Ferranti effect

The effect of p.f. can be controlled by shunt capacitors, near the load point and the Ferranti effect by altering the line parameters. Since... 

Generally, an HT distribution network has a very short length (f), less than 10-15 km. Moreover, the leakage capacitance (C ) for system voltages up to 66 kV is almost negligible. The Ferranti effect is therefore not applicable to a distribution network. 

For the same system frequency, the Ferranti effect can be reduced by... 

This product can be reduced by reducing X, using series capacitance with a reactance X, which will reduce to - Xq. This is where reactive control plays a major role. By meticulous reactive power manage-ment, the Ferranti effect can be controlled and the electrical line length increased to the desired level. It is a different matter that the electrieal length of the line cannot be raised infinitely, for reasons of stability, as discussed later. 

To apply the corrective measures to limit the Ferranti effect it is essential to first study its over voltage (OV) status at the far end of the line. Consider the earlier system TZ of 400 kV 50 Hz and draw a voltage profile as illustrated in Figure 24.17, for the voltages worked out as in equation (24.7), at different lengths of the line. The voltages, for the sake of simplicity, are also shown in Table 24.4. 

Table 24.4 Far-end voltage, due to the Ferranti effect, in a 400 kV TZ type line, at different line lengths...

Figure 24.17 Voltage profile of a 400 kV/400 km radial line on a no-load illustrating the Ferranti effect...

Line length effect or Ferranti effect, sin 6, that will determine the optimum line length which will also depend upon whether it is a radial or a symmetrical line. 

Ey = phase voltage at the transmiliing-end Vy = phase voltage at the receiving-end By = line length effect or Ferranti effect at the end of the line, in degrees /i = load current P-JQ Vj... 

There is no leakage capacitance, Co, and hence no Ferranti effect on such low voltages. We will use series compensation to reduce the line voltage drop and improve the regulation and hence the stability of the network as well as its load transfer capability,... 

---