Analysis of the Measurements of the Radiated Emission from 9 kHz to 150 kHz from Electric Railways

Abstract

The frequency domain measurement of radiated emissions from electric railways (from 9 kHz up to 150 kHz) has been omitted from the main part of the relevant standard (lack of repeatability and reproducibility of the results is mentioned as the reason). This paper describes the radiated emissions measured from three electric trains to emphasize the importance of the suitable time length selection (by comparing specific durations of the recorded data: 1 min and 5 min) and the influence of calculation methods of the resultant spectrum in frequency domain (RMS, mean, and Max of spectrum). The results revealed the requirement of unique definitions for pre-, during-, and post-measurement factors so that the repeatable and reproducible results could be achieved. The prerequisites for having less uncertain results are as follows: (1) pure background measurement (in energized and de-energized state of the catenary); (2) precoordinated operation mode, speed, and power of the train during the measurement; (3) precise details of the analysis step. A unique analysis method is required (to be clearly elaborated in the relevant standards) to obtain comparable results between different working groups engaged with the radiated-emission measurements from a train in a frequency range of 9 kHz to 150 kHz.