In order to protect the safety of 100 Mvar static synchronous compensator (STATCOM)

a complete and reliable protection system must be built. Based on technology innovation and engineering practice of the 35 kV/±200 Mvar cascade STATCOM in China southern power grid

this paper focuses on the protection design of the highvoltage and highcapacity STATCOM in the power system. The power unit protections are classified by the difference in the export strategy

and the converter chain protections are arranged using the external signal source. According to the severity of different faults

three different export strategy of bypass

blocking and tripping should be executed. In consideration of the special operation characteristics of STATCOM

the dual overcurrent protection and 35 kV breaker failure protection are designed

to increase the STATCOM running safety. With the design of power unit online bypass function and converter chain overcurrent blocking restart function

the integration of protection and control is achieved

thereby greatly enhancing the operation reliability of STATCOM. This work is supported by National Key Technologies R&D Program (No. 2007BAA10B02).