Analysis and Solution of Frequent Start-up of Incremental Differential Protection

In this paper, it is analyzed that the reason of frequent start-up of incremental differential protection is caused by double SC capacitor banks in a converter station. No abnormality was found in the secondary circuit of CT. In the process of inspection, it is found that the accuracy adjustment coefficient of 010A converter protection device 2 does not need to be adjusted, and the accuracy meets the error requirement. The accuracy adjustment coefficient of 010B converter protection device 2 can meet the error requirement only after individual adjustment. However, one year later, when the substation was out of service, it was found that the accuracy adjustment coefficient of the individual channels of 010B converter and rheological protection device 2 was quite different. Because the accuracy error of the external circuit meets the requirement, it is confirmed that the acquisition circuit of 010B converter protection device 2 is abnormal. Therefore, the acquisition circuit of 010B converter protection device 2 is replaced, including AC input circuit and sampling and holding circuit. After replacement, double SC capacitor banks were put into operation many times, and no start-up phenomenon occurred. In view of this incident, this paper also proposes two optimization schemes. One is to enhance the anti-interference measures of AC input plug-in of converter protection device. Secondly, dual redundancy is used in differential channel of single CPU plug-in.