High capacity for long distances? Constricted rights-of-way? Aesthetically sensitive areas? BOLD is the key to solving them all.
BOLD® is a compact transmission line design that combines the advantages of higher capacity, lower energy losses, and a lower-profile structure with less visual impact. BOLD® was created to maximize the use of land for transmission line corridors (right-of-way) and avoid complex specialized equipment like series capacitors.
The benefits that BOLD® provides can help utilities achieve the objectives of new resource integration and infrastructure renewal with the highest efficiency and least environmental and community impact. The patented design provides an efficient and robust transmission solution at common domestic and international voltage classes representing the best available technology in overhead line design.
Not necessarily. Compact lines designs have been studied since the 1970s, but built in very rare circumstances at voltages 230-kV and below where right-of-way or some other constraint existed.
An EPRI survey performed in October 2014 found only six responding utilities that had compact lines on their system. However, the survey did indicate a growing need for compact designs.
Most utilities do not have a standard for compact transmission lines or sufficient experience to overcome the hesitation of adopting a new design. Historically, as the current grid was expanding, it was relatively easy for a utility to obtain the necessary rights to build transmission lines.
However, in today’s age, utilities are faced with significant challenges even when rebuilding lines in existing corridors. Compact transmission lines like BOLD® can be a useful solution that balances system needs with public and environmental concerns.
BOLD® is unique in that it was designed for capacity and performance first, but comes along with the aesthetic and environmental advantages sought by others who have pursued compact line designs. The synergy BOLD® provides makes it a solution that can be applied in a variety of ways.
Additionally, the extensive testing, vendor collaboration, and experience gained on real world BOLD® projects provide a new level of insight into the design and application of compact transmission lines.
BOLD® is currently designed and tested for 138-kV, 161-kV, 230-kV and 345-kV applications. Designs for both higher and lower voltage levels are contemplated based on market demands.
The BOLD® design can be built as a single- or double-circuit tower. The single-circuit version is simply half of the crossarm, though several tower variations are possible.
- Up to-60% increase in Surge Impedance Loading (SIL) per circuit
- Eliminate need for series compensation in long-distance bulk-power transfer applications
- Increases thermal capacity
- Increases power delivery in the same right-of-way
- Reduces energy losses from conductor heating
- Moderates electromagnetic field strength
- Provides aesthetic appeal that is preferred and more acceptable to general public
- Reduces structure height
- Reduces avian interaction
Lower surge impedance (higher surge impedance loading, or SIL) is achieved by compacting the phases while simultaneously increasing the conductor bundle diameter and number of sub-conductors. For example, 60% more SIL increment is obtained through a 40% surge-impedance reduction, which is directly related to reactance reduction through the compact delta design between three phases.
BOLD® design acts like a series compensated line but without extra equipment to maintain. Additionally, increasing the number of sub-conductors naturally increases the overall thermal capability (ampacity) of the line. The compaction of the phases is also what allows BOLD® to be constructed on shorter, streamlined structures.
While each project is different, most new transmission facilities are not much different than those built decades ago. Significant benefits can be achieved by increasing line efficiency, reducing line impedance, lowering energy losses and maximizing the use of new and existing rights-of-way.
Building transmission today also demands an earnest appreciation for environmental and public impacts. BOLD® was developed with these considerations in mind, providing a new and innovative solution for utilities to consider when planning the grid of the future.
Additionally, the industry stands to benefit from utilizing a tested, proven compact line design.
Extensive electrical and mechanical testing has been performed to ensure the design works in the field as it was designed.
EPRI Lab — Lenox, Massachusetts
- Single-phase corona cage testing
- Three-phase power frequency testing (wet and dry corona & audible noise)
- Lightning performance
- Switching performance
Hubbell Power Systems — Wadsworth, Ohio
- Single-phase insulator and hardware-assembly power-frequency testing
Burndy — Manchester, New Hampshire; Kinetics — Toronto, Ontario
- Spacer-damper mechanical testing
Valmont – Valley, Nebraska
- Full-scale structure testing
Because BOLD® has both performance and aesthetic advantages, the potential applications vary widely. The performance aspects of BOLD® make it a very attractive option for delivering large amounts of power over long distances — a challenge common for wind development.
In populated centers or areas with constricted right-of-way, BOLD® is a great option for increasing the voltage and/or capacity of a line without installing bigger structures.
Compared with typical lines, the impedance (R and X) is lower while the shunt charging (B) is higher. Exact parameters can be shared under a non-disclosure agreement (NDA).
