In recent years, the effects of electromagnetic fields on the human body and electronic appliances have become a matter of great social concern, and international organizations have already issued guidelines and standards on the matter. At railway substations, the load fluctuates significantly over time depending on the status in terms of EMU operation, powering or application of regenerative braking, and track layouts have become increasingly complicated. These have given additional food for thought.

In this context, the RTRI evaluated electromagnetic fields generated at railway substations through theoretical calculation. This process revealed that the major source of electromagnetic fields was contact wires, prompting the RTRI to establish a technique to calculate the electromagnetic field generated by such wires. By applying this method, the RTRI calculated the electromagnetic field generated around substations and compared it with measured values. The results indicated that the error in the magnetic field was about 10%, and the calculated and measured values of electric fields were in the same order.

The RTRI discussed measures to effectively reduce the electromagnetic field by applying this method of calculation. Figure 1 shows the AC magnetic field generated when the layout of contact wires connected to the rectifier output terminals of a DC railway substation was changed; the values have been calculated and represented in 0.5-m square meshes. It is estimated that a negative DC bus laid between two positive DC buses cuts the generated magnetic field to about one third of that under a normal contact wire layout (Fig. 1).

This technique enables the estimation of the electromagnetic fields generated at the design stage by substations, the evaluation of measures to reduce such fields in quantitative terms, and moreover the determination of the layout for contact wires at substations according to electromagnetic field limits set forth in international guidelines or standards.