The 35kV bus surge arrester burned out

A 35kV busbar surge arrester can burn out due to internal dielectric failure, thermal runaway of MOV elements, moisture ingress, or installation-related issues.Common Causes of Surge Arrester Failure1. Thermal Runaway of MOVs: Surge arresters use metal oxide varistors (MOVs) to divert overvoltages. Each surge generates heat in the MOV discs, and if the heat is not dissipated efficiently, it can cause thermal runaway, leading to cracking, melting, and complete failure of the arrester . 2. Moisture Ingress: Water can penetrate the arrester housing through aged seals, cracks, or diaphragm defects. Temperature-induced pressure changes draw moisture inside, causing condensation that corrodes MOV discs and conductors. This increases resistive leakage current and can trigger internal breakdown . 3. Temporary Overvoltages (TOVs): System events such as ground faults, switching surges, or unbalanced loads can create voltages above the arrester's rating. Sustained overvoltage forces the MOVs to conduct continuously, generating excessive heat and potentially causing flashover or dielectric failure . 4. Installation and Busbar Issues: Poor installation, such as loose connections or improper conductor contact, can lead to overheating at busbar terminals, which may propagate to the surge arrester. In 35kV systems, even minor installation errors can compromise insulation and trigger arrester burnout .Diagnostic StepsVisual Inspection: Look for discoloration, bulging, or white powdery residues on the arrester or busbar, which indicate overheating or dielectric breakdown .Leakage Current Monitoring: Measure resistive leakage current under normal voltage. A steady increase signals internal moisture or MOV degradation .Infrared Thermography: Detect hot spots on the arrester or busbar to identify abnormal heating before catastrophic failure .Insulation Testing: Use a megohmmeter to check busbar insulation resistance. Low readings indicate compromised insulation that may have contributed to arrester burnout .Preventive MeasuresCondition-Based Maintenance: Implement real-time monitoring of leakage current and temperature to detect early signs of degradation .Regular Thermal Scans: Use infrared cameras during routine inspections to identify overheating units .Proper Installation: Ensure strict adherence to manufacturer installation manuals, including secure conductor connections and correct torque on terminals .Environmental Protection: In humid or polluted environments, use polymeric or sealed arresters and maintain housing integrity to prevent moisture ingress .SummaryA 35kV busbar surge arrester burns out primarily due to internal MOV overheating, moisture ingress, overvoltage stress, or installation defects. Early detection through leakage current monitoring, thermal imaging, and insulation testing is critical. Preventive strategies include condition-based maintenance, proper installation, and environmental protection to extend arrester life and ensure reliable busbar operation.