Most probably you have seen the colored balls hanging on power lines and wondered what the purpose of the balls on the power lines is? Or why there are balls on the power line? We have decided to compile a guide to help you understand the significance of the balls on power lines.
Why are there balls on power lines? The round balls on power lines are known as aerial marker balls placed there to help save lives by acting as a visual warning to low flying aircraft.
The aircraft warning spheres on the transmission lines are instlled near small airports and where power lines run on a large open ground such as lakes, planes, and canyons.
The aerial markers power lines are big and colored so that aircraft pilots can be able to see them from a far.
Table Of Contents
Purpose of Aerial Marker Balls
Design of the aerial marker balls
Balls on power lines purpose are to prevent damage and loss of lives when low flying aircrafts hit and get entangled on the power lines. They warn pilots of the impending danger posed by the power lines.
The International Civil Aviation Organization (ICAO) recommends that the balls should not have a diameter less than 600mm. Each ball should be of single solid color, and the orange balls on power lines should be displayed alternately with white balls or red and white balls on power lines.
The colored balls on power lines should contrast with the background so that they can be easily seen. The round balls on power lines are made of 2 hemispheres which are clamped on the power line with aluminum alloy clamps. The clamps size depends on the earth wire dimensions.
They are made from the finest quality FRP and polished on both sides. The color is infused with ultraviolet-resistant pigment to extend its life. The materials used are to ensure the sphere has negligible weight.
Drain holes incorporated in the sphere prevents water accumulation in the sphere.
The aerial marker balls are easy to install as they come in two spheres which are bolted around the wire.
a)Spacing
The aerial balls markers should be spaced equally along the wire with a gap of 200 feet (61meters) or a fraction of this length. In critical areas, the distance between the balls should be less at 30feet to 50 feet (10 to 5meters).
They should be fitted on the highest wire or placed at the same height with the highest wire by other means. If there is more than one wire at the top, the aerial markers should be installed alternatively on each wire as long as the recommended distance is kept.
When the balls are fitted on more than one wire the weight and wind-loading factors will decrease on each wire.
b)Installation pattern
The round balls on power lines are installed in an alternating color scheme for optimum background contrast. The alternating colors help to capture attention to the power lines and prevent aircraft from hitting the wires.
c)Compensating for wire sag
Wires are bound to sag due to the increase in temperatures, the weight of the wire and wind. The maximum allowed distance between a wire that has balls installed and the one without is 25 feet (7.62m)
d)Multiple transmission lines
If there are multiple transmission lines on a certain location aerial markers are installed on an adjacent line if the distance between the outside lines is greater than 200 feet (61 m). If the distance is less than that there is no need for aerial markers balls on adjacent lines.
1.ABS Standard Marker
It is the most common type of marker Used since the 1960s. They feature a spiral line to fasten the ball on the power lines securely. They have superior color retention characteristics, and they are easy to install from the ground, bucket or helicopter. They are available in 6", 20", 24" and 36" sizes and their prices start at $170.
2.EHV 115kV+ Marker
These types of markers are specifically designed for installation on power lines of up to 345 kV. A special coating and extra design features are incorporated in these markers to reduce corona effects that can cause burning or melting which can occur in standard markers. The prices for these markers start at $695.
3.High-Temperature Marker
These balls are used in high kV, or high-temperature lines (ACSS/ACCR) rated up to 550 kV or 250oC (483oF). They made of aluminum which to minimize the weight where the 36" ball weighs 20 lbs. They are available in 12", 24", 30" and 36" sizes and cost starts at $295.
4.Modern Self Illuminated Marker/Light
They are designed with 2 LED lights illuminated 24/7 to make power lines more visible day and night. The FAA Advisory Circular 70/7460-1l of Dec 2015 calls for marking of all power lines with self-illuminated marker balls. They should be installed directly on the highest energized line from 15 kV to 500 kV carrying 40-2,000 Amps.
They contain a flux capacitor and a solid state regulator which pick up electrical field generated by the power line to light the 2 LED lights.
They are made of aluminum and are available in 12", 24" and 36" diameters.
5.Low-Cost Marker
These are less costly at prices starting at $199 for low budget projects. They are made from ABS, and they have rubber strips for mounting. They are made in small diameters of 9" and 20" but they meet the FAA advisory for small markers. These markers are used on small power lines which are below 50 feet.
We hope now you understand more about the aircraft warning spheres on power lines. Next time you are in the countryside and you happen to see these balls on the power lines you will understand their purpose, the color coding, and their spacing.
If this article has helped you or you have any questions about the aerial marker balls, feel free to leave a comment below, and we will get back to you.
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