High-Voltage Overhead Line Breakage Protection Based on Voltage Waveform Correlation

High-voltage overhead line is prone to the break fault due to external forces and lightning strikes. The live line is likely to cause personal injury and death after landing. However, the existing line protection device can only remove the faulty line after the broken line is grounded. A new principle of high voltage overhead line breakage protection based on voltage waveform correlation is proposed. Based on the R-L model of transmission line, the new principle uses the transient voltage information at both ends of the line to calculate the Measured Voltage Difference (MVD) of each phase of the line; and uses the uniform transmission line impedance matrix and the transient current information at both ends of the line to calculate the Calculated Voltage Difference (CVD) of each phase of the line. The waveform correlation coefficient is introduced to measure the correlation degree between MVD and CVD. When there is no fault in line, CVD is almost equal to MVD and the correlation coefficient is close to one. If an internal fault occurs on the line, the correlation coefficient will reduce. After an internal fault is identified, the currents of the two ends are adopted to distinguish the break fault from short-circuit fault of the line. A three-machine nine nodes model is established in PSCAD/EMTDC and the simulation results show that the proposed protection can reliably identify the break fault in different load conditions and different lengths.