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Issue 40 - December 2002
HYBRID GENERATOR GROUNDING: WHAT, WHY, HOW WHAT: Generators have traditionally been grounded using two methods: high-resistance grounding and low-resistance grounding. In low-resistance grounding, the neutral of the generator is grounded through a grounding resistor that is usually selected to limit the generator ground current to 200-400 Amps. This provides sufficient ground current for proper system relay operation for all operating configurations. Low-resistance grounding is generally used when the generating unit is connected to a bus that supplies system load. This is a common condition on industrial and commercial power systems such as petro-chemical and paper plants, but is also not uncommon on older utility systems.
High-resistance grounding utilizes a grounding transformer with a secondary neutral resistor to ground the generator. The secondary resistor is reflected through the square of the turn's ratio to provide a high resistance between the generator neutral and ground. This typically limits the maximum ground fault current to less than 10 Amps. High-resistance grounding is universally used to ground generators that are unit connected-i.e., connected directly to a generator step-up transformer. Hybrid generator grounding combines both high and low resistance grounding, with both grounding methods operating in parallel as illustrated in Figure1. WHY: The driving force in the industry to explore hybrid grounding was the substantial damage occurring to older, 20 to 60 MW low resistance-grounded generators in the pulp and paper industry that were sustaining stator ground faults. These generators were protected to the standards recommended in IEEE guides (C37.102 and the IAS Buff Book) and still sustained major burning of the generator stator iron resulting in very costly repairs and long outage times. In one case, the stator windings were burned over 8 inches. The core steel was also burned, requiring it to be replaced. The restacking of the steel core could only be accomplished by removing the stator and shipping it to the manufacturer's plant. The generator rotor was also damaged due to splattered copper and heat from the stator fault. This required the rotor to be shipped off-site to a service repair shop. The total cost to rebuild the stator core, rewind the stator, and rewind the field was 1.5 million dollars. Also, since the ability to repair generators on site has diminished over the years, the cost to ship the generator off-site for repairs contributed another $500,000 to the repair cost. The cost of replacement power and higher demand charges during the repairs were also substantial. In the word of the insurance company's engineer, "Everything worked as planned and then we had a disaster." To address this reoccurring industry problem, an IEEE Working Group within the IAS Industrial and Commercial Protection Committee was formed. The group held its first meeting in 1997 and reported its findings in a series of four IEEE papers that were presented at the October 2002 IAS General Meeting in Pittsburgh. These papers may be purchased from the IEEE. The most significant findings of the Working Group are:
HOW: One of the most important findings of the Working Group was that major damage to the generator due to a stator ground fault occurs after the generator has been tripped. Figure 2 shows how this damage occurs. For a stator ground fault, the 87GD (ground differential protection) provides sensitive and high-speed detection. In some cases, the generator 87G (phase differential) will also operate depending on the magnitude of the ground fault. Both these relays trip at high speed for stator ground faults and initiate the shutdown of the generator by simultaneously tripping the generator breaker, the field and the turbine. When the generator breaker opens, the system component of ground fault current goes to zero. This typically occurs in approximately 0.1 seconds. The generator component of ground fault current continues to flow after the tripping. The generator ground fault current cannot be "turned off" instantaneously because of the stored energy in the rotating machine. The flow of damaging generator ground current will continue for several seconds after the generator has tripped; the exact time is determined by the generator field circuit time constant. It is this slow decaying ground current that does the majority of damage to the generator. A number of schemes for grounding industrial generators are discussed in the IAS papers that reduce generator ground fault current. Most have technical or economic drawbacks. The most promising and practical is the hybrid grounding scheme illustrated in Figure 1. Under normal operating conditions, both generator ground sources are operated in parallel. For ground faults on the industrial system, the ground fault contribution from the generator will be almost entirely from the low resistance (200-400Amp) source. This provides the required level of system ground current for proper system ground relay operation, allowing the generator to supply local load when the utility system is unavailable-i.e., when breakers A and B in Figure 1 are open. When there is a ground fault in the generator stator windings or associated bus connections to the generator breaker, the ground (87GD) and possibly the phase (87G) differentials will operate to initiate a high-speed generator shutdown. As part of the shutdown, the ground interruption device in series with the low-resistance ground path is tripped, disconnecting the low resistance ground source. This reduces ground current from 200 to 400 Amps to less than 10 Amps during the coast-down period, greatly reducing ground fault damage. It is important when hybrid grounding schemes are used that ground differential (87GD) be installed to provide sensitive, selective and high-speed stator ground fault detection. Also, a neutral overvoltage relay (59N) is required to provide ground fault detection during high resistance-grounded generator operation. The first installation of the hybrid scheme has recently been put into service on a 40 MVA generator at a pulp and paper mill in Maryland. Interested? For more information, contact Beckwith Electric at (727) 544-2326 or e-mail at marketing@beckwithelectric.com.
