New technology helps bring electricity to developing nations
America leads the world in power transmission technology due to the development of microprocessor relays
By Wayne Beaty,
Power Delivery Editor
In the 1980s, American manufacturers turned to developing nations for low cost labor. As these countries` economies grew from their new international business growth, the leaders of these nations started shopping for more technology.
“America leads the world in power transmission technology due largely to the development of microprocessor relays and programmable logic controllers (PLCs),” said Wally Womack, Burns & McDonnell Transmission and Distribution (T&D) division vice president and general manager.
“PLCs are intelligent electronic devises that replace the electrical mechanical relays,” said Keith Jeffers T&D engineer, Burns & McDonnell, headquartered in Kansas City, Mo.
“They have the ability to communicate externally. With the development of PLCs, we can now develop logic metering, event recording and remote control. The bottom line is they are low cost, extremely flexible and so compact you can hold them in your hand. And when they break down, you don`t have to be there to fix them,” said Jeffers.
Steve Rodick, T&D assistant department manager, said, “We will see this technology grow in the electric utility and substation business, in the developing countries, faster than it will develop in the United States.”
“The reasons,” said Jeffers, “are that they don`t have to duplicate 1930s to 1970s technology. The third world can make the leap into the `90s technology for less cost than the old hard wiring technology. This leap in technology will bring many developing countries into a favorable position for competing in the `90s.
Technologies used by developing countries are not limited to electronic devices but will include others such as transmission line design.
Burns & McDonnell engineers, assigned to design a 90-mile 115-KV transmission line through the swamps, jungles and mountain terrain of Belize (formerly British Honduras) found that the gap between American power technology and the development of Belize, said Rodick, was very evident.
Burns & McDonnell and its construction partner, Irby Construction, won the transmission line portion of the power project in Belize.
The Chinese Government won the Belize power plant project bid. The two worked closely to tie the technology together on this project.
Technically, the problems of stringing power lines across 90 miles of Belize were relatively easy, according to Burns & McDonnell engineers.
“The severest technical problem was securing the poles in the 20-mile wide strip of coastal marshlands. These poles must be able to withstand 150 mile-per-hour hurricane winds,” said Dr. S.L. Yan, Burns & McDonnell soil scientist.
It was Hurricane Hattie that forced the Belize government to change its capital city from the coastal town of Belize City to Belmopan, 50 miles inland. The new inland hydro power plant built by the Chinese is situated in the Belize rain forest near the Guatemalan border.
The power transmission lines would link the generator to the two largest Belize cities, giving both of them affordable power to attract more tourists and industry.
Until now, electricity in Belize has been three times as expensive as electricity in the United States. Businesses were the largest users. Restaurants were illuminated by one or two 30-watt bulbs or an occasional fluorescent light.
Located due south of the Yucatan Peninsula, Belize covers 9,000 square miles and is about the size of Massachusetts. Belize is known for its turquoise-blue waters and its Bay of Chetumal, where hundreds of tiny islands called cayes rise up between the coast and the country`s colorful 180-mile coral barrier reef. Snorkeling, scuba diving and fishing opportunities in Belize are among the best in the world and serve as the country`s major attraction.
Roads are rare in much of Belize. Rivers still serve as major highways. Inland, the flatlands give way to the rugged mountainous cayo district, honeycombed with caves, clear flowing rivers, waterfalls and miles of lush tropical forest. This is the home to many rare birds and the world`s only jaguar preserve.
The challenges for transferring new technology to Belize were not uncommon to other international power projects. The first challenge was the soft coastal soil. A single blow of a hammer in the soft Belize coastal soil caused a soil rod to disappear out of sight. Soft bedrock begins 20 feet below the marshy surface.
Because of the soil, engineers decided against steel transmission towers because the cost of the foundations to prevent them from sinking out of sight or being toppled by 150 mile-per-hour hurricane winds was prohibitive.
Instead, they recommended 55- to 80-foot wood H-frame poles for much of the 90-mile stretch from the Chinese hydro plant on the Macal River to Belize City on the Caribbean coast.
“Modern soil testing equipment and expertise were not available in Belize,” said Rodick, project engineer. “A testing program was designed to define the engineering properties of the soils. Irby installed several pole stubs and screw anchors in various soil types. These were loaded and tested for compression and tension. Their deflections and failing loads were recorded. These data gave geotechnical engineers the needed soil properties.”
