VRIOGS 010.4 RevA - Public Transport Victoria

VRIOGS 010.4 Revision A 19SECTION 13.0THE EARTH GRIDThe earth grid shall be laid in accordance with the design requirements.13.1 INSTALLATIONa) Before any preparation or form work is made for the reinforced concrete slab,the contractor shall install an Earth Grid System at a nominal depth specifiedon the design at a level below the finished floor level of the substation.b) Trenches will be cut in the sub soil to the required depth relative to thesurveyor’s marks approximately 200mm wide.13.2 INSTALLATION OF EARTHING ELECTRODESCopper earthing Electrode each 3 metres in length with a minimum diameter of16mm, shall be driven into the trenches at the design indicated points to a depth soas to leave approximately 100mm clear for cadwelding or brazing to the grid wire.13.3 BUILDING CONNECTIONS TO THE EARTH GRIDa) The switchroom main earth bar shall be connected the outside earth grid asper the design. Disconnection point for testing shall be at the main earth bar.There shall be some means to visually and electrically confirm the connectionof the switchroom earth bar to the external earth grid.b) Provision shall be made in accordance with design documentation forconnection of fences, slab reinforcement, transformers and all other metalcladequipment to the earth grid.13.4 TESTING OF THE WHOLE INSTALLATIONThe resistance of the earthing grid shall be tested in an approved manner afterinstallation together with the resistivity of the soil. This shall be carried out before theconcrete base is laid and the Department or its representative advised of the resultswithin 24 hours of the test being completed.Further construction work shall not proceed until the Department evaluates the earthgrid test results and confirms that the results are satisfactory.NOTE: This document is controlled only when viewed on the DOT Engineering Standards website.Any other copy of this document is uncontrolled, and the content may not be current.