Contact Defects Diagnosis and Load Capacity Estimation for Double-Fracture Disconnect Switchgear

At present, there is no effective ways to estimate the contact status and maximum load capacity of the double-fracture disconnect switchgear (DDS), which cause the contact defects cannot be excavated when the load is low. To this end, the heat transfer process inside the DDS is analyzed using a thermal network, and a varying-parameters state-space model is established, which takes the load current and ambient temperature as input variables, and key nodes temperature as state variables. On this basis, a real-time least square system estimation method for contact resistance is proposed, whose input are the on-line measurement results of contact temperature, shell temperature and load current. Then, an estimation method for maximum load capacity is proposed according to the estimated contact resistance and rated temperature rise. A DDS temperature rise experiment plat-form which takes a switchgear cabinet as an example is set up to verify the accuracy of the state-space model and the effectiveness of the contact resistance estimation under different contact resistance. The proposed method can diagnose the contact defect of the two contacts of DDS and estimate its maximum load capacity without any additional hardware, which provides timely guide for substation operation personnel and builds the physical layer, model layer and application layer of DDS digital twin.