Newton-Evans Research Company recently ranked Beckwith Electric as #1 provider for High Voltage Generator Protection in the North American market. The survey results are from a mid-2002 sampling of 79 worldwide utility relay engineers and managers of systems protection and control. The survey base represents 19% of the utility market and 14.9% of the total generating capacity. The complete study can be found in Volume V of the Worldwide Study of the Protective Relay Marketplace in Electric Utilities: 2002-2005. Newton-Evans is a business-to-business survey research firm, providing business-consulting services for clients in the computer, communications, control systems and engineered products areas.
BlueJay Wireless Data Transceivers Receive FCC Certification
These certifications are extremely important in gaining market and client acceptance of wireless devices in the industry. The next step for our BlueJay line is getting the approved units into actual field applications (beta test sites) with our most important customers to show the strengths of the Beckwith devices in comparison to other technologies that are emerging in the energy market. With over 40% of energy companies rating application integration as a technology investment that is critical to their business, as well as wireless technology, our new wireless products are effective and timely-and keeping with the technological investment that utility companies are projecting and making. The future is bright for this technology and Beckwith Electric is once again leading the industry with real-world solutions.
Beckwith's 4th Annual Relay Seminar Beckwith Electric's fourth annual, Relay Seminar was held October 6-11 in Largo, Florida. The intensive seminar covered crucial aspects of generator, power plant transformer and intertie protection-addressing the practices, methods, and industry standards utilized to provide the electrical protection of power transformers and generators. Over 40 participants from North and South America and Europe attended the seminar. The instructors were Charles Mozina, Applications Manager for Protection Products and Systems; Wayne Hartmann, Manager for Application Engineering, Protection and Protection Systems; and Scott Cooper, Quality Assurance Supervisor and Manager. Inside Sales Specialist, Rachael Herrera, provided support and information on software applications. Plans for Beckwith Electric's next relay seminar, scheduled for fall 2003, are already underway. To be notified of seminar details, sign up for our mailing list at www.beckwithelectric.com.
The tutorial stressed that digital relaying is an interdisciplinary subject that draws from digital hardware, software engineering, power system protective relaying, digital signal processing, estimation theory, and communication links and systems. Dr. Yalla is Vice President of Engineering / Research and Development for Beckwith Electric. He is a senior member of the IEEE and active in the IEEE Power System Relaying Committee (PSRC) for the past 10 years. He is a member of several working groups in PSRC and presently chairs the Working Group that is revising the IEEE Standard C37.90.102 "Guide for AC Generator Protection." He chaired the Working Group, "Application of Multifunction Generator Protection Systems," of the Rotating Machinery Protection Subcommittee of the PSRC. Dr. Yalla also chaired the PSRC Communications Subcommittee Working Group on "Application of Peer-to-Peer Communications for Protective Relaying." He co-authored an IEEE PES tutorial on the "Protection of Synchronous Generators."
Keeping Ahead: The Latest in Beckwith Control Features At Beckwith Electric, we continually upgrade and improve our products while introducing new products to meet the needs of the utility industry. Here are some recent improvements and additions to our transformer LTC and regulator voltage controls. Features
This is the industry's first palmtop communication program to allow complete data monitoring and download, setpoint & configuration reading and changes and remote control by palmtop computer. No more need to carry a large laptop and attempt to read the screen under adverse viewing conditions. Plus, software is free to all customers!
