Very Fast Transient Overvoltages Mitigation System

Parallel RLC Resonator Circuit


Switching of Bus-charging currents are common operations in HV substations normally performed by the disconnectors (DS), it consists on the switching operation of an AC voltage source from an unloaded section of busbar and it causes several dielectric breakdowns to occur across the gap during the switching process.

These breakdowns produce the so called Very Fast Transient Overvoltages (VFTO) phenomena that travels towards all of the connected equipment. VFTOs are of special concern in UHV-Gas Insulated Substations because they reach voltages values close or higher than rated Ligthing Impulse Withstand Voltage putting the phase-to-earth insulation systems of the disconnector and adjacent Equipment in jeopardy. VFTOs normally last less than 5us but several hundreds of them are produced at every breaking/making operation.


Available license




  • Cost-Effective
  • Easy to implement
  • Compact and fully compatible with existing GIS


  • UHV-AC Substations
  • Transients Overvoltage Protection for disconnectors
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