Voltage Regulation and Insulation for Large Power Long Distance Transmission Systems

Heretofore the distance to which power could be transmitted has been limited. This limitation is now removed by a simple method of loading the line with synchronous condensers, so that the current and voltage may be kept practically in phase. High power factor and hence high efficiency result, and the voltage rises of the system are very much reduced, thus reducing insulation strains. A standard frequency of 60 cycles is advocated for the national system, and 220,000 volts is proposed as standard for extra large-power, long-distance transmission. The system of regulation proposed will result in practically constant voltage at all points of the line at all loads. And power may be taken from or supplied to the line at any point, and the power over sections of the line or over the entire line may be reversed and the constant voltage system maintained. A simple diagram is given, and this shows that for a 60-cycle, 220,000-volt line, the line-charging current supplies the capacity current required for about 0.8 load or 320 amperes load current, and that for larger loads the synchronous condensers supply leading and for smaller loads lagging current. Thus it is seen that the transmission line has largely inherently the currents required for self-regulation, if we correct initially the power factor of the loads to near unity. Every induction motor added to the power system calls for a certain capacity current for correction of power factor to reduce the losses from motor through to the power station.