It is important that transmission owners, planners and regulators understand what BOLD® is and why it is different. BOLD® lines can be modeled in planning analyses the same as conventional lines (with the modified parameters), and considered as a solution either as a new build or rebuild of existing lines.
The performance aspects of BOLD® are particularly evident in PV studies, demonstrating that more power can be transferred while maintaining stable voltages. The benefits of a high capacity and low impedance of BOLD® lines can also be seen in economic/market-efficiency analyses.
Of course, as lines are planned, the less tangible aspects of siting ease, constructability, and public impact should also be considered.
Wind resources are generally located far away from the areas demanding power, thus requiring long transmission lines for transport. Historically, series compensation has been utilized to increase transfer capability on these lines for performance needs.
Series capacitors can create harmonic interference known as Sub-Synchronous Resonance (SSR), which can interfere with and even damage turbine generation facilities. Series capacitors are also complex and costly.
BOLD®’s compact line design, not requiring series compensation, is able to perform equal to or better than a traditional line with series compensation and avoid this potential complication.
The following vendors were involved in developing the first application of BOLD®:
- Steel pole structures — Valmont Inc.
- Insulator hardware assemblies — Hubbell Power System, Inc.
- Construction — PAR Electrical Contractors, Inc.
- Other competent and reputable vendors and contractors should be able to design BOLD® components and construct/maintain the line. A training program is available to those who will design, build, or own/operate BOLD® lines.
Knowing each project is unique, the BOLD® design can be customized depending on the application. The first BOLD® line operates at 345-kV with a 3-ACSR Cardinal conductor bundle on tubular steel poles and a smoothly curved crossarm.
The 230-kV version is essentially a scaled version of the same tower. 2-, 3-, and 4-bundle conductor arrangements can be utilized dependent on project needs/requirements. A BOLD® lattice family of structures has also been developed and was implemented in BOLD®’s second application (which was energized in July, 2017).
By keeping the same phase configurations (phase spacing, bundle size and diameter, conductor size), other conductor types can be used for different purposes for BOLD® line design. Sag-tension of ACSS, ACCC, or ACCR conductor types can be designed and matched to ACSR to maintain the same overall structure height.
Yes. While the first BOLD® projects utilize polymer insulators, other materials may be used.
In most cases no, but this will be a function of each project’s unique geography. The height reduction is a benefit due to the compaction between phases. The bottom phase conductor attachment height and phase-to-ground clearance is the same as the lowest phase on a traditional design.
The BOLD® design includes maintenance vangs and working holes on the structure, working holes on the yoke plates, and select hardware connections that are appropriate for foreseen maintenance activities. A climbing hot box was also provided. Since work practices vary widely between utilities, it is up to the licensee to determine whether or not they can perform live line maintenance.
BOLD® has developed methods and techniques for maintenance on BOLD structures.
Traditional structures can also be temporarily utilized on up to 5% of the total line length without altering system performance. As BOLD® is adopted as an industry-wide design, sparing capacity will increase.
BOLD® uses a compact delta phase super bundle (C1-C2-C3/C1-C2-C3, top-to-bottom) arrangement. Up to a 50% reduction in magnetic field at ground level is achieved using this arrangement for the same power flow.
BOLD® can be built in narrower rights-of-way, making it an excellent choice for rebuilding existing corridors. Right-of-way width is a function of span length (i.e., number of structures) and environmental considerations (e.g., audible noise, EMF).
Audible noise for BOLD® is comparable or lower than a traditional design, and magnetic field strength is lower so regulations can be met with a narrower width. BOLD® can also be designed with the two circuits over top of one another to fit a double-circuit tower in a right-of-way as narrow as 50 feet while still meeting regulations.
There are two shield wires attachment locations on the top of the curved beams. These two shield wires are to provide zero degree shielding angle to the outermost phases. Shield wires can be either OPGW or regular static wire.
Testing demonstrated that lightning performance is as good as or better than traditional designs.
AEP is using BOLD® for projects today. See the Projects tab for more information.
The BOLD® technology is available through licensing, partnerships, or other arrangements. Contact us for more detailed information.
Yes. BOLD® currently holds 14 issued and pending patents worldwide and can work with utilities outside the U.S.
A late 2015 survey polling the general public across the United States and throughout Europe found strong favorability of BOLD® vs. traditional designs in all areas.
The public valued the reduced height and aesthetic appeal of BOLD® and strongly favored their local utility in implementing new technologies such as BOLD® in future projects.