NS measuring system

In the past we developed a general grounding concept, which simultaneously ensures safety of persons and equipment against threats posed by power short circuits, lightning, and other intense disturbances. Part of our effort is directed to implement this concept on a large scale in NL, in the power, phone and CTV grids.

To do this we started cooperations with NUON ('97) and NS ('98) in contracts which span several years.The NS introduces a 25 kV a.c. power traction system. In the design of this power system and its associated grounding, HRc tried to minimize the coupling to and from the environment at 50 Hz, at harmonics and of switching phenomena.

The need for a very careful design was clearly established during '98 measurements which we carried out together with HRc in Luxembourg; there up to 35 percent of the traction current returned via the earth. These results have been presented at the Berlin and Tokyo railway conferences and at the COST 261 workshop in Oostende. The first 15 km of the Havenspoorlijn near Rotterdam will be a pilot project in NL.

We designed a broadband (50 Hz - 1 MHz) 250 channel system to simultaneously measure the currents through all conductors and relevant voltages at seven places distributed along the Havenspoorlijn. We built the prototypes of the sensors and the signal converters. A number of companies is involved in the construction of the total system. NLR takes care of continuous data registration below 500 Hz, EHC will capture data also above that frequency.

Other participants are NS-TO and NS-ME. The measurements will be performed under another contract with NS-RIB in two campaigns of several months medio and end 2000. Scientific publication of the results has been formally agreed by NS-RIB, but is not envisaged before 2001. As part of this research we determined the coefficients (50 Hz and up) of the many conductor transmission line formed by the Botlek tunnel railway system. The BEM software by IES had to be adapted for this. Minor deviations with respect to Carson's approach were found. A report has been finished and accepted by HRc; the report has been written as journal paper.