The Effect of Transmission Lines on Railroads

This item is excerpted from an article at T&D World. Read the full article here:

In the electric industry, many workers are familiar with induced voltages and their potential impact on electrical work. Typically, crews are informed about other nearby power sources in the morning job brief, prior to the start of construction. Something not often discussed is that the same concept of voltage being present on supposedly dead conductors also affects railroad signaling, operation and safety.

In the modern era, railroads are moving to much more complicated signaling while still using the rails as the fundamental medium for communications. They have moved away from DC systems and now favor alternating-current (AC) frequencies to transfer their signals. This, in coordination with expansive relays and signaling devices, makes the signals much more susceptible to power line interference, which also is AC. Making the issue even more significant is the frequencies used often approach power line frequencies (60 Hz in the United States) and their harmonics, which makes it much easier for interference to occur.

Because of recent changes in railroad signaling technology, all railroads are becoming more and more susceptible to interference. If not appropriately mitigated, this interference could cause railroads to shut down and even damage their signaling equipment. In many cases, the interference also can make it difficult for the utility to obtain line outages. As the utility continues to use land next to railroads, induction studies should be completed more and more frequently to ensure the two systems can operate in harmony.”

BONUS: Here’s a video of a line being strung across an active railroad track:

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