Induced Currents

When conducting objects such as vehicles or people are in an AC electric field, currents and voltages are induced in them. However, electromagnetic induction does not occur with DC because the current flow that causes the magnetic field is constant rather than alternating. The SOO Green project utilizes Direct Current (DC) technology that eliminates electromagnetic induction.

As additional background induced current with HVAC transmission varies with the electric field strength, the frequency of the field, the size and shape of the object, and the object- to-ground resistance. When a person or animal contacts a conducting object that is insulated from ground within an electric field, a perceptible current (tingling sensation) or a shock may occur. Another short-term effect of oscillating electric fields is direct perception of the field. The alternating charges induced by an electric field on the body surface can cause a detectable sensation through hair vibration. The amount of current is determined by the electric-field strength, the size of the object, and how well both the object and the person or animal are insulated from ground. The maximum body current induced in a person (across the ankles) by a maximum transmission-line electric field (10 kV/m) falls within the range of natural current levels[1].

Charge will also accumulate on insulated objects near DC lines. Typically, the DC current coupled by the flow of ions through air to people and objects is very much smaller than the currents induced by AC transmission lines. Utilities have mitigated problems associated with electric shocks from induced currents caused by transmission lines by following standards for grounding stationary objects such as fences, metal roofs, and antennas. Nuisance shocks near a +500-kV DC line are significantly less likely than for 500-kV AC lines. Due to the electric field isolation from the insulated and shielded cables and the absence of air ions in the underground installation, the SOO Green transmission line will further reduce the prevalence of induced currents and nuisance shocks.