Apple Creek Takes Cable Locating Seriously

Feb. 1, 2009
Kidron Electric uses new locate technology on AEP's underground circuit.

Kidron Electric Inc. (Kidron, Ohio) has been setting poles and meters almost as long as the company has been in business. But in Apple Creek, Ohio, 6 miles west of Kidron, the 70-year-old company was faced with the different challenge of locating an AEP Ohio secondary line on private property on the customer side of the meter.

AEP Ohio, a subsidiary of American Electric Power (Columbus, Ohio), owns and operates 46,344 miles of distribution lines and 9226 circuit miles of transmission in Ohio and the northern panhandle of West Virginia. The AEP subsidiary serves 1.5 million customers in 920 communities including Apple Creek, population 973.

The challenge for Apple Creek was avoiding AEP's service line. The line ran almost parallel to the span of poles that Kidron was preparing to install next to the new Fairlawn Mennonite Church construction site. The crew estimated that the service drop was buried 36 inches and spanned about 300 yards from the utility pole on Emerson Street to the new church building. The power line crossed the same area where several of the poles were marked for digging.

In most cases, before any excavation occurs, the first thing the Kidron crew does is call Ohio Utilities Protection Service, the state's one-call notification service. But, because the job was on private property, the crew decided to locate the only utility that had previously been installed, that being AEP Ohio's electric line.

Locator Advances

Up until two years ago, Kidron had used a variety of locators that typically were only able to perform one function at a time. For example, if the operator decided to insert a tracer tape inside a non-conductive conduit, and induce and pick up the signal on the tracer tape, he or she used one device. If the locator was attaching directly to the target phone or electric cable and inducing a signal, the crew would use a different locator.

At a contractors' meeting, Kidron saw a demonstration of a completely new type of locator. This multi-functional locator could pick up any common frequencies from any range of transmitters at the push of a button. RIDGID (Elyria, Ohio) has been manufacturing the SeekTech SR-20 for three years. RIDGID is typically known for its hand tools, many of which Kidron has used in the past. The main reason Kidron purchased this locator was because of the many features available at one time.

The SR-20 basically has three modes: passive, inductive and direct connect. It not only traces transmitted frequencies, but it also offers advanced passive modes that allow users to search for other metallic lines that might be present. It also has a unique mapping display and audible tones. The receiver provides left-right direction arrows and constant digital depth. As the operator gets closer to the target line, the numbers get higher in real time.

Sweep the Area

The second thing the Kidron crew does on every job is sweep the area with the locator in the passive trace mode. In this case, this was mainly near the utility pole to make sure there were no other utilities in the ground. The telephone and cable TV risers had been installed at the pole, but there were no signs of anything in the area, except for the service drop. AEP's service drop had been installed early to the church for the construction project.

Energized lines are not something to mess with if at all necessary, so the third step in this locating process was to decide which method to use to locate the buried cable, the conductive or the inductive procedure.

The inductive or direct-connect procedure includes de-energizing the conductor. Crews disconnect the conductor from the load side of the breaker to ensure safety. The lead from the transmitter box is then attached directly to the bare wire of the utility being located. The other lead from the transmitter is attached to a ground stake, planted perpendicular to the target line. When the current is transmitted through the lead wire, the locator recognizes this unique signal and interprets the necessary data via digital gauges and graphics on the locator.

Kidron mainly uses the conductive or direct-connect mode when other utilities are nearby to minimize bleed-off and signal distortion. In very dry soil conditions, which make the soil non-conductive, crews sometimes pour water around the grounding rod to increase conductivity. On the Apple Creek job, Kidron selected the inductive clamp mode, because it is less intrusive and easy to connect.

Inductive-Mode Setup

The inductive-mode setup is simple. On the Apple Creek job, one 12-kV phase-to-phase service line came down the pole encased in a 4-inch conduit. The operator plugged the clamp into the transmitter and then attached the 4-inch induction clamp around the conduit. The transmitter automatically shifted to induction mode when the clamp was plugged in. No ground stake is required when using the induction clamp. A unique signal was then produced by the transmitter and induced through the lead clamp on to the target conductor. The locate receiver is programmed to recognize this unique signal.

The operator then selected the appropriate frequency setting on the transmitter. A common rule of thumb is to use the lowest frequency and the lowest output possible. This helps to minimize bleed off and distortion caused by false signal bouncing off other metallic objects such as fence posts and other utilities in the ground. In this case, there were no known obstructions in the area, so the operator set a 32-Hz frequency and a medium output level.

One of the unique features that Kidron appreciates about the new locator is having all of the information displayed on one screen. Directional arrows and a "proximity number" increase closer to the target and help point the operator to the target line.

Marking the Line

To begin locating the buried cable, the operator traces the path of the target line sweeping the receiver from side to side. As he walks along in real time the locate device displays a map with a line in the middle. When the line and arrows line up, the operator knows he is running parallel to the target line. The crew marks the line of the buried power line with red paint, so the pole crew will know where the existing line is located.

Most utilities are installed with a trencher, so the depth rarely varies. In this case, the depth remained constant but the power line took a slight turn as it approached the church. The receiver was able to immediately detect this change as the directional arrows on the receiver changed telling the operator that the buried utility had changed course.

There was no reason to switch to passive mode, but if the operator suspected something else was in the ground as he was locating, he could switch to the passive mode and sweep the area. Previously, it would have taken Kidron about 30 minutes to locate an area this size. Despite the fact that the distance was more than 300 yards from the riser to the church, the locator was able to mark the line in less than 15 minutes.

Kidron work sometimes requires locating buried utilities inside industrial sites. The presence of other utilities is an additional challenge. Utilities are usually crowed together in a common utility corridor. For these projects, the crew tries the direct-connect conductive mode first. The signal is less likely to bleed-off onto other utilities, so a stronger signal can be induced resulting in a more reliable reading. The crew always has the option of switching to the passive-trace mode to help verify that the crew has located all of the utilities in the area.

Minimizing Danger

Kidron takes the job of locating very seriously. Any time ground is broken, whether to trench new cable or to install a pole, there is the risk of damaging other utilities. On the Apple Creek job, the challenge was to avoid hitting the power cable. Power is not only dangerous, but it also could potentially be fatal. Electrocution is the fourth-largest cause of construction worker death is the United States.

For all of these reasons, Kidron uses the latest locating technology available not only to minimize the damage to buried utilities but to minimize the risks to its workers, especially when working around power lines.

Vern Hochstetler ([email protected]) is electrical superintendent for Kidron Electric Inc., where he has worked for 39 years, 29 of which he spent in the field. His current duties include supervision of large jobs, overseeing crews, ordering materials and final inspection of all jobs.

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