The issues surrounding wind generation are not simple. While it's true that wind technology is cutting-edge, wind generation still faces significant hurdles. On the plus side, wind turbines are quick to market and reasonably priced, have no air emissions, do not need water and, most importantly, have zero fuel costs. On the minus side, the wind is not predictable and there are problems regulating voltage and frequency.

Wind farms have grown from small, experimental sites to facilities capable of generating hundreds of megawatts. As a result of technology advances and tax credits, wind-generated power has dropped in price from more than US$0.30 per kilowatt-hour 10 years ago, to a $0.04 to $0.06 range today. Worldwide, it is estimated that wind generation will exceed 35,000 MW of installed capacity by the end of 2003. U.S. installations are estimated to reach 6000 MW by year's end.

Quick to Market

Public Service Company of New Mexico (PNM; Albuquerque, New Mexico, U.S.) recently worked with a wind developer to connect a wind farm to the grid. In the process, the company realized a disconnect often exists between the utility and the wind developer. Wind-generation facilities typically progress from ordering equipment to commercial operation in three to six months. However, a utility's facilities, such as transmission lines and switching stations, can take years to permit, order and build.

An example of this is what took place when FPL Energy (Juno Beach, Florida, U.S.) approached PNM with the proposal to build the 204-MW New Mexico Wind Energy Center (the third-largest wind farm in the United States) in eastern New Mexico and connect it to the PNM transmission system.

Interconnecting a wind farm to a utility's transmission system poses several challenges. PNM had to tap and relocate a portion of an existing 362-kV transmission line on the PNM system. FPL Energy's wind farm has 136 GE 1.5-MW turbines, which extend for 15 miles (24 km) along the Taiban Mesa. Wind speed and turbulence vary over this large, exposing individual turbines to different wind conditions during the same period of time. This makes wind-farm power generation difficult to predict. It also adds to the inherent fluctuations in the output of the wind farm, which negatively affects the PNM system. This translates into issues of current harmonics, voltage flicker and voltage variation, which required PNM to launch a series of system studies to ensure the wind farm would perform in a safe and reliable manner once connected to the PNM grid.

Compressed Time Schedules

FPL Energy and PNM first began discussing the project with plenty of time to build the wind farm and the switching station. However, while the system studies and permits progressed, the interconnection and purchase power negotiations took longer than expected. Once the negotiations and studies were completed, the time remaining to build the facilities (a three-terminal switching station known as Taiban Mesa) had slipped to less than five months. Pulling this rabbit out of the hat would require some world-class magic. PNM had to have the Taiban Mesa station built and operating by the beginning of July 2003, but the project transition did not occur until Feb. 20, 2003.

The engineers at PNM had already standardized their approach to designing and building distribution substations, and they had access to an in-house design tool, 3D-DASL. The engineers had used 3D-DASL to develop a three-terminal ring bus station configuration capable of being expanded to a breaker-and-a-half configuration. A 3-D drawing set was produced, including a plot plan, cross sections and the beginnings of the foundation plan. The design for the 362-kV Taiban Mesa Switching Station was completed in a matter of hours, rather than the weeks normally required for this detail of design work, allowing engineers to concentrate on other issues.

Managed Business Relationship

PNM turned to GE Industrial Systems (Jackson, Mississippi, U.S.) to form a managed business relationship (MBR) for design, procurement, construction and project management. An MBR is an agreement between parties to share risks, hold each other accountable and trust each other to get the job done. PNM and GE had teamed up previously in this type of relationship to build two 362-kV series capacitor banks in record-breaking time.

With the MBR, GE and PNM formed a team to produce an interconnection point for FPL Energy. It was agreed that if PNM had a strong area, PNM would take the lead and make the decisions. Where GE had a strong area, GE took the lead. The companies studied PNM's standard station design. The team divided into subteams to work simultaneously on the protection and control schemes, the transmission line relocation, site development, communications packages, long lead equipment, detailed construction drawings and short-term equipment procurement. The teams coordinated many project design functions to allow for parallel design, specifying and procurement. With the extremely short time frame, the team could not afford time-outs for face-to-face project meetings. Personnel were scattered across North America (including Canada, Mississippi, Georgia, Colorado, New Hampshire, New York and New Mexico) with no central place convenient for all to meet. Therefore, conference calls in conjunction with Internet file sharing became critical in saving time and keeping everyone up-to-date as the work gained momentum.

Leveraging Existing Relationships

PNM established another MBR more than a year ago with GE-Hitachi HVB Inc. (HVB; Suwanee, Georgia, U.S.) for power circuit breakers. This MBR had been established to reduce paper work, save time and lower costs for power circuit breakers. At the start of the relationship, PNM supplied specifications, including voltage classes, for all power circuit breakers. HVB developed one set of detailed drawings for each voltage class of breaker. Both companies reviewed documents and created binding agreements for each voltage class.

In concept, PNM can call HVB and order a breaker and specify the delivery date. No one dreamed how thoroughly the Taiban Mesa project would test this concept. On Feb. 21, PNM placed an order with HVB for three 362-kV breakers to be delivered in April. A few weeks later, PNM asked for an additional breaker to be used in the FPL Energy's substation with a May delivery. All breakers were delivered on schedule.

