Technical Resources for Substation Capacitor Bank Switching.

S&C Electric Company introduced pre-insertion inductors in 1986, and they quickly became the most popular method for controlling transient overvoltages during capacitor-bank energization. Pre-insertion inductors are ideal for limiting inrush current and overvoltage at the capacitor-bank bus, for limiting phase-to-phase switching-surge overvoltages at remote transformers, and for controlling overvoltages on long, open-ended lines and on the user's utilization-voltage bus.

And in the over 40 years that S&C Circuit-Switchers have been the industry-standard capacitor bank switch, S&C engineers have given a number of technical papers and presentations to help in the selection of a capacitor switching device, and in understanding the application of pre-insertion inductors. Here is a selection of S&C’s most popular published resources on S&C Circuit-Switchers and their application as capacitor bank switches:

One of the best resources for selecting the appropriate style of pre-insertion inductor for your application is S&C engineer Ernest Camm’s, Shunt Capacitor Overvoltages and a Reduction Technique, presented at the 1999 IEEE/PES Transmission and Distribution Conference and Exposition in New Orleans, LA.

Two publications, Consideration of the Effect of Pre-insertion Impedances on the Overvoltages produced by the Energization of a Shunt Capacitor Bank and Evaluation of Methods for Controlling the Overvoltages Produced by the Energization of a Shunt Capacitor Bank discuss in detail the mitigating effects of pre-insertion inductors upon phase-to-phase overvoltages at the remote bus of line-length to the remote bus, capacitor bank size, available fault current at the capacitor bank, number of transmission lines connected to the capacitor bank bus, and load connected to the remote bus. And it includes a comparison to pre-insertion resistors and synchronous closing devices. Another great resource on capacitor bank switching is Solving Customer Quality Problems Due to Voltage Magnification. In this paper, S&C Electric Company helps Duke Power identify the possible sources of voltage magnification problems affecting one of their customers and to find an economical solution. A comparative evaluation available capacitor-switching transient mitigation switching devices suggested the use of low-resistance pre-insertion inductors applied with circuit switchers to energize the 100 kV capacitor bank. In a related article, Selecting a Capacitor-Switching Overvoltage Control Method Effective in Preventing Nuisance Tripping of Adjustable-Speed Drives, voltage magnification is discussed as it specifically applies to its impact on the functioning of adjustable speed drives.