| The path was cleared for a new electricity | | | | embedding fiber optic cable in these wires has made |
| transmission line in New York that that could not be | | | | these mechanical modifications quite a bit more |
| energized until interference problems with a | | | | complicated. |
| Rensselaer, N.Y., AM radio station were resolved to | | | | To evaluate and resolve the New York problem, an |
| the satisfaction of the New York Public Utility | | | | engineering firm was called in by CH2M Hill, an |
| Commission. | | | | international consulting engineering firm based in |
| After extensive onsite and computer analysis, | | | | Colorado. The eight disruptive transmission structures |
| engineers determined that 8 of 33 tall power towers | | | | were subsequently identified through field |
| on this line in the proximate area of station | | | | measurements and software modeling. Their negative |
| WGDJ-AM would disrupt the stations licensed | | | | impacts were remediated by an AM protection |
| coverage pattern and require installation of detuning | | | | detuning process, allowing the project to proceed. |
| systems. | | | | The offending structures were detuned using |
| The transmission towers carry a 345 kV electrical | | | | custom-engineered hardware along with modifications |
| power line from a 635-megawatt natural gas fired | | | | to the new power line. Modifications were carefully |
| power plant constructed in Rensselaer by Empire | | | | designed for safety and usability in conjunction with |
| Generation Co. LLC. The distribution system has 70 | | | | CH2M Hill and the owners, and implemented by LG |
| towers in all, the last of which were erected last | | | | Constructors. Necessarily, all detuning hardware was |
| summer. The question was how many of them near | | | | constructed, installed, and documented to rigorous |
| East Greenbush, N.Y., would cause signal interference | | | | utility standards. |
| with broadcasts of the AM station. The interference | | | | The process has been employed hundreds of times |
| would have created a violation of FCC rules | | | | to detune cellular industry towers with AM radio |
| governing the integrity of broadcast signals. | | | | interference problems of their own. While |
| Transmission towers often are a height that makes | | | | technological applications vary in each case, they are |
| for efficient radiation of medium wave AM signals. | | | | rooted in the same family of engineered solutions. |
| The broadcast AM signal is intercepted from the | | | | This was an important design consideration, as |
| environment by the power tower and "reradiated". | | | | renting transmission tower space to wireless carriers |
| This reradiated AM signal interferes with the designed | | | | is an important revenue source for utilities. In the |
| coverage and interference of the AM broadcast | | | | event the detuned towers were to be rented to a |
| antenna system. The Federal Communications | | | | carrier to support their antennas, the AM dutuning |
| Commission licenses AM station antenna systems to | | | | documentation would also support the carrier's FCC |
| very tight tolerances, and only a few percent | | | | AM protection requirements. |
| reradiated powerline signal can seriously impact the | | | | Interactions between high voltage transmission |
| licensed pattern performance. | | | | systems and AM stations are expected to grow in |
| The proper evaluation and remediation of power line | | | | future years. Thousands of miles of powerlines are |
| reradiation can be complex. The multiple transmission | | | | planned to support the smart grid, wind turbine, and |
| towers and the coupling between them through | | | | photovoltaic power generation. Many of these will |
| lightning shield wires can be a challenging analysis, but | | | | pass near AM broadcast antennas. It is vitally |
| also spread the impact much more broadly than | | | | important for utility planners to have proposed routes |
| would a single tower. These interconnections form | | | | reviewed by an RF engineer early in that process. If |
| conductive loops which have vastly different electrical | | | | lines can't be rerouted, then detuning can be |
| properties than single towers. Normally, a technique | | | | incorporated in the design process, at great savings |
| called "detuning" is applied, along with modifications of | | | | over construction stage delays or modifications. |
| lightning shield wires. The recent practice of | | | | |