Multi-Function Controller PFVL141C-50,0MN 3BSE024994R5000

Multi-Function Controller PFVL141C-50,0MN 3BSE024994R5000

Multi-Function Controller PFVL141C-50,0MN 3BSE024994R5000

It is a common practice to call this phenomenon current inversion. Its consequences on operation of different protections in series compensated networks depend on their operating principle.

The most known effect has current inversion on operation of distance IEDs (as shown in section “Distance protection” for more details), which cannot be used for the protection of series compensated lines with possible current inversion. Equation 73 shows also big dependence of possible current inversion on series compensated lines on location of series capacitors. XL1 = 0 for faults just behind the capacitor when located at line IED and only the source impedance prevents current inversion.

Current inversion has been considered for many years only a theoretical possibility due to relatively low values of source impedances (big power plants) compared to the capacitor reactance. The possibility for current inversion in modern networks is increasing and must be studied carefully during system preparatory studies. The current inversion phenomenon should not be studied only for the purposes of protection devices measuring phase currents. Directional comparison protections, based on residual (zero sequence) and negative sequence currents should be considered in studies as well.

Current inversion in zero sequence systems with low zero sequence source impedance (a number of power transformers connected in parallel) must be considered as practical possibility in many modern networks.