Interaction And Impact Of Geomagnetically Induced Current In Different Voltage Level Power Systems

Considering the factors affecting geomagnetically induced currents (GIC) and the parameter characteristics of different voltage level systems, previous studies of GIC in multi-voltage networks mainly concentrated on the highest voltage level and ignored secondary voltage levels. With the construction of UHVAC power grid, the 1 OOOkV network has been added into the China’s power system, and the 750kV power network gradually becomes the main power network in Northwest China. Taking the parameters of transmission lines, transformer types and other factors affecting GIC into consideration comprehensively, the estimated GIC levels are high in secondary voltage level networks, such as 500kV and 330kV. GIC in the secondary and highest voltage level networks will interact with each other through autotransfonners. Modelling and calculation methods for multi-voltage level networks have been presented in previous literature. Therefore, figuring out the interaction and the flowing mechanism of GIC in different voltage level systems and studying on the characteristics of the interaction is significant for accurately calculating GIC in EHV and UHV systems.Based on the North China-Central China-East China Power Grids (Sanhua Gird) and Gansu province power grid, using "Full-node model" and the nodal admittance matrix method, GIC in single-voltage grids only containing the highest or secondary voltage level and dual-voltage grids containing the highest and secondary voltage levels are modeled and calculated. Then the interaction between GIC in 500kV network and 1 OOOkV network is analyzed, and the same method is applied to a 330kV and 750kV system. This is the first time that the GIC interaction between different voltage levels is examined, as well as its impact. And GIC risks in the UHV and EHV systems are assessed by comparing calculated GIC data with monitored values of GIC. Finally, a study based on a simple and reasonable network model is presented, and results show the mechanism and regular pattern of interaction of GIC in multi-voltage level systems.