Tridonic | Smart Lighting | Apr 30, 2026

Historic Luminaires Ready for the Smart City

Cities want to preserve historic luminaire designs while at the same time using them as smart, digital infrastructure. Against this backdrop, the new Edition 4 of the industry standard Zhaga Book 18 extends the Zhaga D4i ecosystem to include decorative outdoor luminaires. Tridonic supports this step technologically: the new D4i LED driver portfolio integrates the surge protection that is now mandatory. This provides luminaire manufacturers with a standards compliant and installation friendly basis for making classic designs fit for the smart city.

With traditional street luminaires, for example in the “cobra head” form factor, sensors and communication nodes can be mounted directly on the surfaces of the luminaire head. In this case, the DALI bus does not leave the luminaire head.

With decorative and historic luminaires, however, mounting sensors and communication nodes on the luminaire head is often either structurally impossible or aesthetically undesirable. Edition 4 of Zhaga Book 18 therefore specifies requirements for so‑called “bracket‑ready luminaires.” In this concept, a mechanical module (bracket) with up to two Zhaga sockets can be installed separately on the pole. Due to architectural constraints, the DALI bus must leave the luminaire head in order to connect to the bracket. The long cables inside the luminaire pole carry the risk that voltage surges on the supply lines are coupled into the communication lines, potentially damaging the connected D4i circuits.

Standards‑compliant safety through integrated surge protection

To ensure system reliability and prevent failures, Zhaga Book 18 Edition 4 mandates surge protection for the communication system. In addition to an SPD (surge protection device) in the pole‑mounted bracket to protect the inserted sensors, an SPD must also be implemented in the luminaire head to protect the D4i bus.

Luminaire manufacturers therefore face a choice: either they install a separate SPD that complies with DALI Part 152, or they use control gear that already integrates surge protection in accordance with DALI Part 151.

Tridonic significantly simplifies luminaire design for manufacturers. LED drivers in the SNC portfolio come with the required surge protection in accordance with DALI Part 151 integrated as standard. This eliminates the need to accommodate a separate SPD in the often very limited space inside the head of historic luminaire designs. The integrated solution ensures that luminaires meet the requirements of Zhaga certification for “bracket‑ready luminaires” right from the outset. Manufacturers avoid complex mechanical designs, reduce wiring complexity, and minimize potential sources of error during installation.

“Cities are faced with the challenge of preserving their historic identity while at the same time building a future‑proof, digital lighting infrastructure,” explains Barbara Fritsch, Product Manager Outdoor at Tridonic. “With our drivers featuring integrated surge protection, the complexity of luminaire design is reduced, allowing our partners to fully concentrate on the design and scaling of their smart city solutions.”