Outdoor telecommunications networks typically have cable lengths of 300 m and more. Sometimes communication lines may even have a total cable length of several kilometers. The corresponding test impulse given by the applicable standard shows the typical waveform 10/700 μs – 5/320 μs as this waveshape is the most representative of actual surges encountered in the field. Coupling via arrestors is the preferred coupling method for unshielded outdoor symmetrical communication lines. The coupling network also has the task of splitting the surge current into multiple pairs in multiconductor cables.
The Haefely TW 8 Telecom Wave Impulse Module is the extension of your AXOS8 Immunity Test System if Telecom Surge Immunity Tests according to IEC/EN 61000-4-5 Ed. 3.0 need to be performed. When external TW 8 (Figure 9-3) module is connected it gets automatically indicated via the link cable (intelligent input). In the front view are three different coupling impedances (1 x 15 Ohm (HI-COM), 4 x 40 Ohm, 4 x 40 Ohm gas arrestors) options. The user selects on the coupling unit (TW 8 module) which impedance is required for the particular application.