NS260

NS260: Sub-Transmission Feeder Earthing

This document provides guidelines on the design and construction of sub-transmission feeder earthing systems. The key aims are:

• to manage the risk of electric shock from step and touch potentials;
• to prevent equipment damage;
• to ensure the earthing system components are sufficiently robust to perform their intended duty
  for the design life of the asset;
• to aid substation earthing compliance by maximising feeder fault return current; and
• to minimise outages due to transients

This Standard addresses electricity distribution network management guidelines and responsibilities specified in:

• NSW Dept of Trade & Investment - Code of Practice Electricity transmission and distribution asset management – February 2009;
• NSW Work Health and Safety Regulation 2011; and
• Ausgrid management plans

Scope

The scope of this standard is limited to documentation, design and construction of earthing systems for 33kV, 66kV and 132kV sub-transmission overhead and underground feeders.

This standard provides controls for the associated risks as listed below:

• The scope of this standard is limited to documentation, design and construction of earthing
  systems for 33kV, 66kV and 132kV sub-transmission overhead and underground feeders.
  This standard provides controls for the associated risks as listed below:
• Electric shock
• Damage to equipment
• System outages

Sub-transmission feeder earthing systems shall be designed in accordance with this Network
Standard. Requirements for the following are provided in this standard:

• The objectives of sub-transmission feeder earthing design,
• The design documentation required for each phase of a project,
• Items that must be considered in the design, and
• Standard constructions that should used

Further guidance on the earthing for the terminal equipment (e.g. GIS or cable stand) can be found in NS222 – Major Substation Earthing Layout Design.
Further guidance on lightning and insulation coordination can be found in NS 264 – Major Substation Lightning Protection and Insulation Coordination.