Effect of HVAC system on neighbouring pipelines and communication cables

Sharing of common corridors between power lines, pipelines and telecommunication lines is becoming a familiar scene. High levels of voltages can be induced in services which run in parallel or in close vicinity of high voltage AC transmission lines, in particular during a fault on the transmission line. These hazardous voltages can affect people coming into contact with exposed metallic objects under the influence of induced voltages. This may also harm components associated with the telecommunication or pipeline assets such as cathodic protection system. This paper investigates the effects of HVAC transmission lines on metallic objects that run parallel or in the vicinity of a power line such as gas pipelines and telecommunication lines. The study is performed on the 132 kV double circuit transmission line that has been recently installed to connect Pinjar to Wanneroo substations in Western Australia. The system under consideration was modelled and field measurements were obtained to help co-ordinate a safe working environment for personnel which may come into contact during a single phase to earth fault. Simulation and field measurements show that the Telstra infrastructure is not affected by low frequency induction (LFI) or earth potential rise (EPR). However, the LFI voltage level on some sections of the gas pipelines is found to be above the acceptable voltage limits set out by AS/NZ4853. This will require an extensive mitigation work to reduce pipeline induced voltages during an earth fault.