INDUCTIVE INTERFERENCE OF THE SIGNAL AND PROTECTION SYSTEM OF THE NETHERLANDS RAILWAYS BY HIGH VOLTAGE OVERHEAD LINES RUNNING PARALLEL WITH THE RAILWAYS

This report deals with the inductive interference of the signal and protection system of sections of the Netherlands Railways by high voltage overhead lines running parallel with the railways. The signal and protection system of many railway sections in the Netherlands has a 50 Hz ac supply. The 50 Hz currents in the high voltage line running parallel with the railway induce 50 Hz currents in the rails. These parasitic currents can endanger the operation of the signal and protection system of the railway if both the level of the parasitic currents is too high and there is a rail fracture. Based on measurements and calculations it is shown that the amplitude of the parasitic currents in the rails depend upon many factors such as: the distance between the railway and transmission line, the presence of ground wires, the sequence of the phases on the tower when two circuits of the high voltage line have a symmetrical power load and the amplitude of the currents in the high voltage line. Some methods are given which can either decrease the parasitic currents in the rails or eliminate the dangerous influence of these currents on the signal and protection system of the railways.