Line protection based on the differential equation algorithm using mutual coupling

The application of the distance protection for distribution systems is increasingly more frequent. However, the distance relaying algorithms employed are designed for single lines without considering mutual coupling between parallel lines. Mutual coupling affects the accuracy of the results. In this work, the behavior of the conventional differential equation algorithm (DEA) is analyzed for its accuracy in the estimation of the fault distance. The response time, the variation of the line parameters, the fault inception angle, the presence of erroneous samples and the mutual coupling are considered in the study. These results are compared with those obtained using the Fourier algorithm. In both algorithms, the errors are significant when mutual coupling is present, reaching 12.59% for fault at the end of the line. In this paper, a new distance relaying called DEA with mutual coupling (DEAMC) has been presented. The new algorithm is an improvement to the DEA algorithm that takes into account the coupling effect in the analytical equations. The DEAMC response has been compared with the conventional algorithms results. The results show that the new algorithm improves the accuracy when mutual coupling is present. The DEAMC algorithm reduces the error to 1.93% for fault at the end of the line.