ELECTRIC LOCOS.

Poverty Bay Herald, Volume LX, Issue 18203, 26 September 1933, Page 9

ELECTRIC LOCOS.

POWER LINE BEGINS STAFFLESS SUB-STATIONS SMOKELESS TUNNELS “An epoch-marking work” is fclio dos('ri])tion applied 'by the Wellington Post to the electrification of the North Island Main Trunk railway between Wellington and Paekakariki, the construction work on which has been commenced recently.

Power as supplied by the "Public volts, three phase, alternating current rent. But. power as used for traction purposes—'tramways and railways —and for most lifts is direct current. In this case power will be obtained initially from the Public Works Department’s sub-station at Khaitdallah —11,000 volts, three phase, alternating current —and will be transmitted to the rail way sub-stations (live in number, located at selected points along the railway, for transforming into 1500 volts direct current. At Otira and Lyttelton the locomotives received direct current at 1500 volts, and the locomotives to be used here will be ot much the same type. Special interest attaches to the five sub-stations. They will be of the most modern type, using mercury arc rectifiers instead of rotating machinery. The mercury arc rectifiers in question work on much the same principle as the rectifying valve used in wireless apparatus, and have during recent years been developed to a point where they are completely reliable for traction purposes. Installations of this kind have been used in Australia for a number of years and in some of the later electrifications in England. The main control of the switching

and other arrangements will be from one point, and he carried out by the method known as supervisory control. This control, which works somewhat on the principle of tin' selective telephone enables the various functions of any or all of the sub-stations to be carried out by means of push buttons from a central point, thus avoiding tilt' necessity for staff having to 'be in attendance at the sub-stations. The advantages of electrical fraction in the new double-deck tunnels between Wellington and Tawa Plat and in the old simrle-track tunnels on the Paekakariki Hill are obvious.