Frequently Asked Questions on Electrical Effects
Will television reception be affected by a transmission line?
Reception of cable TV, satellite TV, and digital TV signals are unaffected by radio noise from transmission facilities. If you think that you might be experiencing poor television reception as a result of a transmission line, please give us a call. Although we cannot do anything about poor reception you had before the transmission line was built, if interference does occur after the line is built, the problem often can be solved by changing or relocating the TV antenna.
Will radio, cellular phone, or wireless internet reception be affected by a transmission line?
AltaLink's facilities are designed and operated to minimize levels of radio interference and to meet Industry Canada?s interference regulations. AM and CB radio reception might be affected, particularly when directly under a transmission line. The type of radio, antenna, and distance from the radio station can affect whether interference is experienced. Higher frequency radio signals, such as FM, cellular phone, and wireless internet, operate above the general range of potentially affected frequencies and should not experience reception problems as a result of a transmission line. AltaLink will investigate if your service provider suggests a transmission line is affecting your service.
Will a Global Positioning System (GPS) receiver be affected by a transmission line?
Interference from transmission facilities on GPS equipment is unlikely. The signals sent to GPS receivers from satellites have frequencies far above the range of frequencies potentially affected by radio noise from transmission lines. Research has shown transmission lines do not cause errors or malfunctions for modern GPS equipment. Contact AltaLink if you believe your GPS receiver is being affected by AltaLink?s facilities.
Will my cardiac pacemaker be affected by a transmission line?
Experimental studies have reported that strong electric and magnetic fields have the potential to affect the function of a pacemaker if these fields exceed a pacemaker's immunity level. Pacemakers are designed to minimize the effect of interference whatever the source and so even though a change in function may be noted, it does not mean that a patient is at risk. Magnetic field levels directly under a transmission line are but a fraction of a pacemaker's immunity level to magnetic fields. Electric field levels under some transmission lines may be comparable to the pacemaker's electric field immunity level. While electric fields may affect some models of pacemakers, this would be most likely directly under higher voltage AC transmission lines operating at 500 kV since electric field levels drop rapidly with distance and are shielded by many materials. AltaLink is not aware of any cases of confirmed interference to pacemakers by transmission lines.
In addition, most modern pacemakers are designed to filter out electrical interference or revert to a safe mode of steady pacing (called asynchronous pacing) if interference becomes too great. Your doctor will be able to identify if interference has occurred by reviewing the telemetry data on your next visit. If you have a concern about potential interference from exposure to an electric field, contact your doctor.
How are nearby metal buildings and wire fences affected by a transmission line?
Electrical charges will not normally accumulate on buildings close to transmission lines because appropriate grounding already exists. AltaLink will help ensure that metal buildings, fences, including electric fences, and other structures close to our facilities are properly grounded to avoid the build-up of an electrical charge and possible nuisance shocks. Let us know if you are planning to put up a new building, fence, or gate near an existing transmission line, and we will advise you on how to ground the new structure and ensure it will not block access to the right-of-way.
Will the transmission lines or substations generate audible noise?
Sometimes noise can be heard from high-voltage transmission lines and is made up of a crackle and a lower frequency hum. The noise may be more noticeable in rainy or foggy conditions than in fair weather; however, noise from wind, rain, traffic, or industrial sources often masks the low levels of audible noise generated by the transmission line. Substation transformers produce a low-frequency hum that might be heard close to the substation; and transformer cooling fans create noise when they are operating. AltaLink designs and ensures their transmission lines and substations comply with the Alberta Utilities Commission Rule 012 for noise control.
Is there a difference between alternating current (AC) and direct current (DC) transmission lines?
Since AC and DC differ in frequency, the EMF produced also differs in frequency. For AC equipment,the polarity of the voltage and current change direction at 60 Hz, producing ELF EMF that changes direction at that frequency. For DC equipment, the polarity of the voltage and current remains constant at 0 Hz, producing static fields that also do not change direction. AC and DC fields act independently from each other. Only AC fields are capable of inducing currents and voltages in conductive objects such as fences, buildings, and humans. Corona effects such as audible noise and small amounts of radio interference occur near both AC and DC lines. While corona effects on AC lines are usually higher during wet conditions, corona effects on DC lines are generally higher during fair weather.
Will a transmission line be a source of stray voltage?
Stray voltage can cause behavioural problems in livestock if they perceive a voltage through contact across two points. This is different than a nuisance shock from an ungrounded metallic object that is in close proximity to a transmission line. AltaLink will mitigate nuisance shocks through our normal grounding practices.
Stray voltage problems are primarily related to distribution systems and on-farm wiring, both of which rely on the earth as a path for some of their current to flow. In these circuits, unbalanced loading on electrical panels, the use of distribution system neutrals and/or wiring problems can cause a current to flow into the earth (ground) at the load service point. Transmission lines might influence stray voltages only where long sections of on-farm wiring or distribution lines are built very near and parallel to the transmission lines, causing currents to be induced onto the neutrals of these facilities.
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