Otis Singleton
Locating buried electrical cables is a necessary skill for anyone planning to undertake landscaping or building work. There are a variety of methods that can be used to find these cables, from professional cable locating companies to DIY tricks. The former uses a tone generator and receiver to trace the cable, while the latter includes the use of metal detectors, magnetometers, and radio cable and frequency locators. Another DIY method involves generating a frequency on the line using a small engine ignition and an AM radio to detect it. Additionally, it is possible to induce a strong signal by winding a narrow gauge wire around the spark plug cable of a four-stroke engine and attaching the other end to the cable you want to find. This method also uses an AM radio to detect the signal.
| Characteristics | Values |
|---|---|
| Cable Locating Companies | Can trace the cable without it being live |
| Metal Detectors | Can find wire down to 2-3 ft |
| Underground Cable Locators | NOYAFA D3IN0580-B can locate cables up to 2 ft deep and 1000 ft in length |
| Radio Cable and Frequency Locators | Used to identify fiber optic, electric lines, and phone lines |
| Magnetometers | Used in areas GPR cannot access, such as uneven surfaces, woods, or wires buried deep into the ground |
| Magnetic Locators | Not suitable for electrical wires |
| Utility Locators | Suitable for electrical wires |
| Transmitters | Transmit a signal through an exposed piece of pipe or cable to allow a location device to find a buried section |
| Induction Method | Uses an electromagnetic field to detect unknown lines by using a receiver |
| Direct Connection Method | Requires the cable to be connected physically |
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What You'll Learn
Using a metal detector
Metal detectors can be used to find buried electrical cables. They work by emitting a radio frequency (RF) signal that penetrates the earth and interacts with the electric currents running along the buried cable. This interaction produces a magnetic field around the cable that is detected by the receiver. The strength of the magnetic field decreases exponentially with increasing depth. The receiver measures the amplitude of the magnetic field and determines the distance to the cable based on the exponential decay rate of the magnetic field.
There are a few things to keep in mind when using a metal detector to find buried electrical cables. First, it is important to know what type of material you are looking for. Most underground wires are found inside copper and aluminium conduits, with a steel core. Transmission lines are also made of aluminium. Most metal detectors will find these materials with ease.
Another thing to consider is the depth of the cable. Handheld cable locators can be used to measure the distance to buried cables. They work by measuring the time required for a signal to travel along a wire to reach a detector. This time is impacted by the signal strength and the speed of light in the air. By knowing the length of the wire, the distance to the cable can be calculated. Vehicle-mounted cable locators use the same principle, but instead of a wire, the cable itself acts as the transmission medium.
When using a metal detector to locate underground wires, it is important to set the discrimination settings as low as possible. Adjust the sensitivity of the detector as high as possible while still maintaining stability. If the wires are carrying a lot of current, the sensitivity should be lowered until the machine stabilizes. Swing the detector loop back and forth over the area until the signal indicates a metal target.
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Employing a cable locator
Cable locators are also known as utility locators, and they have become increasingly important in recent years as more cables are being buried underground. They work by injecting an electrical signal onto the cable, which can then be traced by the operator above ground. The electromagnetic field generated by the current in the cable can be detected by the cable locator.
There are many manufacturers of cable locators, including 3M Telecom Systems, ideal Industries, Radiodetection Corp., Metrotech Corp., avo International, and Subsite. Prices can vary from $500 to over $10,000, depending on the features of the device. More expensive models can locate deeply buried utilities, while models ranging from $700 to $1000 should be sufficient for electrical contractors.
If you are only handling a small one-time project, it may not be feasible to purchase a cable locator, so renting one may be a better option. This gives you access to high-end models, but you may not have enough time to master the device fully. Alternatively, you can hire a cable-locating company to perform the service for you.
It is important to note that cable locators may not detect all buried utilities, especially if they are not carrying a live current or radiating radio signals. In these cases, an electrical current or signal will need to be applied directly to the utility to enable detection.
