Constant Voltage Transmission

Constant voltage transmission requires adjustable power factor. Advantages. 1. Better service??no variation in voltage. 2. Better protection, due to high reactances. 3. Tendency to use the frequency of 60 cycles. 4. Increased carrying capacity of line. The limit is changed from maximum voltage variation to maximum energy loss, This allows more power to be transmitted or the distance to be increased, without the voltage being raised. 5. Lower total cost for long lines. The saving in cost is greatest for long lines or large networks, large quantities of power, large conductors, and for the frequency of 60 cycles. 6. The method is easy to apply to existing lines. The change can be gradual, and no change is necessary in line construction. Disadvantages. 1. Cost and attendance of additional rotating machinery. 2. Higher total cost for short lines. 3. In order to obtain the greatest economy from constant-voltage operation, the losses must be increased, and the number of separate lines, which are useful as reserves, must be reduced. 4. Tendency of synchronous machinery to drop out of step, and delay in putting load on the line again after shut-down.