Smart fault discrimination for large-scale PV systems - a DC combiner sets new standards
The increasing output of ground-mounted photovoltaic systems is presenting operators and service teams with ever more complex challenges. Particularly in systems with central inverters, a single defective string can lead to the shutdown of an entire system section in the megawatt range. This not only causes yield losses, but also high service costs due to time-consuming troubleshooting.
Q3 ENERGIE GmbH & Co. KG has developed a practical answer to this problem: The new Q3 Super Multi Box, a DC combiner with patent-pending fault discrimination technology.
One string combiner box - many functions
The Q3 Super Multi Box is a highly developed generator connection for large-scale PV systems with central inverters. It combines numerous safety and communication functions in an IP66 sheet steel housing:
⚙️ Single string current measurement for up to 24 inputs
⚙️ Electronic DC disconnection up to 480 A at 1,500 V DC
⚙️ Integrated PV fault manager with remote maintenance
⚙️ SPD T1+2 with remote signaling contact
⚙️ Fuses in the positive and optionally also in the negative pole (32 A / 1,500 V DC)
⚙️ Communication interfaces: Modbus TCP/IP, RS485, Ethernet or USB
⚙️ MC4-EVO2 input contacts and copper rail outlet
The electronics are supplied directly via the PV strings using DC/DC converters. At night, the system remains able to communicate thanks to battery buffering.
Innovation: The "PV string error discriminator"
The DC combiner contains a patent-pending technology for selective fault detection at string level. If a fault occurs (e.g. insulation fault or electric arc), all strings in a box are first switched off. This is followed by automatic connection string by string until the fault is clearly localized. The affected string is permanently isolated, the other strings continue to run. System availability is maintained and service work can be planned in a targeted manner.
This eliminates days of yield losses and manual search processes in the field, which were previously common for large-scale systems. The "PV String Fault Discriminator" represents a paradigm shift in the maintenance of large-scale systems.
Practical benefits for operators and service
The advantages of the Q3 Super Multi String Combiner Box are particularly evident during operation:
⚙️ Yield protection: only the defective string is isolated
⚙️ Faster maintenance: automatic fault localization
⚙️ High compatibility: connection to SCADA systems or inverters
⚙️ Modular design: adaptable to project-specific requirements
"An insulation fault is not uncommon in open-air systems. The new Q3 technology saves us days of troubleshooting - and therefore money!"
- said a visitor to the Q3 stand at Intersolar 2025.
Development from practice
Q3 ENERGIE GmbH & Co. KG has been developing technical safety solutions for PV systems for over 15 years. Q3 ENERGIE is one of the leading technology companies in the field of firefighting switches in Germany. The Q3 Super Multi Box arose from specific customer requirements for string combiner boxes: defective individual strings should no longer paralyze entire parks.
Based on the proven QFire technology, an automated single-string disconnection was developed and linked to intelligent communication. The prototype was developed in less than a year and was completed in time for Intersolar 2025. A patent application for the associated technology was filed in May 2025.
Market entry and outlook
The Q3 Super Multi String Combiner Box will be in series production from the third quarter of 2025. Project-related planning and quotations are now possible. As Q3 manufactures to order, delivery times of several weeks can be planned - a calculable factor for large-scale projects.
In future, Q3 plans to cooperate closely with manufacturers of central inverters in order to ensure compatibility and functional reliability at an early stage.
Conclusion: The Q3 Super Multi Box is more than just a string combiner box. It is an intelligent building block for the operational reliability of large PV power plants. With its new fault discrimination technology, it sets a new standard for efficiency, availability and safety.
Author: Thomas Neumann, Managing Partner of Q3 ENERGIE GmbH & Co. KG
Link to the product:
>> https://q3-energie.de/produkte/combiner-box/