The DC‑INDUSTRIE2 project delivered a comprehensive system concept for industrial direct‑current networks, focusing on connector security, surge protection, voltage band operation, fault detection, and monitoring. The technical results are organised around five core components of a DC network: power supply units, DC‑to‑AC converters, DC‑to‑DC converters, DC‑busbars, and DC‑distribution panels. The project defined two nominal voltage bands, 540 V and 650 V, aligning with existing AC infrastructure and allowing the use of current components without major redesign. Regulated feed units (AIC) can generate DC voltages above the rectified AC level; for a 400 V three‑phase supply this requires about 650 V to avoid significant earth‑potential differences. Unregulated feeds produce a voltage that remains close to the AC level, simplifying integration.
Connector security was addressed by establishing five locking levels. Level 1 prevents accidental pull‑out, Level 2 requires a manual release such as a lever or notch, Level 3 demands a standard hand tool, Level 4 needs an authorised key or NFC‑enabled lock, and Levels 5a and 5b introduce automatic locking and unlocking controlled by a signal that verifies load‑free conditions or voltage measurement. The project validated all five levels in model plants, demonstrating that the highest level (5) can be realised with existing mechanical designs and signalling.
Surge‑protection devices were characterised for their ability to clamp transient over‑voltages in the microsecond range. The devices were tested in the TU BS and Weidmüller facilities, showing that the peak voltage can be reduced to safe levels without compromising the DC bus integrity. The study also examined the impact of surge protection on the overall network efficiency, confirming that the additional impedance does not significantly affect power quality.
Fault detection focused on serial arc faults, which can occur when a conductor breaks or a connector loosens. The project built a controlled test rig that introduced a variable gap in a DC‑sector feed and monitored the resulting arc. Spectral‑analysis‑based arc‑fault‑detection devices, common in the U.S. market (UL 1699B, IEC 63027), were evaluated. Because industrial DC networks contain many power‑electronic devices that emit broadband noise, the study identified false‑positive challenges and suggested filtering strategies. The research also explored passive protection measures, such as increased capacitance and reduced inductance, to suppress stable arcs.
An intelligent DC‑branch concept was developed and integrated with selective protection schemes. The model plants were equipped with pre‑load controls, surge‑protection devices, and monitoring hardware. The Weidmüller u‑control platform, combined with current and voltage transducers, enabled real‑time monitoring and load‑flow regulation. The monitoring system was validated in a HOMAG machine‑tool installation, demonstrating that the network can maintain stable operation across the defined voltage bands while automatically adjusting to load changes.
The project also produced a detailed analysis of installation materials—series clamps, electronic enclosures, and connectors—under DC loading. Measurements at TU BS and Weidmüller confirmed that there are no technical limitations compared to AC, supporting the claim that existing hardware can be reused in DC networks.
Collaboration was extensive. The consortium comprised 30 industrial partners, including ABB Stotz‑Kontakt, Audi, Danfoss, HARTING, Siemens, and the Technical University of Ilmenau, among others. Partners supplied components for the model plants, contributed to the system concept, assisted in building the test rigs, performed measurements, and co‑authored publications. The project ran until 31 March 2023, with the final report published on 5 June 2023. Funding was provided by German research agencies, and the final deliverable is a special‑print book summarising the system concept and experimental findings.