The role of the combiner box is to bring the output of several solar strings together. Daniel Sherwood, director of product management at SolarBOS, explained that each string conductor lands on a fuse terminal and the output of the fused inputs are combined onto a single conductor that connects the box to the inverter. “This is a combiner box at its most basic, but once you have one in your solar project, there are additional features typically integrated into the box,” he said. Disconnect switches, monitoring equipment and remote rapid shutdown devices are examples of additional equipment.
Solar combiner boxes also consolidate incoming power into one main feed that distributes to a solar inverter, added Patrick Kane, product manager at Eaton. This saves labor and material costs through wire reductions. “Solar combiner boxes are engineered to provide overcurrent and overvoltage protection to enhance inverter protection and reliability,” he said.
“If a project only has two or three strings, like a typical home, a solar combiner box isn’t required. Rather, you’ll attach the string directly to an inverter,” Sherwood said. “It is only for larger projects, anywhere from four to 4,000 strings that combiner boxes become necessary.” However, combiner boxes can have advantages in projects of all sizes. In residential applications, combiner boxes can bring a small number of strings to a central location for easy installation, disconnect and maintenance. In commercial applications, differently sized combiner boxes are often used to capture power from unorthodox layouts of varying building types. For utility-scale projects, combiner boxes allow site designers to maximize power and reduce material and labor costs by distributing the combined connections.
The combiner box should reside between the solar modules and inverter. When optimally positioned in the array, it can limit power loss. Position can also be important to price. “Location is highly important because a combiner in a non-optimal location may potentially increase DC BOS costs from losses in voltage and power,” Kane explained. “It only constitutes a few cents per watt, but it’s important to get right,” Sherwood agreed.
Little maintenance is required for combiner boxes. “The environment and frequency of use should determine the levels of maintenance,” Kane explained. “It is a good idea to inspect them periodically for leaks or loose connections, but if a combiner box is installed properly it should continue to function for the lifetime of the solar project,” Sherwood added.
The quality of the combiner box is the most important consideration when selecting one, especially since it’s the first piece of equipment connected to the output of the solar modules. “Combiner boxes are not expensive compared to other equipment in a solar project, but a faulty AC combiner box can fail in a dramatic way, involving shooting flames and smoke,” Sherwood warned. “All should be third-party certified to conform to UL1741, the relevant standard for this type of equipment,” Sherwood said. Also be sure to pick a combiner box that meets the technical requirements for your project.
A new trend is the incorporation of a whip: a length of wire with a solar connector on the end. “Rather than a contractor drilling holes in the combiner box and installing fittings in the field, we install whips at the factory that allow the installer to simply connect the output conductors to the box using a mating solar connector,” Sherwood explained. “It’s as easy as plugging in a toaster.”
This year arc-fault protection and remote rapid shutdown devices are more popular than ever, due to recent changes in the National Electrical Code that require them in many solar applications. “New technologies and components are driven by the NEC changes, as well as the desire for enhanced energy efficiency and reduction of labor costs,” Kane said. Some of these new components include: higher voltage components, integral mounting hardware and custom grounding options.
A photovoltaic power plant is a photovoltaic power generation system that uses the sun's light energy and electronic components such as crystalline silicon panels and inverters to generate electricity that is connected to the power grid and delivers power to the grid.
The PV power generation system consists of solar arrays, battery packs, charge/discharge controllers, inverters, AC power distribution cabinets, solar tracking control systems, and other equipment. The PV power generation system usually consists of PV modules, inverters, PV distribution boxes, meters, and power grids, and the distribution boxes, although the surge protective device is not accounting for a high percentage of the total system cost, but play an important role in the PV power generation system.
Solar energy is an inexhaustible source of renewable energy, which is sufficiently clean, absolutely safe, relatively widespread, really long-lived and maintenance-free, resource-sufficient and potentially economical, etc., and plays an important role in long-term energy strategies. Photovoltaic power plants are currently among the most strongly encouraged green power development energy projects. The use of limited resources to achieve the maximum amount of energy for human use.
Power Distribution Boxes in Photovoltaic Power Plants
Photovoltaic power generation is developing rapidly in China, and the application of photovoltaic in all aspects of life has been reflected. Household photovoltaic power stations, large photovoltaic ground power stations, photovoltaic buildings, photovoltaic street lights, photovoltaic traffic lights, photovoltaic caravans, photovoltaic electric vehicles, photovoltaic carports, and more and more electricity-using environments have a photovoltaic figure, in which the photovoltaic box plays a vital role in the entire photovoltaic system, the main functions of which are as follows:
1. Power isolation function
Switchboards require a physical isolation device that allows the circuit to have a sharp break-point for the safety of personnel in service and maintenance situations. This device is called an isolation switch, which could ensure safety while the electricity has a short circuit, and the current increases and cause the cut off of the isolation switch.
2、Short circuit protection function
Once a short-circuit occurs in a circuit, it will cause a sudden increase in current, which will burn out the appliance and generate a lot of heat, making it susceptible to fires, with serious consequences. Therefore, when a short circuit occurs, a device is needed to cut off the power. The air switch is the device, which occupies an important role in the PV box. When you choose the air switch, please try to use reliable products and choose reliable manufacturers to ensure safety.
Generally, PV energy meters are installed together with the DC surge protective device. There are also some places where the meter is separate from the distribution box. You can choose according to the local power supply department.
The majority of distributed PV power generation is connected to the rural power grid. One of the characteristics of rural grids is that they are unstable, it is common that the power outages usually, and the voltage fluctuates greatly. In this case, the PV distribution box has a device indispensable, that is, an under-voltage protector. In the case of over-or under-voltage, it acts as a circuit breaker to protect other components. Under-voltage protection in the entire photovoltaic box, is more prone to failure of accessories, even if maintenance and replacement are required.
Lightning is also a common natural phenomenon in life, especially in the summer, the thunderstorms are frequent happened and many accidents happened to people, Lightning is a scary thing in life, and there are lightning protectors in many places. There is also an important lightning protection device in the distribution box - the surge protector. A surge protector, also called a lightning protector, is an electronic device that provides safety protection for different electronic equipment, instruments, and communication lines. When the electrical circuit or communication lines because of external interference in the sudden generation of current or voltage, the surge protector can be turned on in a very short period of time to shunt, thereby reducing the circuit damage to other equipment, is an indispensable component.
6、About the cabinet
Generally speaking, the design service life of photovoltaic power generation is 25 years, so the distribution box should be used for 25 years, requiring a waterproof and dust-proof function. With the development of society and the progress of the times, the original distribution box made of cheap tin was not up to the requirements. Now the power supply bureau generally requires to use the of galvanized plate spray plastic, iron plate spray plastic, stainless steel, plastic steel, and other materials of the distribution box. Otherwise, you will forbid to the parallel network, in order for your safety, choose the appropriate box is very important.
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