Given an abnormal situation of SV sampling data caused by a SER soft fault in a field merging unit, this paper analyzes the failure mechanism. The concept of a dual data stream is proposed, and an error prevention method of data processing redundancy is adopted to solve the problem of the SV data error. In order to solve the problem of large area voltage loss of control and protection equipment when the bus merging unit is abnormal in an intelligent substation, a redundancy scheme for the unit configuration is proposed. A seamless voltage selection mechanism of a double bus merging unit voltage connecting to a bay merging unit is adopted to solve the problem of voltage loss of abnormal control and protection equipment. It has been fully verified at the project site. This work is supported by the National Natural Science Foundation of China (No. U1804252) and the Research Project of State Grid Jiangsu Electric Power Co., Ltd. (No. J2018041).