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Project Scope

As part of the new Pannawonica substation, Partum was engaged to conduct an Earth Potential Rise (EPR) and Low Frequency Induction (LFI) hazard analysis for an existing high-pressure gas pipeline intersectig with a new 33kV overhead distribution powerline.

Challenges Overcome

Due to the high proximity of the high-pressure gas pipeline to the new 33kV overhead distribution line there were concerns with the electrical hazards that may appear on the pipleine during both normal operating and fault scenarios.

Solution

In order to ensure that the magnitude of the hazards was limited to safe levels, the HiFREQ module of the CDEGS software packages was utilised to build a model incorporating the following data:

  • Soil resistivity data from the specific location.
  • Maximum fault levels and fault clearing times for the 33kV distribution line.
  • 33kV distribution line profile and easement details.
  • Gas pipeline construction and route.

Various fault simulations along the distribution powerline were performed and the effects on the gas pipeline analysed. During the analysis it was determined, if gas pipeline appurtenances (i.e., valves and test points) are located within 110m of the studied distribution poles during an earth fault scenario, potentially hazardous voltages may be present on the gas pipeline appurtenances.

For appurtenances potentially located inside this radius, a recommendation to install a 50mm layer of asphalt around the assets was made. Due to the high resistivity of asphalt, the severity of the potential voltage hazards was reduced to magnitudes considerably below the allowable voltage limits.

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