The effect of switching surges on 34.5 kV system design and equipment

High failure rates of equipment resulting in severe operational problems caused the Colorado Springs Dept. of Utilities to investigate switching surge phenomena on their 34.5 kV distribution system. Digital simulations were performed to quantify the magnitude of overvoltages created by such operations as cable switching, capacitor bank switching, and switch restrike in an effort to identify the causes of padmount switchgear failures on the underground portions of the system. Results of the study indicated that certain system design changes could be made which would greatly alleviate the severity of the switching surge environment found on the system. The application of arresters was investigated in an effort to further reduce the impact of these transients. Results of field tests and digital simulations confirmed the need for increased BIL levels in switchgear being purchased for this system voltage