Utility engineers have been faced with the challenge of finding ways to get more out of their lines and existing facilities without spending large sums of money. With few new transmission lines being built over the last 10 years, most work has been related to re-rating transmission lines, and adding telecommunication antennas to transmission towers and long-haul fiber to transmission lines. Although these activities have increased the revenue for utilities, they also have required more planning, coordination and attention when it is necessary to do maintenance or schedule an outage on an existing transmission line.

In the fall of 2003, TXU Electric Delivery (Fort Worth, Texas, U.S.) needed to relocate a critical line that also housed telecommunications facilities. With careful planning, up-front coordination and some weather cooperation, TXU relocated the line in record time without any loss of electrical or telecommunications services.

TXU needed to relocate five double-circuit 345-kV towers on its Royse Switching Station — NW Carrollton Switching Station line near Plano, Texas. Four towers in one stretch of the line had to be moved 10 ft (3 m) laterally in the right-of-way to accommodate the addition of a new double-circuit 138-kV line. The fifth tower had to be relocated 80 ft (24 m) in-line to accommodate the addition of the Austin Ranch Substation.

This double-circuit 345-kV line is a critical segment of a heavily loaded grid in the Dallas MetroPlex area. The utility could not schedule an outage on this line until mid-October when the temperatures fell and the loads decreased.

This situation is not uncommon. Nearly every utility in the country has embarked on a plan to re-rate and/or maximize the use of its extra-high-voltage (EHV) transmission facilities to avoid building new lines. Although this is a good and necessary approach, it increases the importance of each individual line to such a level that it is nearly impossible to get the line out of service in the future. When an outage is necessary, utilities must take major steps to limit the outage period.

TXU joined forces with consultant POWER Engineers (Hailey, Idaho, U.S.) for this relocation. POWER determined the best way to limit the 345-kV outage was to relocate the towers up or down the line 55 ft (19 m) and then move them laterally 10 ft. This approach would allow the installation of new stub angle, drilled-pier foundations outside the footprint of the existing towers. With low-headroom drilling equipment, the foundations could be installed without taking either an electrical or telecommunications outage.

Early field reviews and meetings made it clear this relocation was not going to be a simple task. In addition to two city street crossings and an apartment complex with parking under the EHV line, a third-party-owned fiber-optic cable (OPGW) was in the shield wire position on one of the circuits, a Burlington Northern-Santa Fe railroad crossing ran between Towers 33/2 and 33/1, and there was a third-party-owned telecommunications antenna and an OPGW splice on Tower 32/4.

POWER consulted TXU's Transmission Grid Planning Department as well as the telecommunications provider. The construction bid package was prepared with the assumption that a two-week continuous outage would be granted on the 345-kV line and a maximum 4-hour weekend outage would be allowed on the OPGW.

The OPGW, however, proved challenging. The cable was owned by a Texas-based communications company whose high-profile customers and high-traffic volume required the OPGW to remain in service at all times.

In addition, Tower 32/4 had an existing OPGW splice. The OPGW coil bracket had only two or three wraps (approximately an extra 25 ft [7.6 m]) on the bracket prior to entering the splice canister. The excess cable on the coil bracket was not long enough to allow the relocation of the structure to its new position without splicing in a new span of OPGW cable and adding an additional OPGW splice on Tower 32/3. Because of the fiber in-service requirements, the work would have to be scheduled on a Sunday with a “hot-splice” to cutover the traffic. The hot-splicing technique splices one fiber at a time, so end users never experience any data-transfer problems.

This situation is not unusual. Many electric utilities have obliged telecom companies over the last 10 years by adding fiber-optic cables to EHV transmission facilities. In the race to see who could get the most fiber (bandwidth) in place, telecom companies often considered EHV lines because they offered a direct path between populated areas. With little investment, telecom companies could add fiber-optic cables to EHV systems. While providing long-haul bandwidth solutions to the telecom providers, these fiber cables also provide a revenue source for utilities. However, as this example shows, the addition of these important, high bandwidth cables to EHV facilities — combined with America's desire for uninterruptible and reliable Internet service — have made it difficult to schedule maintenance work on these electric transmission lines.

In addition to the OPGW splice, Tower 32/4 contained telecommunications antennas. The telecommunications provider indicated this site could not be taken out of service without adversely affecting mobile telephone customers.

Telecommunications antennas are becoming more commonplace on transmission structures. Electric utilities with significant overhead line facilities frequently have been asked to add antennas, and many have obliged. All parties typically win when antennas are added to electric transmission facilities. The public is happy to receive better coverage, the telecom company is happy not to have to pay for a new antenna tower, and the utility is happy to have generated an additional revenue source.

