8.1.2.10 Impact of series compensation on protective IED of adjacent linesSEMOD168320-318 v2Voltage inversion is not characteristic for the buses and IED points closest to theseries compensated line only. It can spread also deeper into the network and thisway influences the selection of protection devices (mostly distance IEDs) onremote ends of lines adjacent to the series compensated circuit, and sometimeseven deeper in the network.en06000616.vsd~~FBEBEAZSAUAA ZLAIAUDDZLBIBUBZSBZLFIF-jXCIEC06000616 V1 EN-USFigure 90: Voltage inversion in series compensated network due to faultcurrent infeedVoltage at the B bus (as shown in figure 90) is calculated for the loss-less systemaccording to the equation below.U U I jX I I j X X I jXB D B LB A B LF C B LB= + ⋅ = +( ) ⋅ −( ) + ⋅EQUATION1911 V2 EN-US (Equation 60)Further development of equation 60 gives the following expressions:U jI X II X XB B LB AB LF C= ⋅ + + ⋅ −( )1EQUATION1912 V2 EN-US (Equation 61)( )01= = ++LBC B LFABXX U XIIEQUATION1913 V1 EN-US (Equation 62)Equation 61 indicates the fact that the infeed current IA increases the apparentvalue of capacitive reactance in system: bigger the infeed of fault current, biggerthe apparent series capacitor in a complete series compensated network. It ispossible to say that equation 62 indicates the deepness of the network to which itwill feel the influence of series compensation through the effect of voltageinversion.It is also obvious that the position of series capacitor on compensated lineinfluences in great extent the deepness of voltage inversion in adjacent system.Line impedance XLF between D bus and the fault becomes equal to zero, if thecapacitor is installed near the bus and the fault appears just behind the capacitor.This may cause the phenomenon of voltage inversion to be expanded very deep1MRK 506 369-UEN B Section 8Impedance protectionLine distance protection REL670 2.2 IEC 181Application manual
