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Förslaget inkom 2004-05-10

Measurements of shielding effectiveness of communication tower cables

OBS! ANSÖKNINGSTIDEN FÖR DETTA EXJOBB HAR LÖPT UT.
Shielded cables are used to reduce radiated interference and to protect electronic components from the effects of disturbing electromagnetic fields. The quality of the shield varies with their design.
To evaluate the quality of the cable shield the shielding effectives has to be measured. This can be done by injecting a current or voltage to the cable shield and measuring the induced voltage or current at the cable conductors. These measurements can be performed in frequency domain or in time domain. Also the test signal amplitude might influence the results.

In this work the measurements shall be performed on two types of cables using frequency domain methods and time domain methods with different amplitudes. The measurements will also include tests in high voltage laboratory. The results of both measurements shall then be compared and a model for shielding effectiveness for those cables, applicable for high voltages and currents during a lightning strike shall be proposed. Based on the measured results a suitable surge protection shall be designed to limit the overvoltages to specified limits.

The tasks to perform:
· Literature survey of the existing techniques for measuring shielding effectiveness
· Time domain measurements using cable generator
· Frequency domain measurements using spectrum analyser
· Time domain measurements using standard current surges (8/20 µs, 10/350 ms up to 15 kA)
· Model for the cables
· Design of appropriate surge protection and its verification
· Final report

The work shall be performed at Division for Electricity and Lightning Research, Department of Engineering Sciences, Uppsala University and will be in cooperation with Ericsson Network Technologies AB.


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