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Successful cooperation between NTi Audio and Siemens Germany

The Augsburg site of Siemens Germany is responsible for the technical safety of the Gundremmingen Nuclear Power Plant, the highest-output nuclear power station in Germany. Within a project lasting two years, the alarm system of the whole site was brought up to the latest technical standards. NTi Audio was selected as the partner for the conceptual design and realization of an automatic daily functional check of the alarm system.

(Source: Press information service KGG Gundremmingen)

The challenge
The components to test comprise about 4'000 loudspeakers spread over 250 loudspeaker lines, the corresponding 100 V audio amplifiers, different alarm signal generators as well as several control stations for speech announcements. Many of these components also have backups for redundancy. The daily test is executed at nighttime during regular operations. The goal is to reliably detect defective single loudspeakers, using a minimal test time, in order to be able to test all components within a reasonable time. Also, the test system must be integrated into the existing alarm system without any structural changes to the building.

The concept

The FLEXUS FX100 was selected as the hardware platform for the loudspeaker and signal generator tests. It is able to test loudspeaker lines within a few 100 ms. Also, thanks to its versatile interfaces, it can be easily integrated into existing control systems. In collaboration with the team around project leader Johann Rehlinger from Siemens Augsburg, a simple and robust TCP/IP-based interface was defined for communication between the FX100 software and the Siemens PLC (Programmable Logic Controller). The PLC acts as the master, triggers measurements on the FX100 and receives PASS/FAIL results as well as detailed measurement results. The outcome of all measurements are collected, evaluated and summarized into a daily status report for the service technician in charge.

The implementation
The FX100 measures the impedance response of each loudspeaker line, and compares the result with a previously-gathered reference. The limits for a PASS/FAIL decision are chosen, so that a single defective loudspeaker within a line is reliably detected. The Siemens PLC switches each single loudspeaker line to one of four control centers, each hosting an FX100 device, and then triggers the measurements.
Since there was only a small time window available for the implementation in the nuclear power plant, the complete system was built up at the Siemens site in Augsburg for an extensive test phase. After passing all tests and accreditation by the legal regulator TÜV, the system was integrated and activated in the nuclear power plant in two short stages. NTi Audio is proud to have contributed to increased safety in the Gundremmingen Nuclear Power Plant.