The objectives of this research performed on field-aged cable cross linked polyethylene cable samples, removed from service by DSTAR member utilities, were to:
- Evaluate the linkage between impulse duty and insulation degradation in field-aged cross linked polyethylene primary distribution cable.
- Determine if a recently developed partial discharge site detector can successfully assess cable insulation aging.
The responses of semi-conductive jacketed cable to the following were investigated.
- Impulses originating on the overhead system.
- Lightning ground strokes near the cable trench.
Field tests, augmented by simulation studies, were performed to:
- Characterize voltage transients generated by routine cable and capacitor switching operations.
- Compare the performance provided by different switching devices.
- Generate guidelines for switching practice and arrester application which can minimize switching surge overvoltages applied to underground distribution systems.
Based on extensive field tests, this research had the following objectives:
- Characterize ferroresonant behavior when grounded-wye padmount transformers are switched.
- Develop formulas for estimating ferroresonant overvoltage magnitude as a function of transformer and cable parameters.
- Provide detailed guidelines specifying the maximum cable length which can be switched with a given transformer without exceeding a critical overvoltage magnitude.