In order to secure the H-frame structures against the 150 mile-per-hour gales, three screw anchors were used on each pole of the H-frame. Some screw anchors were embedded in 1.5-2.0 feet of bedrock.
“As the terrain gradually turned to foothills and rock formations, the poles were direct buried. Anchors for corner and dead-end structures were either screw anchors, log anchors or rock anchors depending on the soils encountered,” said Rodick.
“Frequent changes to the locations of the transmission line structure locations were required by the local authorities. Frequent transmissions of survey revisions, from the local surveyor and design revisions to Irby Construction kept our facsimile machine busy,” said Mike Collins, project engineer. “We often turned around design revisions and updated lists of materials in the same day.”
With the help of today`s computer technology, these changes usually take a day of redesigning the project each time the right-of-way changed.
Had the redesigns been done the old fashioned way, by hand, each change could have taken days or weeks.
Another challenge involved laborers. Irby Construction shipped all the materials and equipment required to build the transmission lines by ship from the United States to Belize. Irby hired mostly Belizian construction workers to help the local economy.
Some international projects are simple turnkey jobs. For example, Burns & McDonnell was recently hired by the Malaysian government to review technical proposals for a new 500-kV transmission project for a third opinion.
The Chinese wanted to bring America`s latest microprocessor and PLC technology and more complex high voltage substations into its emerging electrical system.
All the civil engineering and construction for the Chinese project will be done by the Chinese. This project will be a model rural electric substation that will be duplicated throughout China.
“American engineering dominates the world market in microprocessor relays,” said Jeffers. “In developing countries looking for new technology, bottom line cost of this technology and their reliability make them a natural purchase. Why buy mechanical relays and use hard wiring which is more complicated, is more costly, and is harder to fix?” asked Jeffers.
“As is most often the case with technology, the price stabilizes or decreases after development,” Womack said. “That`s what`s happening in the microprocessor market. And the new equipment is more refined, improved, tested and implemented in an increasing number of ways with an increasing ability of functions. The prices range from $3,500 to $14,000. Considering the versatility of the units, it`s cost-effective when you consider the equivalent electrical mechanical system can cost from 50 percent to 200 percent more.”
According to Womack and Jeffers, eventually the microprocessor will evolve into a central computer system controlling an entire substation. With a human interface and a few simple buttons, the system will be able to run logs of recordings, check fault locations, and monitor revenue metering values. It will be able to tailor each application to a particular customer`s needs framework. If a customer changes his mind on what he wants to accomplish, there is no ripping out wires and starting over.
“The beauty of microprocessor technology is that it fits perfectly with the new fiber optics technology. It is now possible to network vast communications systems fast and reliably. The developing nations will be able to capitalize on this new technology first because they have the money in hand and they are not waiting for 1960s or 1970s technology to wear out,” said Jeffers.
Belize, Malaysia, China and other developing nations will be shopping for power, transmission and distribution technology before they get roads and the industry to use them. Power will lead to roads and industry.
Development of microprocessors
Two major manufacturers–General Electric and Westinghouse–dominated the electro-mechanical industry for 90 years.
The introduction of the microprocessor relay witnessed an influx of new competitors. Schweitzer Engineering Laboratories Inc.`s, Pullman, Wash., USA, founder created a revolution in the business. Others, large and small, are rapidly introducing new discrete microprocessor relays. Competition is fierce and a weakness in the microprocessor industry is that there are no established standards. A serious examination of the application of the microprocessor relay is necessary to comprehend the major features involved in its implementation. This examination encompasses the why and how questions and the benefits of this innovative method of protective relaying.
The benefits of the microprocessor relay include:
– lower costs than electro-mechanical relays,
– fault-location capability with local and remote reporting,
– space saving (switchboard and control building),
– event-recording capability with local, remote reporting,
– reliable, with self-checking capability,
– flexible applications, both in program and
– protection capability,
– short delivery time,
– simple panel layout,
– simple wiring,
– simple setting process, and
– reduced engineering and drafting requirements.