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Transmitting a signal
The receiver then detects this magnetic field and determines the distance and direction of the cable based on the strength and decay rate of the magnetic field. It is important to note that the strength of the magnetic field decreases as the depth of the cable increases. This method is known as active locating, as it involves applying an electrical current or signal directly to the buried utility.
There are different types of cable locators available, including handheld, vehicle-mounted, and pole-mounted variants. These locators may also have additional features, such as depth indicators, which provide information about the depth of the buried cable. The price of cable locators can range from $500 to over $10,000, depending on their capabilities and features.
It is worth mentioning that there are also passive locating methods that rely on detecting the cable's own current without inducing an external signal. However, active locating is often preferred as it can detect a wider range of utilities, including those that may not carry a live current or radiate radio signals.
Additionally, when transmitting a signal, it is important to consider the frequency being used. Higher frequencies can detect more signals but lower frequencies are better for following a specific line. Multi-frequency cable locators offer the advantage of being able to select the appropriate frequency for the specific application.
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Digging carefully
Start by assuming a straight line between the visible endpoints of the electrical cable. This is often the most likely path taken by the cable underground. Begin digging carefully along this assumed path, using a trowel or shovel with gentle force. It is important to dig with caution to avoid damaging the cable or any surrounding infrastructure.
If there is any visible tape or marking on the trench, such as "buried electric line below," follow that direction. The depth of your digging should also be guided by the expected depth of the cable. If the cable is not rated for direct burial, it should be enclosed in a conduit, which typically maintains a consistent depth.
In some cases, you may need to dig a trench with a pick to locate the cable, especially if it is not buried at the correct depth. If landscaping or other work is being planned, it is advisable to locate the cable beforehand to decide if it needs to be replaced or properly identified.
When digging, be mindful of any nearby fences or structures. In the past, markers for buried cables included short pieces of conduit screwed to fences or digging exactly where fence posts or foundations are located. These areas can provide clues about the presence of cables.
Additionally, if you encounter a wet weather pond or other obstacles along the path, exercise extreme caution and consider seeking professional help or using cable-locating equipment to avoid accidental damage or injury.
Remember, safety should always be the top priority when digging near electrical cables. If you are unsure or uncomfortable with any aspect of the process, it is best to consult a professional or cable-locating service to ensure a safe and effective outcome.
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Using a magnetometer
There are three main types of cable locators: handheld, vehicle-mounted, and pole-mounted. Handheld cable locators are portable devices that measure the distance to buried cables. Vehicle-mounted cable locators are installed on vehicles and use similar principles to handheld devices. Pole-mounted cable locators are fixed to poles and also use similar principles to handheld devices. Many cable locators will have a depth indicator to show the depth of the target.
When using a metal detector or cable locator, it is important to note that they work best when the conduit is made from metal. If the conduit is plastic, the signal will penetrate the pipe and detect the metallic wire inside the power line. Additionally, if there is no current running through the cable, a passive ground cable locator can be used to receive the signal put out by that cable. If a current is running through the cable, an active cable locator would be more suitable.
It is also possible to induce a signal onto a buried cable by winding a narrow gauge wire around the spark plug cable of a four-stroke engine, such as a lawnmower. The other end of the wire is then attached to the cable you want to find. By starting the lawnmower and sweeping a portable AM radio over the ground surface near the location of the cable, you can track the signal and find the cable. However, this method only works if the cable is not buried too deep.
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Frequently asked questions
You can use a cable locating company, which will use a tone generator and receiver to trace the cable. Alternatively, you can rent or buy a cable locator, such as the NOYAFA D3IN0580-B Underground Cable Wire Locator, which can detect electrical wires.
Yes, one method involves using a small engine ignition to generate a frequency on the line and an AM radio to detect it. Another method involves using a metal detector, but this may only work for cables buried a few inches deep.
Cable locators have two modules: a receiver and a transmitter. The transmitter sends out an electromagnetic field, which the receiver can detect. The cable gets the signal through either a direct connection or induction.
Before beginning any work, ensure that the breaker supplying electricity to the cable is turned off. It is also important to understand the route of the cable to avoid damaging it.
