Experiments on the susceptibility of the direct digital control system to EMP in intelligent buildings

Direct digital control (DDC) systems now play an important role in intelligent control of modern buildings. The susceptibility of these control systems to the pulsed electromagnetic environment is studied. A model of a DDC system consisting of computer, communication line and digital controller was tested in a HEMP simulator and a pulsed magnetic field simulator. We measured the interference thresholds of the computer and the DDC controller as well as the coupling of the outside field to the shielded twisted lines. The communication line was found to be the main path that causes interference in the DDC. Protection approaches, which can greatly reduce the sensitivity of the system to EMP interference, were also developed for the system.