138kV Switching Station

Utility Design Services was retained to design the replacement of a 138kV circuit switcher and all protection and SCADA control systems at the station.

The switch station sectionalizes and taps a 138kV transmission line to supply a 138kV line to a coal mine substation.  It was desired to retrofit the existing outdoor control panel enclosure with a new pre-wired panel front to minimize cost and outage length.  UDS made field investigations and took measurements to develop a custom fit relay panel to bolt directly into the existing outdoor enclosure.  The single panel includes two SEL 311C relays to provide line protection and SCADA control of the circuit switchers.  An SEL-3530 RTAC serves as the SCADA communications hub.  A GPS satellite clock was utilized to maintain high accuracy time for sequence-of-event recording.  Relays are connected to the RTAC via fiber optic communications.

UDS provided complete control panel design, including bill of materials, panel wiring diagrams, one-line diagram, three-line diagrams and schematics; as well as foundation design for the new circuit switcher.

Project Scope:138kV Substation DWG

  • Circuit switcher foundation
  • Protection and control design
    • One-line
    • Three-lines
    • DC Schematics
    • Panel layout (retrofit)
    • Panel wiring diagrams
    • Field equipment wiring
    • Bill of materials
    • AC/DC panel arrangements
    • SCADA panel design
  • Conduit and cable design
  • Specifications and bid packages
  • Shop drawing reviews