The voltage of the transmitting generator must lead that of the receiving generator. It follows from Equation 10.1 that the maximum transmitted power will correspond to δ = π/2. The power flux may be regulated by the following basic means:

• Variation in the impedance X • Variation in U1 and U2 • Variation in δ

The traditional methods are as follows:

• Compensation of the reactive power by connecting switched reactors or capacitors in parallel with the load

• Compensation by connecting capacitors in series in the line • Introducing phase shifters, which permit adjustment of δ and hence

control of the power flux Reactive-power compensation The creation of thyristors was the first stage in the development of power electronics, associated with considerable improvement in our ability to control power transmission in ac grids. On the basis of thyristors, highspeed switches and controllers have been created. Figure 10.2a shows a parallel compensation circuit based on capacitors and a thyristor-controlled reactor (Rozanov, 2010).