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-Power grids are large complicated networks in use around. An absolute phase value for a particular unknown-phase line at a local site should be identified for the operation and management of a 3-phase distribution network. The phase shift for a specific point in the line, as compared with a phase reference point at a substation, must be within a range of ± 60 o for correct identification. However, the phase shift at a particular point can fluctuate depending on the line constants, transformer wiring method, line length, and line amperage, etc. Conducted in this study is a theoretical formulation for the determination of phase at a specific point in the line, Simulink modeling, and analysis for a distribution network. In particular, through evaluating the effects of unbalanced current loads, the limitations of the present phase identification methods are described.

In this paper, we deal mainly with a class of periodic tridiagonal Toeplitz matrices with perturbed corners. By matrix decomposition with the Sherman–Morrison–Woodbury formula and constructing the corresponding displacement of matrices we derive the formulas on representation of the determinants and inverses of the periodic tridiagonal Toeplitz matrices with perturbed corners of type I in the form of products of Fermat numbers and some initial values. Furthermore, the properties of type II matrix can be also obtained, which benefits from the relation between type I and II matrices. Finally, we propose two algorithms for computing these properties and make some analysis about them to illustrate our theoretical results.

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In the underground MV BPLC systems, the inductive coupler has been mainly used being clamped around the MV power cable. But the high current on the MV power line causes the magnetic saturation of the inductive coupler, so the quality of coupling could be gone down. To solve this problem, we suggest that the neutral line of the underground MV power line can be used for the coupling as a communication medium, and we have newly developed a inductive coupler with loss less than 5dB for the underground MV neutral line and experimentally assessed it. For the purpose of evaluating the coupler, we had constructed the underground MV BPLC test bed that has the 9 repeating points with the 200Mbps class BPLC repeaters. The length of the test bed is about 836 m. It is located in Ansan-city, Korea. We have measured the transmitted signal attenuation and TCP data rate as the factors of the performance evaluation where the TCP data rate means the data rate over TCP layer. The results measured about the existing inductive coupler and the new one have been compared, and the results measured according to the inductive coupling methods included the neutral line coupling method have also compared. As a result, the suggested coupling method and the newly developed inductive coupler have not only the good performance, but also the cost effectiveness because of the fact that there is no magnetic saturation problem and its small size. Therefore, when we consider the cost effective communication infrastructure for Smart Grid, we can say that the underground MV BPLC system is still attractive.