Interference voltages and currents from AC and DC dynamic stray power traction systems are not assessed with the ACPT software. This is a question that has been asked multiple times by engineers over the years. The primary reason is interference pickup and leakage currents occur from the tracks to ground as the train moves station to station versus from low voltage power systems . Other factors such as train loads varying along the track and make it even more difficult to assess which is covered below. All AC mitigation programs calculate the inductive effects from AC Power Transmission Lines to Product Pipelines. This induction is basically a transformer consisting of two conductors which consist of the closest phase wire to ground in relationship to the coated pipeline i.e second conductor. Transmission power line loads directly impact the AC voltages on the pipeline called Steady State voltages. However, these voltages can change based on the AC Transmission line load.
To determine AC or DC interference requires taking field measurements of structure to electrolyte potentials and line current readings to determine where these pick-up and discharge leakage areas are located. These measurements are difficult to model because there are many factors such type of track construction i.e. wood or concrete ties, rail bonding, insulated track fasteners, water drainage in tunnels, maintenance, age of system, etc., bond cables, and rail to earth resistance that impact the readings. Most of these factors need to be identified physically and field tested. Once they are located, they are typically the source(s) for discharge or pick up leakage currents impacting pipelines.