Study On New Principle Of Ground Distance Protection With Strong Ability Of Enduring Fault Resistance

The correct and reliable action of protection relay relates to security and stability of power system. The thesis proposes a new principle of ground distance protection with strong ability of enduring fault resistance. Based on the assumption that the fault path resistance is purely resistive and current distribution factor is real number, fault line impedance is obtained. The performance at different operation condition, the sensitiveness, the characters when power system swings and the application in weak system of the new algorithm are studied in the thesis. EMTDC/PSCAD software simulations show that the novel algorithm is independent of fault inception angle, insensitive with the source-line impedance ratios and able to measure the fault impedance at the condition of different load current and diverse fault resistance. At the same time, the new algorithm is also accurate in un-transposed lines. After the improved DFT algorithm is applied, the new algorithm is not influenced by power system swing.