Transients in EHVDC Power Systems: Part I - Rectifier Fault Currents

This paper presents a concise summary of results obtained from a rigorous analysis of the factors influencing the transient fault currents in an EHV rectifier terminal for a fault on the line side of the dc series reactor. The effect of the exact instant of fault occurrence after the time of completion of a commutation is shown to have special significance. It is also shown that the maximum transient peak currents, even for an "instantaneous" control system, may be on the order of 2.0 times nornal or more for representative dc series inductances when initial load is considered. For a less ideal or slower control system, greater maximum peak transient fault currents are found. Furthermore, saturation of the dc series reactor is shown to result in larger currents. Results for two and three bridges in series, as well as for a single bridge, are given in curve form for convenience of the user.