Alexandra Substation: Upgrade of existing substation to 180MVA firm capacity88/11kV substation to 90 MVA Firm Capacity


Client: City Power
Date: January 2010 – July 2012

The Alexandra Substation previously consisted of two outdoor 45 MVA transformers, which were directly fed by incoming HV lines. The two existing transformers had firewalls between them but no oil catchment facilities.

The upgrading of the substation consisted of the following:

  • The installation of a third 45 MVA transformer and a fourth transformer bay (for the next phase).
  • The expansion of the existing substation yard towards the south, to accommodate a new control room.
  • The construction of bund walls around the existing and new transformer bays.
  • The construction of a single 88kV busbar.

Scope of work completed

Civil Work:

  • Platform Construction (Bulk Earthwork)
  • RIC Compaction of the earthwork
  • Installation of earth mat
  • Construction of HV equipment foundations and oil catchment dam
  • Construction of the new MV switchgear room and modification to the existing building
  • Access road construction with butemin surfacing construction
  • Erection of steel structure for HV equipment

Primary Plant:

  • Supply, install and commission 1 x 45MVA 88/11kV transformer
  • Reposition 2 x 45MVA 88/11kV transformers.
  • Supply, install and commission 88kV SF6 switchgear.
  • Supply, install and commission 88kV CT’s and VT’s.
  • Stringing of twin bull conductor for 88kV outdoor yard.
  • Supply, install and commission 88kV electrical operated disc connectors.
  • Installation of surge arrestors and insulators.
  • Supply, install and commission SBV4 x 19 panel feeder board with Vamp Arc protection.

Secondary Plant – Protection and Control:

  • Design, supply and commission Siprotech numerical relays, 3 x 54MVA 88/11kV transformer schemes.
  • 2x 88kV incomer, buszone and 19x11kV schemes.
  • FAT and SAT of protection systems.

Fire Protection:

  • Design, install and commission addressable fire detection system with pyro shield gas suppression system, in the new and in the existing building.
  • Installation of ventilation system automated with fire control system.

Fibre installation:

  • Install fibre optic cables between the new control room and the existing room where automation panel is located.
  • Terminate fibre cable.