The New Scheme Discussion Of Grounded Protection For High Voltage Cables-Aerial Line

In the modern society, more and more electric power cables and cable-lines have been applying in the electric power networks. At the same times the problems of relaying protection have discovered. The parameter traits are not steady contrasting with lines'. Especially the parameter traits of zero-order will be changed by the flowing zero order current. So, the design of relaying protection about electric power cables become complex for the above causes. Another reason is that the research of relaying protection about power cables is not mature. Many technology problems of cables relaying protection need be studied in the future. Because the electric traits of cables are not same the lines', the schemes of relaying protection applying in lines are not satisfied for the power cables. The research of relaying protection about electric power cables and cable—lines will bring out many academic meaning and society benefits.The main types and traits of electric power cables in the world are summarized and analyses in the first in the paper. The universal traits, such as impedance traits and the relationship between zero order current and zero order impedance, are set forth. And the main differences between power cables and aerial lines are analyzes. The grounded distance protection and zero order current protection theorys of aerial line is summarized, and the courses of relaying protection set are set forth. The abuses and bugs are analyzes if the traditional relaying protection theory of lines should be applied in the cables or cable-lines.A new auto-adaptive algorithm of grounded distance relaying and zero order current protections of electric power cables is put forwarded. The traits of non-linear relationship between zero order current and zero impedance and distributing parameter model are took into account. The zero order impedance and zero order current on faulted cable point are be calculated by iterative and insert value method. And the faulted points could be identified in the end. The influences of especial electric traits and grounded resistance to relaying protection can be debased. The ability of standing against transition resisdance can reach 30 ohm. It can satisfy with the request of relaying rules. The new algorithm has been validated by ATP modeling and program in MATLAB.