By Jeffrey R. Jowett, senior applications engineer, Megger
Workplace safety is important in any field. Knowing how to use tools, equipment and machinery properly, as well as suiting up in all the necessary safety gear to perform your job can keep you from damaging equipment or getting seriously injured. This is especially true when dealing with the electrical grid, such as when installing and maintaining PV systems.
When designing, installing and maintaining PV systems, workers should pay close attention to strict guidelines and directions to help reduce or eliminate installation errors, electrical errors and injuries. Current coming from these systems can sometimes be erratic, and dangers can be hidden in things like ground faults or wiring. Knowing best practices and what to look for will help mitigate risk.
What can go wrong
Workers in the solar energy industry are exposed to a multitude of serious hazards while working with PV systems. These hazards include arc flash, which is when there is a high-power discharge of electricity between two or more conductors that can cause burns or even death; as well as insulation deterioration that can cause a fire; electric shock from a system’s loose wiring or tools and wiring that are not grounded or double insulated; thermal burns that can cause serious injury or death; as well as falls.
When it comes to solar electric systems, there are two sources of electricity: the utility and the solar electric system. Simply turning off a main breaker doesn’t stop a solar electric system from producing power. Modules always have some sort of voltage, even in low light. If handled improperly, it can lead to a shock or arc flash, which could cause serious injury or death.
Where issues occur
In PV systems, most issues arise in the combiner box, PV source and output circuit conductors, and the equipment grounding conductor. But issues can be avoided if workers take the time to install and maintain them properly. After installation, at least bi-annual maintenance is needed, especially if the modules are tilted. When modules are moved out of alignment due to natural events like weather and damage from human or animal contact, the efficiency of the string/array is affected. Misalignment can lead to adverse production in the array regarding maximum power delivery to the grid. Alignment must be corrected with an IR radiance tool like the Megger PVM210 in order to bring the module back into maximum efficiency alignment. There are monitoring apps that can help owners track the amount of solar energy the modules are producing. If there seems to be a dip in production, it’s either time to clean the modules or look further to see if there are other issues going on.
Identify a problem before it happens
O&M technicians can use a variety of tools to investigate problems with an array. These include a digital clamp meter, irradiance sensor, insulation resistance tester, as well as a thermal camera. Each tool has a specific job in identifying areas of concern, helping to correct the issue and keeping workers safe.
Digital clamp meter
A digital clamp meter measures the voltage output of PV modules to verify the performance of a PV array. It also provides solar technicians the ability to test higher voltages and current values with greater flexibility using a single tool. By using this tool, technicians can measure the intensity of the sunlight striking the arrays. This measurement is very important when validating the performance of a PV system.
This handheld tool measures the intensity of the sunlight striking an array. Measuring solar irradiance provides knowledge in making important decisions regarding future energy yield, efficiency, performance and maintenance.
Insulation resistance tester
An insulation resistance tester helps to perform insulation resistance testing during startup and maintenance activities to verify the integrity of conductors associated with a photovoltaic array. This tool can be used in residential, commercial and industrial rooftops, as well as large-scale ground-mount solar applications.
Periodic testing of the electrical cabling and components associated with solar PV systems helps to indicate the health of the system, identify potential issues early, ensure the safe operation of the system and reduce the risk of fire associated with potential or existing electrical faults.
A thermal camera helps to quickly and safely assess the PV modules as well as the junction boxes, combiner boxes and electrical connections for abnormal heat with a quick scan. The camera is used to locate bad cells, wiring or diodes. Each of these plays an important role in having the PV array run properly.
Cells are connected in series. When one cell in the series does not work, no current passes through that entire series, resulting in no electricity being generated. If an array is wired improperly or has failed, it might not deliver the appropriate voltage and fail to power up electrical units or result in the battery bank’s failure to charge fully. If a diode has gone bad, users will notice a drop in output.
Megger offers a Solar Test Kit with each of these tools to make a technician’s job easier.
Understanding PV systems, the dangers that lurk and how to safely test and maintain them is key in protecting workers and end users alike.