String combiners for solar photovoltaic systems
In a photovoltaic system, the modules are arranged in strings and fields depending on the type of inverter used, the total power and the technical characteristics of the modules. The connection of the modules in series is made on the modules themselves, while the parallel connection of the strings is made inside “String combiner boxes” that accommodate, along with the interconnection systems, also the overcurrent protection devices, disconnectors and surge protection devices.
The string combiner boxes form subsystems that can be standardized according to the number of strings, voltage and rated current.
For utility-scale installations, the combiners are equipped with monitoring devices to measure the current, voltage and temperature to ensure the availability of the strings and maximize generation.
ABB offers different product ranges, each dedicated to specific installation conditions with typical configurations.
- Plug and play
- Widest range to address residential, commercial and utility scale installations in 1000V and 1500VDC
- Global availability ensuring on-site delivery at any part of the world
- Mechanical features: IP66, IK10, GWT 750°C, UV and chemicals resistant
- Electrical features: double insulation (Class II), Ui/Ue: 1000V DC/1500V DC
- Wide range (in terms of number of strings and monitoring systems)
The installation of a photovoltaic system often occurs in complex logistic situations, critical from the environmental and time perspective. The availability of tested and certified pre-assembled components allows the installer to avoid unnecessary on site assembly, wiring and certification activities for the string boxes. String boxes enclose functions such as string protection, protection against overvoltage and disconnect, with components suitable for the string’s various voltage levels and the number of connected strings.
The string monitoring is an important function in running medium and large size installations, since it allows to improve the efficiency and maintenance of the system. ABB offers a series of pre-wired string boxes for all installation conditions: they are equipped both with devices necessary for string protection, surge protection and disconnection, and with useful devices for string monitoring to measure string current, voltage and temperature inside the enclosures.
The development and the increasingly frequent adoption of multi-string inverters mainly in residential applications has made it necessary to reduce the costs and the space occupied by the string boxes, to bring together in a single combiner box with the protective devices and disconnectors of multiple strings intended to be connected to a specific inverter input. Multi-string inverters resolve in an easy and cost-effective way system conditions characterized by modules installed in different leaning and exposure positions or minimize the problems related to systematic shading of parts of the system.