This ΔVAR -2 paralleling option allows two transformers to be paralleled without the connection of the "current balancing module" previously required for all circulating current paralleling. There is no longer any need for auxiliary CT's to match unequal impedance transformers. This feature also includes the ability to operate correctly with separate high-side sources. Extremely simple interconnections reduce field/installation problems while saving money.
We have added a cumulative and resettable monitor which accumulates the number of tapchanges for each tap position. This knowledge allows more informed decisions for maintenance timing on tapchangers.
Illustrated here, we have added the ability to preview the odd voltage and current harmonics as a function of % of fundamental out to the 31st harmonic.
The M-2001B is up-to-date with all on-board protocols in general use in the industry. The M-2001B has on-board: BECO 2200, 2179, DNP-3.0, UCA-2, & MODBUS protocols. Combined with the COM2 RS-232 port (located on the front of the unit)
and the COM1 RS-232, RS-485 and Fiber Optic ports (located on the top
of the unit), the M-2001B becomes the most versatile and usable communicating
control in the industry.
The M-2001B's ability to log data is unequalled in the industry. With 13 programmable quantities to log and a large record capacity, it is possible to designate a loop-of-data from approximately 1 week to 1 year. Illustrated here is the setup screen for the data logger function.
Note: All these features are also included in the GE-2011 control. Beckwith Electric supplies GE with the M-2001B Tapchanger Control under the name GE-2011. We have created a training module which introduces the M-2001B; it is available on our web site and consists of images and narration. This module goes through the basics of the M-2001B including features, installation, setting, and main software screens. The technology behind the module is Flash animation. You will need to have the free Flash plug-in installed. If you are operating Internet Explorer 5.0 or Netscape 5.0, you already have the plug-in. Directions for downloading the plug-in are available on our site. You may by visiting www.beckwithelectric.com and following the link to the M-2001B page from the Products & Solutions section, then click on the link for the introduction to M-2001B under Online Learning Center.
Product Quality Validation Group - Update Beckwith Electric's Product Quality Validation Group performs a valuable job-that of ensuring every design performs not only what its specifications detail, but also what the customers want and expect from it. The group conducts an extensive battery of tests on each new and updated product that the Research and Development team creates.
Since the group's primary responsibility is to ensure that all products meet their functional specifications and customer expectations, they perform functional and hardware tests designed to meet these goals. Environmental testing exposes each unit to extremes in temperature, typically from 80° C to - 40° C. Relays are subjected to various tests with Omicron and AVO test sets which simulate voltages and currents based on users' equipment. The various voltages and currents are then fed into the relay. Many of these tests duplicate those conducted during the design process. Other tests are "what-if" scenarios-conditions to which the equipment may be exposed in the field. Safety of each product, and compliance with various standards such as ANSI, are also evaluated. The entire battery of tests that the group performs can take anywhere from four weeks to eight months. The resulting information from these tests is compiled into hundreds of pages of data that is made available to our customers. One of the group's goals is to make these reports "paperless" by converting them to Adobe PDF files that can be accessible on CD-ROM. Once the product successfully passes all the tests that the Product Quality Validation Group performs, the product can then go into production.
Scott is currently working towards a degree in computer science and information systems. He is a member of IEEE and served in the U.S. Navy for six years in the nuclear reactor controls division. He also attended Naval Nuclear Propulsion Training, the Naval Nuclear Power School; and the Naval Nuclear Field Electronics Technician School. Prior to joining Beckwith Electric, Scott was a senior technician with Seapower Engineering where he engineered, installed and repaired electrical and electronic systems, an inside sales specialist with Aampro Marine Products and an IT Specialist with Hilb, Rogal and Hamilton.
Jim Shanahan, Beckwith Electric's regional sales manager, says of John, "He is one of the most dedicated, most professional people I've had the pleasure of working with. He's a true southern gentleman." John and his wife, Anita, have moved to Georgetown, Texas. He plans to continue his involvement in the industry by conducting a part-time utility sales business from his home. All of us at Beckwith Electric wish him the best of luck!
