Layer 5 Layer 4 Layer 3 Layer 2 Layer 1 P1,Q1 P2,Q2 P4,Q4 P3,Q3 P6,Q6 Secondary Transformer P5,Q5 P7,Q7 Figure 15. An example of a five-layer distribution network. P and Q denote the real and reactive power flowing from the upstream bus. model. The performance of our solution has been validated on IEEE 13-bus and 37-bus test feeders. The results are depicted in Figures 17 and 18. It can be observed that the proposed model precisely recovers the line impedance of each branch under all test cases. In terms of R, the largest relative errors are less than 0.001%; as for X, the largest relative errors are less than 0.0005%.http://wzy.ece.iastate.edu/Testsystem.html http://wzy.ece.iastate.edu/Testsystem.html