Seeking a Construction Teammate

While procurement was happening, another part of the team began dialogue with construction contractors to find a company willing to accept the challenge of the Taiban Mesa project. After much negotiation, Great Southwestern Construction Inc. (GSW; Castle Rock, Colorado, U.S.) joined the team. Ground breaking for the Taiban Mesa Switching Station took place on March 3, 2003. March was spent with earthwork, grading and placement of foundations. By early April, the station was taking shape, and foundations were completed. Soon thereafter, steel emerged on those foundations, and station equipment began to appear in the lay down yard.

The First Milestone was a Killer

April was a huge milestone, both psychologically and physically. From the beginning, mid-April had been the deadline for the transmission line outage where the relocated station deadend structures would be put in place and the line relocated in the station.

Questions flew daily between the team and the manufacturers. Would steel be delivered on time? Would conductor be delivered on time? Dozens of items were needed to make the line relocation succeed. Some hardware did not make it in time, but another MBR PNM had developed previously with Priester Supply Co. (Arlington, Texas, U.S.) came through. Priester found much of the needed hardware in its multistate warehousing system and shipped it to the site. Some material was just unavailable because of the short time frame. PNM's line engineers, who recycled parts from older installations being removed from service, supplied those items.

Finally, all the material was in hand and the team was almost ready. The outage was scheduled for 10 days. Unfortunately, system constraints came into play again. The question was asked if the outage could be reduced to five days. Ten days was terribly aggressive given the amount of work defined; five days seemed impossible. GSW went off to study the relocation work. When it came back, it was with a “Yes, we can do it,” typical of the teamwork cooperation.

Time is Relative

May and June saw the station making steady progress, but dozens of problems still had to be overcome to meet the energization deadline. Equipment did not arrive at the station as promised. A call to the manufacturer revealed the equipment had not passed testing, so plan “B” was developed. The item was shipped to the station, and testing was completed on site. Hardware was missing, so plan “C” came into play. A metal fabricator made the part over a weekend. On one occasion, a supplier of a major piece of equipment told the project manager the factory had been closed and was being moved. All equipment would be at least two months late. That caused a scramble, but the team pulled off a minor miracle and found a replacement. The team took a “killing snakes” approach: Solve the problems one at a time. It did no good to become overwhelmed by the project. (It was a given; the project seemed impossible from the start.)

The Taiban Mesa switching station was energized on July 2, 2003. It was completed about 5:15 p.m. after a day of testing and commissioning. The Taiban Mesa station was built in four months and 10 days. The station consisted of three 362-kV power circuit breakers, nine 362-kV double-side break disconnect switches and nine 362-kV capacitive voltage transformers.

This project is an accomplishment that PNM is proud of, but one it would rather not have to repeat. Still, competitive pressures will keep PNM looking for even more innovative ways to deliver projects under seemingly impossible time restraints.

Gene Wolf, a contributing editor for T&D World, is principal engineer with Public Service Company of New Mexico, where he is responsible for the design and construction of EHV station facilities. He has a BSEE degree from Wichita State University and an MSEE degree from New Mexico State University. He is a senior member of IEEE and a registered professional engineer.
gwolf@pnm.com

Production Tax Credits

Wind generation of electricity is the leading renewable energy source in the power industry today. It was made that way by remarkable R&D programs and the support of U.S. and foreign taxpayers. In the United States, Congress passed the wind energy production tax credit (PTC) in 1992. It provided a 1.5-cent-per-kilowatt-hour credit (adjusted for inflation) for electricity produced by wind technology. This policy has expired twice in the past five years (1999 and 2001) and will expire again at the end of 2003. All indications suggest Congress will extend it, but it may not happen until after the end of the year.

In addition to the federal PTC, many states (including New Mexico) have approved their own state tax credits for wind developers and sponsored a renewables portfolio for the utilities doing business in their states. The New Mexico policy requires all utilities doing business within the state to have a 10% portion of renewable sources in the utility's generation mix by 2011 (as do other states, but the policy varies from state to state).

Wind: Yesterday, Today and Tomorrow

Take a public opinion poll asking what's the newest renewable energy technology, and most will say wind turbines. That would be the wrong answer. Actually, the first use of a large windmill to generate electricity took place in 1888 in Cleveland, Ohio, U.S. Charles F. Brush used a rotor 55 ft (17 m) in diameter to turn a dc generator, producing 12 kW. Another surprise is a windmill rated 1.25 MW in a 30 mph (13.4 m/s) wind operating in 1941. It was installed on a hilltop called “Grandpa's Knob” in Vermont. It only lasted a few hundred hours before metal fatigue caused the blades to fail, but it did work. Materials technology had not caught up with the mind's ability to conceive.

Today it is a different story. Advances in exotic materials, space-age aerodynamics, and microprocessor controls are enabling manufacturers to develop wind turbines capable of exceeding 5 MW of electricity generation. Tomorrow's blades will be lighter, more flexible and have independent pitch control. Improved materials will allow the pedestal to be taller, placing the rotor higher off the ground where the winds are more constant. These changes allow the turbines to be more efficient.

Power electronics also has improved. The latest designs are double-fed three-phase asynchronous induction generators with a pulse-width modulated IGBT frequency converter. Enhanced programmable logic controllers and computers have lead the way to variable speed controls, which lets the unit extract more energy from the wind. This technology also allows the turbine to absorb or produce reactive power, typically 0.9 lag to 0.9 lead as needed by the utility system. Other advances have provided turbines the ability to “ride-through” low voltage dips to 30% of the grid voltage for periods up to 100 m-sec (6 cycles) letting turbines remain on line through system disturbances.