On the 16 August 2018 Western Power published an updated FAQ on Earthing Standards. The updated FAQ includes changes to substation earthing layouts. These changes have been required due to increases in copper theft.
Changes to be aware of in the FAQ include:
- The grading ring is now 70mm2 bare copper coated steel conductor buried at a depth of 150mm below the finished ground line.
- The grading ring will no longer be connected to the high voltage (HV) earth electrodes.
- Separate connections to the HV earth electrodes require 70mm2 PVC insulated copper conductor buried at a depth of 1200mm.
- The earthing connection single line diagrams for the different substation configurations are shown at the end of the document.
- For the Modular Packaged Substation (MPS) only, 2 additional electrodes are connected to the grading ring. These grading ring electrodes are to equalize touch potentials. They consist of a single 1.5m long earth stake and do not have a target earth resistance.
Western Power will continue to specify prescribed values of earthing resistances in the short term but will be moving to risk-based earthing in accordance with AS/NZS 7000:2016 and AS 2067:2016 in the near future.