Measurement Techniques for Electromagnetic Shielding Behavior of Braided-Shield Power Cables: An Overview and Comparative Study

Abstract

More and more EMC tests have shown that the radiated emission problems of the equipment under test mainly concentrate on the intercon- nected power cables and cable connectors. Measurement of shielding performance is a prerequisite for quantitative and qualitative evaluation of the frequency-dependent characteristic of braided-shield power cables and cable connectors. Due to the asymmetric geometric structures of these cable assemblies, compared with the coaxial and symmetrical communication cables, the commonly used transfer impedance testing methods may not be suitable. In view of this, several improved simple and effective measurement methods, including transfer impedance and shield reduction factor testing methods, were proposed in recent years. These methods, based on the equivalent circuit model of the characteristic parameters, provide good repeatability for the measurement of shielding performance. This paper presents an overview analysis of various measurement techniques for shielding performance of power cables and cable connectors, highlights some of its equivalence principle in measurement setups, and showcases a brief comparison between transfer impedance and shield reduction factor.

Electromagnetic Shielding Performance Measurement for Braided-Shield Power Cables at Low Frequency Regimes

“…From a practical point of view, d → 0 in (7) can be used to describe the self inductance L loop for the case of braidedshield power cables placed on the surface of the ground. As for the others, i.e., a single-braid, with an outer diameter in the 5-15 mm range, at a height of 50-500 mm above ground, the average value of L loop is about 0.955 µH/m [6].…”

“…In general, either transfer impedance (Z t ) or shield reduction factor (K r ) is the characteristic parameter used to analyze electromagnetic shielding performance of the cables, and Z t or K r can be approximated by analytical formulas [4]- [7]. According to the definitions, transfer impedance and shield re-duction factor are all positively correlated with the shielding performance, i.e., the smaller Z t or K r is, the better shielding performance of the cable will be.…”

“…Shield reduction factor K r , compared with transfer impedance Z t , can provide more intuitive evaluation of electromagnetic shielding performance of braided-shield cables at low frequency (typically below 1 MHz) [7]. In [13], a flux density probe has been used for the measurement of K r at 50 Hz, and obviously this is the most direct way to assess the shielding performance for several specific frequency points.…”

“…In this paper, which is an extension of the investigation presented in [7], we highlight the shield reduction factor method (SRFM) and the equivalence principle for the shielding performance assessment of braided-shield power cables to improve the test cell which can be suitable for the measurement of gain (T/R) parameters from 25 Hz to 1 MHz, and finally provide intuitive evaluation for the shielding performance of CUT. This paper is structured as follows.…”

“…This paper is structured as follows. Section 2 presents the generalized definition of shield the reduction factor, and corresponding implementation of SRFM for the measurements as an extension of the work in [7]. Section 3 shows results for shielding performance of CUT evaluated by shield reduction factor as well as transfer impedance, and also showcases a detailed comparative discussion.…”