When you look at the average utility pole on your street, determining what each component does can easily become overwhelming.
Although the arrangement seems complicated, many of the wires, cables, and components on the pole help power homes and businesses across the United States. The system is simple, yet elegant, forming the backbone of the final leg of our power journey.
But what do all those components on the power pole do, and how do they work together to keep the lights on?
If you go outside and look up at an electrical pole near your home, you’ll likely see several types of wires.
Note: Although some of the cables may not carry electricity for service, they still carry currents. If you see a downed wire, DON’T go near it and DEFINITELY DON’T attempt to move the wire under any circumstances. Instead, call your local utility to report the issue and let them handle it.
Primary wires are part of the primary power distribution system and sit on top of the power pole. Typically, they’re positioned along the top crossarm and atop the pole itself.
These wires carry power from local substations to neighborhoods and can reliably carry around 15kV. Unfortunately, the voltage in these cables is way too much for a home or small business. To ensure it’s safe for homes, transformers help step down the voltage to safer levels before reaching its final destination.
You can find these wires bunched together below the transformer (the metal canister-looking thing) on the power pole. They’re the last step in our power journey from the plant to our homes.
Often, there will be three cables, known as a triplex, running from the transformer to an access point on your home or business. Within the triplex are two insulated, or hot, wires and a bare neutral wire. Unlike primary wires, drop service wires only carry 120/240V, safely powering our laptops, TVs, lights, and other electronics.
For large residences, apartment buildings, and commercial businesses, a triplex cable might not have enough power. In this case, utilities may use a quadruplex wire, which is a three-phase version of a service drop wire. In this case, there are three insulated conductors and a bare neutral wire.
Note: When we refer to a three-phase system, it’s a system with three alternating currents. Each phase is 120 degrees apart to provide consistent and steady power.
Depending on the installation, these wires can either be copper or aluminum. Aluminum is cost-effective and lightweight, which is great for longer runs and overhead power service projects. Copper, on the other hand, is more conductive and easier for crews to work with, which is well-suited for projects where high conductivity is crucial.
In areas where electrical service is underground instead of on poles, utilities rely on USE-2. Utility companies bury USE-2 cables in trenches to protect them from weather, abrasion, and other threats.
To protect underground electrical wires and easily locate them later on, workers bury red tracer wire alongside them. The tracer wire doesn’t carry electricity to the home but creates signals to alert utility crews to underground lines.
Like other neutral wires, this one completes the electrical circuit from the pole to the home’s service entrance. In the case of a fault or short, the neutral wire provides a low-resistance path to safely move electricity back to the pole.
Ground wires provide a safe electrical path for electricity to get to earth. This copper wire runs vertically down the length of the pole.
Beyond serving as a nifty 1-2 punch alongside the neutral wire to handle errant electricity, ground wires protect systems. On power poles, ground wires direct electricity from lightning strikes to the ground, protecting sensitive components.
As we work our way down the utility pole, the communication wires are the ones closest to the ground. They carry everything we need to stay connected with each other, from telephone and cable TV lines to internet cables.
Surprisingly, although communication cables aren’t power lines, they do carry voltage! The voltage levels are low but can still injure people and pets if damaged.
Unlike other wires on the pole, guy wires are solely for stability. These structural tension wires attach to anchors installed in the ground to stabilize the pole.
In many cases, guy wires have brightly colored plastic protective wrap around them, called guy guards. Guy guards do exactly what you think–prevent damage to the guy and keep people from constantly tripping over them.
Now that we’ve covered all the wires, let’s explore the other components that help safely bring electricity to our homes.
Electricity from the power plant is a much higher voltage than we can safely use in our homes. Transformers adjust the voltage up or down during the electricity’s journey.
Transformers seen on our local utility poles look like canisters and step down power from the primary wire. As high-voltage electricity enters the transformer from the power line, it creates a magnetic field. That magnetic field, found around the primary winding, creates voltage in the secondary winding. Once the power leaves the secondary winding, it travels through secondary or service drop wires to homes.
Generally, the voltage coming out of a pole-mounted transformer is 240 or 120 volts, which is safe for home and business use.
Insulators sit on the utility pole’s crossbar and prevent primary wires from touching each other or the pole.
Without insulators, utility poles could become energized, putting people and animals at risk of electrocution. Additionally, if primary wires touch, faults and short circuits could cause power outages.
Depending on the application and location, they have several different variations, including pin, post, and suspension. You can also find several different materials on the market, including porcelain or polymers made from fiberglass and silicone.
These small devices protect transformers and other sensitive equipment on the pole from voltage surges. The arresters are idle most of the time but activate when power surges or lightning strikes occur.
If voltage levels rise above safe levels, the arrester immediately diverts the electricity to the ground. Once the electricity has passed through, the arrester idles, and the system can operate normally.
Sometimes called cut-out fuses, these mechanisms trigger when there’s a surge, overload, or other problem with the line or transformer.
When currents surpass the max rating, the cut-out’s fuse melts, breaking the circuit and limiting potential damage. The melted fuse then opens the circuit, drops from the fuse holder, and hangs from the assembly.
When crews survey damage, they can spot the open cut-out assemblies and quickly pinpoint issues.
Pole-top switches aren’t on every utility pole, but are more common in rural areas.
These switches allow electrical crews to quickly de-energize line sections for repairs or routine maintenance work.
The electricity we use to watch TV, make breakfast, and send emails travels a long way to reach us.
Luckily, the last part of its journey takes place just outside the front door. Depending on the situation, homes and businesses have one of several service drop cables coming to their homes.
Triplex wire has three wires–two “hots” and a bare neutral conductor. This provides reliable single-phase power to the average home.
For larger homes and businesses, quadruplex wire is more effective. In this case, three hot wires and a neutral conductor supply constant, steady three-phase power.
Another available option, especially in areas where electrical service is underground instead of on poles, is USE-2. Utility companies bury USE-2 cables in trenches to protect them from weather, abrasion, and other threats. To protect these wires and easily locate them later on, workers bury red tracer wire alongside them. The tracer wire doesn’t carry electricity to the home but creates signals to alert utility crews to underground lines.
To the average person, a utility pole might as well be a hieroglyph, but all those wires serve a vital purpose.
Electricity is an overwhelmingly important part of our lives, alongside TV, telecom, and telephone access. Without every component, we couldn’t get reliable, safe power delivered to our homes.
Utilities carefully maintain each piece to guarantee the lights stay on when needed most. When they aren’t on, those same components work together to keep us safe until electrical work takes place.
Next time you scope out a utility pole, take a breath knowing everything up there is reliable, consistent, and safe.