Preventive fire protection: A danger foreseen is a danger avoided

Since February 2018, a listed heritage villa in Hamburg has been the home of a modern daycare facility. Shortly before it was handed over to the owners, an alarm was set off just in time by the AFDD because of a dangerous defect in the villa’s electrical installation.

Built in 1868 as the summer residence of the Hamburg merchant Wilhelm Amsinck, the historical Amsinck Villa in Hamburg-Lokstedt was recently restored to its previous glory – and offers plenty of space for a modern daycare center. 

 

For a long time, the landmark building had fallen into disuse and had nearly become a ruin. After a complete renovation, since the spring of 2018 the building has assumed its former glory – the result of a joint project by the Rudolf Ballin Foundation, an independent provider of child and youth services, and SAGA, the municipal housing company. 

The complete electrical and safety engineering was the responsibility of the Hamburg specialist Gerhard Köpke Elektromontagen GmbH, which commissioned ASE Schaltanlagenbau Ströhl GmbH of Ahrensburg as the control cabinet manufacturer.

The special challenges of historical buildings

Whether a period staircase or original wall decorations: during the renovation work many of the period furnishings of the villa were to be preserved as valuable elements of the building. This posed enormous technical challenges, especially for the electrical installation: “For example, we couldn’t lay cables in the walls, only in the floor or in the old chimney shafts,” said project manager Oliver Steinfath of Köpke Elektromontagen and gave a specific example: “For the supply line to an emergency luminaire, our fitter even had to climb through the roof truss quite acrobatically.” In such an environment, subsequent corrections are only possible with considerable effort.

Alarm goes off just before handover

Shortly before handover, a fault was detected in the electrical system: An arc fault detection device (AFDD) in one of the sub-distributions tripped reproducibly, clearly indicating the line was faulty. “We were pretty worried about that for a moment,” admits Oliver Steinfath. However, proper functioning of the switch allowed a supply line to the outdoor lighting to be clearly identified as the affected circuit and the fault was located and rectified: during renovation a tiger saw had damaged a line in a cavity wall that was no longer accessible. 

 

“In this case, a conventional miniature circuit breaker would not have tripped at all,” said electrical engineering expert Steinfath. Although miniature circuit breakers offer protection against short circuits and overloads, a dangerous arc fault had occurred where the line was damaged. This could have caused temperatures of several thousand degrees at a single point. Electricity is one of the most frequent causes of fires, almost 30% of which are caused by defects in electrical installation, anywhere from the distribution board to the socket outlet.

DIN VDE 0100-420 requires arc fault detection devices (AFDD)

Safeguards against arc faults and related fires must be reliably in place not only during construction but even more importantly during regular daycare center operations. The current DIN VDE 0100-420, for which the transition period expired on December 19, 2017, also addresses this. Since then, arc fault detection devices (AFDD) have been prescribed as a “recognized technical rule” for many application areas. As laid down in this standard, arc fault detection devices (AFDD) are also mandatory in bedrooms or lounge areas of daycare centers and of elderly care homes. “Consequently, there was of course no question for us and our clients that we would use appropriate protective components,” says project manager Oliver Steinfath. “We could therefore be sure we were on the safe side.”

Villa with comprehensive protection concept

Around 30 arc fault detection devices (AFDD) are in operation in the Amsinck Villa. In particular, they protect all sockets and other circuits in all bedrooms and social rooms in compliance with standards. The protection components are available for rated currents up to 16A and 40A. The devices offer simplified handling and enable around 300 possible combinations with other protective devices such as RCBOs. Both the 16A and 40A versions feature an LED multi-function button which can also be used to easily perform a mechanical test function. Triggering is indicated by the LED multifunction button jumping out. The LED lights up red in the operating state. In the event of a fault it flashes yellow, red, or yellow/red.

In this case, a conventional miniature circuit breaker would not have tripped at all.
Oliver Steinfath, Project Manager, Köpke Elektromontagen GmbH

In the Amsinck Villa, the arc fault detection devices (AFDD) complement the residual current operated circuit breakers, RCCB/RCBO combinations, and miniature circuit breakers also supplied by Siemens, to form an integrated protection concept for perfect and standard-compliant all-round protection for people, systems, and goods and for the best fire prevention. This assessment was also confirmed by the TÜV Nord certification body, which tested and accepted the entire electrical installation in the Amsinck Villa. Even after their first practical test, the Siemens arc fault detection devices (AFDD) continue to work perfectly. Fortunately, they have not been needed again.

2018-09-10

Picture credits: Siemens AG/W. Geyer/O. Steinfath

The arc-fault detection devices (AFDD) are part of Siemens’s standardized Sentron portfolio. The technical basis of the arc fault detection devices is the SIARC detection technology patented by Siemens: The devices continuously measure the intensity and duration of episodes of high-frequency (HF) noise associated with the voltage and current and the gaps between them. An integrated microcontroller analyzes these signals and triggers disconnection of the connected circuit within a fraction of a second if anything unusual is detected.

 

With the 5SV6 arc fault detection device (AFDD), Siemens is the first manufacturer to present its latest innovation, the third product generation for preventive fire protection: The 5SV6 AFDD is the first device on the IEC market with integrated miniature circuit breaker in just one modular width (instead of the previous 2 modular widths). Because of its very narrow design, the switch can be installed in distribution systems offering little space. In new electrical installations, this saves 50%of the space compared to installing two separate devices.

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