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Two Sided Earthing Versus one Sided Earthing for Ethernet Cables
Wei Wang1,2,3, Tom Hartman1, Cees Keyer1,2, Jan-Kees van der Ven3
1University of Twente,Enschede, the Netherlands,; 2Amsterdam University of Applied Sciences, Amsterdam, the Netherlands; 3Imtech Marine, Rotterdamn, the Netherlands
The discussion about the earthing method of Shielded Twisted Pair (STP) cables never stopped. There is a difference in opinion between Local Area Network (LAN) equipment manufacturers and Electromagnetic Compatibility (EMC) specialists. LAN equipment manufacturers state that the cable screen should only be earthed on one side of the cable, because it can prevent a ground current loop. EMC specialists advise multi-point earthing, since it is the best way to increase immunity to different kinds of disturbances. To find out which earthing method gives better results, a few measurements are performed. Three kinds of test methods are used: a direct current injection (50 Hz) test, an electric fast transient bursts (EFT-B) test with a capacitive clamp and a continues wave (CW) test using an Electromagnetic (EM) clamp.
The main purpose of our work is to give a global analysis of the electromagnetic coupling problem in a shielded cable. We will go farther than the deterministic approach which is a classic way of solving this problem towards a probabilistic approach, where the excitation is considered as a random variable. In this work, we use the Chaos Polynomial technique to calculate the probability density function of induced voltages. Where the efficiency and rapidity of this technique are dominated comparing to Monte Carlo technique that takes a lot of time.
SNR Kron-Branin Model of Braided Shielded Coaxial Cable under Burst Striking
Christel Cholachue1,2, Blaise Ravelo2
1Federal-Mogul Systems Protection SAS, France; 2Normandy University UNIROUEN ESIGELEC, IRSEEM EA4353
This paper develops a Kron-Branin (KB) model of braided shielded cable wire structures. The structure is assumed to be stroke by kilovolt amplitude high voltage burst. The model is mainly construced with Kron’s graph and Branin’s transmission line (TL). The graph topology of the electrical diagram equivalent
to the initial structure is drawn. The graph consists essentially of branch, mesh, node and cord elements. The tensorial equation transducing the problem under study is reformulated with main unknown the branch currents. The fundamental solutions of the problem are represented by the calculated currents. The analytical expression of the signal-to-noise ratio is established in function of the perturbation strike. A good correlation between analytical expression and simulation is obtained.
Screening effectiveness of unscreened balanced pairs
Bernhard Mund1, Thomas Hähner2, Thomas Schmid3
1bda connectivityGmbH, Germany; 2Nexans France, France; 3Rosenberger HF-Technik, Germany
The screening effectiveness of screened balanced pairs is described by the transfer impedance ZT in the lower frequency range and by the screening attenuation aS and/or the coupling attenuation aC at higher frequencies.
The screening effectiveness of unscreened balanced pairs can be measured in principle with the same test-set-up as for screned balanced pairs as near and far end coupling.
It could be shown, that the screening effectiveness of a single unscreened balanced cable is equal to its unbalance attenuation whereas the screening effectiveness of multiple unscreened pairs, e.g. for data transmission is the sum of its unbalance and the screening effect of the remaining pairs not under test.
At low frequencies, screening effectiveness of unscreened single and multiple balanced pairs can be described and measured as “Low frequency coupling attenuation”