Cable Installation Limits in Earth Fault Compensated 110-kV-Networks

Forced use of cables in earth fault compensated networks increases the capacitances to ground in the grid so that the capacitive ground fault current ICE increases, which causes problems concerning arc extinction. The ground fault current (limited to 132 A due to standards in Austria) depends on detuning, damping, unbalance, harmonics, saturation, operating voltage, harmonic resonances, and the distribution of the line inductances and capacitances (within the grid). A new grid calculation program was developed by TU Graz which allows to calculate the expansion limits of earth fault compensated networks under consideration of the harmonic contents in the fault current. Concerning the determination of these limits existing formulae are adequately adapted. The calculated results have been verified in real network experiments. Technical measures for further operation of the grids are investigated