Sometime back my team undergone a major maintenance project where several hundred meters of UHV (Ultra High Voltage) and EHV (Extra High Voltage) Transmission Lines were replaced due to insulation breakdowns which led to voltage fluctuations, power outages, and other safety, environmental, and economical risks and hazards. For this case the possible cause of the insulation breakdown is a combination of; 1. Electrical Overstress 2. Thermal Aging 3. Moisture Ingress Other cases can be caused by; 1. Mechanical damage 2. Manufacturing defect 3.Chemical degradation 4. Environmental factors For those who have faced a similar experience, please share your possible cause of insulation breakdown and effects on your system. Below is a section of a defected 600mm^2 UHV transmission line being pulled out of a cable trench.
Un balance load on each phase could be one factor....
Engineering Professional | GIEPNG #7201
11mo1C Cu XLPE x 500A Rating for 800kVA Caterpillar Engine Overhaul.