However, as this example shows, the addition of these antennas to electric transmission structures creates a headache when future line maintenance or relocation is required. POWER handled this situation by planning to have a temporary mobile antenna, known as a cell on wheels (COW), installed and placed in service a couple of days before the tower relocation.

POWER's design also considered the location of the existing telecommunications cabinets and equipment. By moving the tower 55 ft (17 m) west and 10 ft (3 m) south, it could be lifted over the equipment, eliminating the need to relocate the telecommunications cabinets and their associated telephone and power infrastructures. This simple approach not only saved the telecommunications provider money, but more importantly, it minimized the time required to complete the relocation.

Reducing the relocation time proved imperative as the electrical outage window began to shrink from what had been anticipated. Not long after construction began in September, the electrical outage window that would be available became clear. A 10-day continuous outage was not possible. The best scenario was a continuous outage starting on Saturday, October 11, and extending through Thursday, October 16, weather permitting. Combining this schedule with the requirements of the weekend fiber outage meant the weekend of October 11 would be a serious test of the team's ability.

TXU awarded the construction contract to Red Simpson Inc. (RSI; Alexandria, Louisiana, U.S.) in early August 2003 and began construction in mid-September 2003.

On October 8, RSI began to mobilize three construction crews with 22 workers, as well as extensive equipment required to perform the critical outage work. The plan involved one 150-ton crawler crane to pick up and move the towers, four 60-ton RT cranes to support the conductors while the towers were being moved, and four truck cranes to serve as working platforms and guard structures. RSI also mobilized OPGW stringing equipment.

The COW was set up on Friday, October 10, and would remain in place until Tower 33/4 had been moved. RSI carefully placed all line equipment in preparation for the weekend work and went home early Friday afternoon hoping for a good night's sleep and good weekend weather.

On Saturday, October 11, the crews arrived early anticipating an early clearance on the two 345-kV circuits. The clearance wasn't granted until 10 a.m., and work began immediately at Tower 32/3. The later-than-anticipated clearance changed the day's plans but did not stop progress. By the end of the day, Tower 32/3 was moved to its new location, and the crawler crane was set up to move Tower 32/4.

Sunday, October 12, was the key day of the outage sequence. Crews relocated Tower 32/4 during the first half of the day and Tower 32/5 in the second half of the day. By early evening, the span of new OPGW had been pulled in, sagged and dead-ended. The crews pulled in the new OPGW alongside the existing OPGW to accommodate the no-fiber-outage requirement. RSI turned over the OPGW cable ends to the fiber cable provider for hot splicing. The splicers worked through the night and completely restored the fiber cable by 6 a.m. on Monday morning. The weekend had been a great success, and the rest of the work would be relatively simple compared to the first two days.

Tower 33/1 and Tower 33/2 were relocated on Monday and Tuesday. Production was limited to one tower per day, because the crawler crane had to be dismantled and hauled from one side of the BSNF railroad to the other.

The planning and coordination paid off: All five towers were relocated in a four-day period, beating the electrical outage window by two days.

Lessons Learned

With this project successfully under their belts, TXU and POWER are able to pass on the following lessons learned:

• Successful projects don't happen on accident — lots of planning is required. This is even more important on projects involving third-party telecommunications providers.

• Outage windows move and often shrink. Prepare a plan that can be executed in half the anticipated time and a couple of weeks in advance. Have plenty of equipment and more-than-enough manpower.

• Plan for inclement weather. Although this project benefited from excellent weather, this often is not the case.

• Get your contractor on board early so he can get involved with the design to limit construction durations. The POWER, RSI and TXU teams met several times during August to formulate a plan for the successful relocation of the five towers, the OPGW and the antenna. The team also met with the two telecommunications providers to ensure everyone was prepared when the outage window opened.

• Require OPGW installers to coil at least 100 ft (30 m) of excess cable on each splice tower. Had this been the case for the subject project, no new OPGW would have been required and thus no fiber splicing required.

• Make sure contract language with third-party providers is clear as it relates to future maintenance and relocation of both parties' facilities.

Rick Benson has been with TXU Electric Delivery for 22 years and is a project engineering manager in transmission engineering. His current responsibilities include managing the design and construction of overhead and underground transmission lines for the 69-kV, 138-kV and 345-kV system. Benson holds a BS degree civil engineering from Texas Tech University and an MS degree in engineering management from Southern Methodist University. He is a registered professional engineer in Texas.
rick.benson@txued.com

Randy Grass is a senior project engineer for POWER Engineers. As transmission line business director, he manages POWER's Transmission Line Production Departments in POWER's Hailey, Boise, Denver, St. Louis, Atlanta and Fort Worth offices. His expertise is in managing and engineering complex transmission line and telecommunications projects with fast-track schedules. Grass has a BSCE degree from the University of Missouri-Columbia and is a registered professional engineer.
rgrass@powereng.com