State of Art in Cable Screening Measurements

A brief sketch of the underlying physical phenomena is followed by the definition of transfer impedance zT through capacitance normalized through elastance KT and capacitive coupling impedance zF . The coupling equations through a screen as function of these parameters are given and discussed in detail, introducing the concepts of equivalent transfer impedance ZTE cut - off frequency fc and cut- off cable length lc. The definition of screening attenuation as is critically examined. zT, zF and ZTE are considered as primary quantities, defining clearly the quality of a screen, while as should be given as additional information in rated conditions. Different test methods to measure screening effectiveness of cylindrical screens have been evaluated and the wire injection frequency domain has been suggested to become the reference test method of IEC.