2. R. Nunes, L. Scibile M. Bätz Protection Electromagnétique pour les Alarmes de Niveau 3

3. Introduction n Spurious alarms during BA6 fire n Analysis of AL3 due to electrical power cuts or perturbations n Re-engineering of the hardwired alarm transmission

4. Alarm Analysis n 4 events analysed n Only false hardwired alarms found n Zones BA4, BA5, SY8, Zone 9-Prevessin n Similar analysis shortly after future events

5. Re-Engineering Hardwired Alarm Transmission n Avoid AL3 due to electromagnetic induction n Factor 1: imperfect shielding & grounding of cables and the hardware-triggering unit n Factor2: absence of an input filter on the hardware-triggering unit

6. Actions & Costs

7. Planning n Completed –analysis –design of the filters –planning shielding & grounding n Foreseen –Testing and installation of the filters week 16 to 18 –installation of data logger on most sensitive spots: week 17 –Revision shielding & grounding to be finished July 2002

8. Conclusion n So far, only electromagnetic induction found as a problem n Implementation of the re-engineering under way n Revision of instruction TCR and SCR under way n Regular alarm analysis programmed fur the future