A province in the central China faces the problem of energy shortage, 800kV Mengxi UHVDC project will effectively broaden the energy input channels of the province, enhance energy supply security, and reduce the pressure on coal transportation. This paper analyses the load, power supply and power shortage of a central province, and explored the role of Mengxi UHVDC project played in improving the energy demand in the Central China power grid. By comparing the different access plans to the grid, this paper demonstrated that it’s more appropriate to divide the Mengxi UHVDC into 1000kV and 500kV at the inverter side for consuming the power of UHVDC and protecting the normal power supply.

Ultra-high voltage (UHV) projects are making power system growing lager and resulting in sharp increase of short circuit currents in some area especially in the vicinity of UHV access points. The paper presented the damage of short circuit current increases and common methods to limit fault current. Taking the construction and development of UHV grid in a province of central China as background, the over short circuit currents in 500kV Grid within UHV were showed and several countermeasures including choosing proper UHV access scheme, implementing UHV substation lower voltage bus partition running, installing reactors, optimizing power grid network based on UHV connection point were proposed and then verified by PSASP simulation. The results show those measures are useful to reduce the short circuit current to a reasonable level.