In 1984, Blue Ridge Electric Membership Corp., Lenior, N.C., USA, experimented with microprocessor relays as an alternative to electromagnetic backup. Employed as a 230-kV step-distance backup to an electro-mechanical directional comparison blocking (DCB) scheme, microprocessors were also used as the primary step-distance relay on the 95-kV transmission line system. Two technicians learned the operation and maintenance of these schemes in two weeks. It appeared in this case that the engineering level of involvement in the procurement process was reinforced in the rapid adaption by the relay technicians.
When major developers of a geothermal power plant in the Imperial Valley contracted to deliver power to Southern California Edison Co., the Imperial Irrigation District (IID), Imperial, Calif., USA, had to provide the transmission facilities to deliver that power. The 230-kV transmission line project was protected by nine terminals of primary permissive overreaching transfer trip (POTT) schemes using microprocessor relays. The six radial 92-kV transmission line terminals used microprocessor-based primary step-distance and directional ground-overcurrent relays. All 230-kV and 92-kV lines used conventional electro-mechanical backup relaying. Irby Construction Co., Jackson, Miss., USA, reported that the change requiring electro-mechanical backup relaying versus backup microprocessor relaying added more that 20 feet to the length of one control building.
Compatibility was proven as two microprocessors were designed and implemented within one operating substation. The G.E.C. Quadramho was installed on the 230-kV line as the primary relay in a POTT scheme, with an electro-mechanical step-distance backup. A Schweitzer designed SEL-121G also was implemented for its fault-location capability on the same 230-kV line. The fault-location feature is an intrinsic benefit and over the past two years has shown fault locations accurately.
Remote communication by modem, RS 232C switching ports, telephone and IID`s new system-wide micro-wave system allowed access to its relay engineer`s desk in El Centro, Calif., USA, and to the consulting engineer`s desk in Kansas City, Mo., USA. Gulf Western Electric, a Baton Rouge, La., USA, testing firm, performed microprocessor-based relay testing in the field, converting past electro-mechanical testing methods to microprocessor methodology within two weeks.
The metering, event-reporting and fault-analysis tools of the microprocessor relays proved invaluable at startup time. The relay engineer working closely with the testing personnel was able to confirm power flows, phase angles and trends, then check this data against switchboard meters, phase-angle meter readings and supervisory control and data acquisition (SCADA) transducer outputs. In this application, any discrepancy in reading proved later that the microprocessor was more accurate than any other data available. A hard copy generated by the printer in the substation control building aided the energization process.
IID relay application engineers immediately began using the microprocessor-based relays on new transmission applications and old relay replacement programs. IID, like other utilities, learned that replacement of old troublesome balanced-beam electro-mechanical impedance relays could be done on existing relay switchboards with less cost than two new electro-mechanical impedance relays. With the third-zone impedance, timing, directional ground over-current features of the microprocessor-based relay, the entire obsolete line-relaying package could be replaced easily and economically.
This activity also has been reported by the Board of Public Utilities of Kansas City, Kan., USA, and the Central Electric Power Cooperative, Jefferson City, Mo., USA. In these cases, the microprocessor relay was placed in one of the panel holes vacated by four previous electro-mechanical relays.
More recently, the microprocessor was used to fit a 92-kV transmission and 13.2-kV distribution system for IID. The 92-kV line predominantly was protected by a primary electro-mechanical pilot-wire method. The Schweitzer SEL-121G was employed as a backup step-distance with directional ground overcurrent. The microprocessor technology was capable of providing remote fault location and event-recording features not available in the primary scheme.
Once IID gained experience in the 230-kV levels with microprocessor relaying, similar technology was used in transformer and 12.2-kV distribution protection. Asea Brown Boveri`s (ABB) microprocessor distribution protective unit (DPU) was applied as 12.2-kV feeder relays in conjunction with the schweitzer SEL-167. In this case, both the DPU and the SEL-167 offer combined strengths. Either serves as primary/secondary relaying, reclosing and event recording. One provides fault location while the other offers front-keyboard access, spring charge and trip-coil monitoring. In this case, each relay system complemented the other.
Since the most critical and most expensive item in the substation is the station transformer, three different microprocessor schemes were applied at various IID sites. In all three cases, the low-voltage side was equipped with either an ABB RACID, ABB IMPRS or Schweitzer SEL-167. The ascending levels of monitoring not only provided event recording for analysis of fault magnitudes, but served as the low-side backup or main-breaker relay-protection scheme. Yet, conservative practices applied conventional electro-mechanical transformer-differential and high-side backup overcurrent relays.