All New - www.beckwithelectric.com If you've visited the Beckwith Electric Web site recently, you've noticed a few changes. We have redesigned the site and added new features to it. The main navigation menu remains in the same location - on the top of the page - with the same links, plus one for downloading software. We have added side navigation links called "Quick Links" - a listing of popular and important pages on our Web site. In each section, there is an additional list of custom "Links" in the side navigation listing relevant pages. New Features"Software Downloads" - all the software available for download and information for versions not available on the site. Currently, you can find the Autodaptive® Software Suite, the entire family of IPScom software, COMVERT for oscillography records, and TapTalk. "New Solutions from Beckwith Electric" - more information on the latest product offering from us. Once on the New Solutions page, you will find a list of the latest additions to the Web site, both small and large. "Hot Topics" - a listing of the most recent articles on industry trends as well as places to see Beckwith Electric personnel and ways to learn more about our solutions. "eLearning Modules" - the beginnings of the Online Learning
Center. The first two eLearning Modules are available. The one for the
control line is the Flash animation of detailing the features and uses
of the "Document Center" - still contains all the electronic literature available. The documents are grouped by model number (such as M-3410) or product category (such as DG Interconnection Protection). Once you choose a model number or product category, you will find all the books, guides, and papers related to your choice. We also have an archive of instruction books for models that are no longer being manufactured. Product Pages - contain all the links, documents, and information related to that product. The best way to reach a product page is to click on Products & Solutions, then choose the model number from the drop-down list. "Products & Solutions" - will provide you with current information on implementing our products. Interested in volt/VAr management? Click on the link for Autodaptive products and learn about the latest in technology for controls. As always, you can join our mailing list by clicking on the link to subscribe.
We value your privacy and do not sell our mailing lists. Once you opt-in
to our list, you will receive Powerlines and occasional announcements
on products or events. Please e-mail webmaster@beckwithelectric.com
with questions or comments.
Beckwith Attends Trade Mission for Veracruz Mexico Bob Beckwith, CEO, and Lou Abilock, President, attended a Mexican trade
mission in Tampa, Florida in August. The meetings, hosted by the State
of Veracruz, Mexico, planned ways to expand trade between Veracruz and
Tampa-area businesses. The event brought 60 business leaders and officials
from Veracruz to talk with many businesses and leaders in Tampa for the
three-day trade mission. Beckwith Electric has been serving the power
needs of Latin America since 1969 and plans to continue to offer our quality
products to the growing countries.
Articles from Issue 40, December 2002 of Beckwith Electric's Powerlines. |
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For
the past several months, Beckwith Electric's BlueJay Wireless Data Transceivers
have been undergoing extensive tests with the FCC (Federal Communications
Commission) for emitted and radiated emissions compliance. The Data Transceivers
must comply with levels set for them in the FCC Rules and Regulations,
part 15.247. It is with great pride that we report that testing has been
successfully completed for the United States requirements as well as the
Canadian requirements, and we have received our certifications. The USA
FCC Identifier number is QMCM2911 and the Canadian Technical Acceptance
Certification Number is 4461A-M2911.
Dr.
Murty V.V.S. Yalla presented a tutorial on digital protective relaying
and communications in India in June. Twenty-seven participants attended
the seminar, which was sponsored by the PES/IAS Hyderabad Chapter. 
Mike
Thompson has been named the Product Quality Validation Group supervisor.
As group leader, Mike ensures that those goals are met in a timely manner
and are documented properly to ensure reproducibility. Mike has an extensive
background in the field, having attended a technical school for electronics,
the Naval Nuclear Power School and the Naval Nuclear Field Electronics
Technician "A" School. Mike also worked in the U.S. Navy for
eight years as a Nuclear Reactor Operator, with six of those years on
board a fast-attack nuclear submarine. 
Scott
Cooper has been named Manager of Beckwith Systems Engineering and Customer
Service. Together with Tom Branch and Frank Lau, Scott will be responsible
for growing BSE's business-custom-designed products and systems. Scott
will also supervise the Customer Service Group, which is responsible for
providing field service engineering and facilitating post-sale activities.
Beckwith
Electric would like to salute John Williams' long and illustrious career
as he retires as President of Butler & Land, Inc. Butler & Land
is an electrical industry manufacturers' representative based in Dallas,
Texas. They service Texas, Mississippi, Louisiana, Arkansas, Oklahoma,
and New Mexico with a staff of 21. John started working for the company
in 1974, where he was involved in utility sales. In 1988, he moved from
Vice President to President of the firm. 
