High Voltage Disconnector SwitchHV AC Switchgear

Capacitive current switching test for high voltage AIS disconnector switch according to IEC

Upon restrike of the disconnector gap, the restriking current basically has three components:

  1. high-frequency(HF) component (solid line loop).
  2. medium frequency(MF) component (dashed line loop).
  3. power frequency(PF) component (dashed line loop).

These currents determine the thermal energy that is injected into the arc path, the consequent heating of the arc and the ultimate recovery of the gap. Each of these components have their own contribution to thermal processes in terms of amplitude and/or duration: HF(few kA,but very short duration), MF(few hundreds of A, longer duration), PF(few A but long duration)
In figure, the source can be much weaker(LS2>>LS), whereas all other components can be kept identical to the original circuit: CS1≅Cs, CL1≅CL and LS1≅LS. The capacitor Cp1(low impedance for MF current) effectively shunts the (weak) source part of the circuit with its relatively high impedance circuit
In this figure :

  • Us Supply side voltage
  • Cs1 Supply side capacitance
  • Ls2 Test supply side inductance
  • CL1 Load side capacitance
  • Cp1 Test supply side capacitance
  • Lhf Inductance Cs and CL loop
  • Ls1 Short-circuit inductance

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