A 1988 project for Lincoln Electric System, Lincoln, Neb., USA, provided the opportunity to test the microprocessor`s flexibility and integrity in yet another manner. In this case, the utility had successful previous experience with the microprocessor relays at 1.15-kV level. The critical point in this instance is twofold: There was a much higher voltage of 345 kV and the microprocessor was established at the primary, secondary and tertiary levels.
The primary relay was installed as a directional comparison unblocking (DCUB) system, the secondary as a POTT scheme and the third as a step-distance backup. At the same location, a microprocessor relay was implemented on a 115-kV line as a primary POTT scheme and DCB scheme. An electromechanical step-distance relay remains as backup. Use of the microprocessor in four variant applications (DCUB, DCB, POTT and stepped-distance) at two voltage levels, all at one site, exemplifies its versatility and substantiates its reliability.
The low cost and wide range of applications of the microprocessor relay encompasses the lower-voltage application as well. Willmar Municipal Utilities, Willmar, Minn., USA, operates a 69-kV transmission system. Since the engineering manager had a strong interest in the personal computer-driven system such as computer-aided drafting and SCADA, the conversion to microprocessor relays did not appear to be insurmountable.
Evaluation of the looped 69-kV system determined their best application to be a microprocessor relay-POTT application. The same microprocessor relay was used as a backup stepped-distance scheme. A small control room required a miniature relay switchboard that was possible with the use of microprocessor relays. A small staff required minimal help with learning the techniques. The adjoining utility, United Power Association, Elk River, Minn., USA, which uses the same microprocessor relay, easily accepted the adjacent terminal because of their experience with microprocessor relays.
Microprocessor relays require only 18 percent (480 square inches) of the panel area while a typical electro-mechanical backup package (seven devices) requires 45 percent (1,210 square inches) of the panel total area of 2,700 square inches.
Examination shows that a vertical-mounted microprocessor relay would fit in the space of one conventional electro-mechanical impedance relay in the case of a replacement installation.
A 1989 study for Rochester Public Utility Deptartment, Rochester, Minn., USA, demonstrates the impact of space savings. Replacing a 115-kV with a new 161-kV substation on the same site required three new 161-kV line backup relay schemes.
The electro-mechanical panel layout required a costly 20-foot brick control-building extension that would have blocked the required 161-kV ring-bus construction space. An application of the Schweitzer SEL-121F relay and associated DTA metering display unit saved space. In addition, its reclosing, metering and synchronizing capability made it possible to install three line terminals in a 6-foot space, eliminating the necessity for the control-building extension.
The savings of the control-building expansion not only met the site space restriction, but funded the new relay board purchases.
The owner also gained replacement of 40-year-old electro-mechanical relays and gained fault locating, event recording and combined metering-transducer package, all in one microprocessor relay application.
Microprocessor relay space savings
At IID, a skid-mounted, prewired control building (14 feet by 25 feet) manufactured by Electrical Power Products, Des Moines, Iowa, USA, was possible for Carrson Substation by microprocessor relay space savings.
Fundamentally, the microprocessor relay is superlative to any previous methodology. The system usually operated on a single power supply.
If the supply is shut down, the whole system is down. Similarly, nonintegrated electro-mechanical units may also trip upon the failure of one of the other components. Yet, the drawbacks to the relay can be overlooked because there is a backup, an electro-mechanical or microprocessor, and the microprocessor`s intrinsic self-diagnosis reporting alerts the utility that a malfunction must be resolved.
Certainly, the microprocessor is not cost prohibitive. As is usually the case with technology, the price stabilized or decreases after development, then further as equipment is refined, improved, tested, implemented and marketed competitively.
The computer era is making a marked impression on the microprocessor relay business. Experts concur that eventually the microprocessor will evolve into a central computer system controlling an entire substation.
The manufacturers currently producing microprocessors will be constantly expanding product development, and the competition for customer acceptance will intensify. A revolution is changing the face of the industry and many are fortunate to participate and witness its evolution.
Figure 1. Building new transmission lines in Belize is not an easy task. Wood H-frame structures were used because the soil conditions did not lend themselves to steel structures.
Figure 2. Transmission structures must withstand hurricane-force winds of up to 155 miles per hour. Wood H-frame structures were used in this 90-mile line to Belize City.