ELECTRICAL PROXIMITY EFFECT
“Electrical proximity effect is the tendency of current to flow in undesirable patterns due to the presence of magnetic field generated by nearby conductor. “
When varying magnetic field conductors due to unequal distribution of current are placed close together. Eddy current induces in nearby conductor. Consider two adjacent conductors carrying current in the same direction, the concentration of current increases at the farthest sides. Whereas, the concentration of current increases at the nearest sides, when adjacent conductors carries current in opposite direction. This changing concentration effect over by side of conductors is proximity effect.
Proximity effect doesn’t exist in case of direct current supply as their is no changing magnetic field.
As shown in the above image, the concentration of current at the farthest sides is more in case of same current direction whereas, its concentration is more at nearest sides when current flows in opposite direction.
Usually, skin effect and proximity effect in transmission lines conductor of having less than 125 mm cross sectional area are negligible.
Effect of electrical proximity effect
- The overall current carrying capacity of conductor reduces.
- The alternating current resistivity increases.
- Losses in power system increases due to induced eddy current.
- It reduces the Q factor in radio frequency tuned circuit, broadening the bandwidth.
Factors effecting electrical proximity effect
- Electrical proximity effect arises due to changing magnetic field that co relates with frequency, so it increases with the increase in frequency.
- Electrical proximity effect increases with the increase in cross sectional area of conductor.
- Same like skin effect, proximity effect is more in solid state conductor then stranded conductors.
- The effect is more prominent in ferromagnetic materials.
Limiting electrical proximity effect
By using ACSR (Aluminum Core Steel Reinforced) conductors, we can limit the proximity effect. It uses steel conductor in the center that increases the conductor strength. This reduces the surface area of conductor resulting in less influence of proximity effect on current carrying conductors.