Power Europe reported in their recent annual report that the number of solar installations across Europe has increased by a third in 2021 to almost 26 Gigawatts (GW). The growth of wind power in Europe far exceeds that of solar and is estimated to expand by a further 105 GW over the next five years according to Wind Europe.
The reason for the increase is likely to be because governments around the world are further strengthening policies aimed at reducing carbon emissions, considered a major contributor to global heating, and achieving net zero. Many policies were put in place from the climate agreement made in 2015 at COP21 in Paris, however with more evidence coming to light in recent years, policies have been strengthened further.
It is not only policy change that is driving the global uptake of renewable energy. According to WE forum, the cost of photovoltaic electricity has fallen some 85% in the last decade. The rise in solar installations is continuing around the world.
How energy from the sun is harvested
There are ways of harvesting the thermal energy from the sun to heat water for use in the home. It can also be collected using mirrors to focus the sun’s energy and heat water to the temperatures required to motivate steam turbines.
By far the most common form of gathering the energy from the sun is by using photovoltaic (PV) panels that transform the energy in the sun’s photons to knock electrons from atoms and cause a flow of electricity. This dynamic growth in photovoltaics for electricity production, is creating an ever-increasing demand for technicians who can manage, maintain and troubleshoot PV systems efficiently and effectively.
Testing power quality
Power quality is an important measure for industrial plants, manufacturing facilities and energy providers, as bad power quality can cause all sorts of problems for electrical equipment including lighting, computer systems, drive systems and motors.
Harmonics can cause problems in infrastructure components like conductors and transformers t whereas transients, sudden spikes in voltage, can cause sensitive electronic equipment failure. Power quality testing often requires technicians to collect data over a time period and analyse the results.
Demand for renewable power quality
As the transition to renewable energy accelerates it’s critical that installers and maintenance staff have access to the right training and instrumentation to get solar farms online fast and keep them working at peak performance. There has been an increase in demand for high-precision handheld devices, which can measure photovoltaic (PV) systems.
The output of solar panels is continually fluctuating. An inverter will convert the DC to AC, but an unconditioned AC voltage can cause various power quality issues.
In commissioning it is important for owners and investors to determine if the installed equipment can deliver the output that the solar plant was designed to deliver. The output must comply with certain quality standards and again this can be verified using power quality test equipment.
Testing power quality safely
When it comes to solar, a crucial consideration when selecting a tool for power quality maintenance and troubleshooting is having just one instrument capable of measuring DC as well as AC, so that the technician can do a function check on a solar panel and have the ability to measure AC after the inverter, of equal importance is a tool that will display results in real time.
Photovoltaics transform energy from the sun’s radiation into electricity, however the energy produced is ‘wild,’ fluctuating with the strength of the sun and can cause safety issues.
There is an exciting new development in power quality testers that can further improve the safety of operators in the field. An auto-correct feature allows the user to connect the probe and move away. Once connected it is possible to adjust and make correction to the connection on the display or remotely via their smartphone, minimising their exposure to high-voltage terminals.
Bridging the skills gap
With the scale of growth in the solar energy and wind power industry at this time, the number of skilled operatives is not keeping pace with the demand. In order to make testing as simple as possible, testers are now incorporating fool proof guided set up and allows the user to build custom views quickly and easily. A useful development in measurement technology is the capability of the instrument to start logging data automatically so even if the operator forgets to set up a parameter, the data can be drawn from the log file later.
The best equipment for troubleshooting should always come with a solid software package that will assist with analysis of events on the network. This software should also review the electrical signals in the log file, completing the analysis for you. Real time analysis will assist troubleshooting should any issues arise. For example, if a conductor gets hot in the solar panel network, then you can hook up the power quality test equipment to the conductor and test the current and voltages going through the conductor in real time. This allows the operator to relate the results directly to the processes that happen around them.
Continuous testing cycles
Maintaining regular test cycles in this way is allowing energy producers to monitor trends in the data collected on power quality. Beyond the primary measure of determining the power output needs, the trends in data collected by can help pinpoint faults, and plan preventive maintenance accordingly. Test equipment is helping solar and wind farms to use data to predict future events and ensure the safety of its operatives maintaining the PV systems and wind turbines. Preventive maintenance can also help avoid costly downtime and outages.
Troubleshooting across the system
When it comes to troubleshooting a PV system, maintenance routines typically focus on four parts of the system: the PV panels, load, inverter and combiner boxes.
Troubleshooting PV panels
A technician should first check the output of the entire system at the 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 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.
Troubleshooting PV loads
Start by checking the load switches, fuses, and breakers 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, 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, check the inverter’s output voltage and current levels. 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 right equipment.
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.
Using a clamp meter with a thinner jaw design ensures several conductors are used in the jaw for combined current measurements, even in tight or crowded spaces like inverter or combiner boxes.