Topologic analysis on effect of UHV long connections on energy transmittability of power grid

This paper presents a topologic method to analyze effect of UHV long-distance interconnecting lines (long connections) on transmittability of energy in a large-scale power grid. First, the presented method gives a general graph model to show topologic features of power grid with/without long connections. Then, it introduces a concept called transmitting admittance to measure the average transmittability of energy in power grid globally and locally based on the Thevenin's equivalent admittance between each "plant-load" pair. Simulations show power grid with even a small number of long connections has high transmitting admittance so that power flow can be transferred efficiently both globally and locally, while the transmission ability is almost independent of the system scale. Conclusions are also confirmed by statistical data from IEEE systems and some actual power grids. Thus, long connections are necessary in power system topologically on improving the global transmittability of energy.