Powerlines - Beckwith Electric Co, Inc. - Services and Products for Electric Power

Tapchanger control applications can be optimized by using a variety of timing options. In most applications, a simple timer of 30 seconds will operate satisfactorily. But in other applications, more sophisticated options are desirable and in some applications, timing options are critical to satisfactory operation. Beckwith Electric tapchanger controls provide many timing options for versatility to obtain the most effective operation-this article explains these options.

The figure illustrates a voltage control typically set with a setpoint of 120 V (the voltage target) and a bandwidth of 2 V (the leeway given the voltage before we take action to correct it). This results in an upper bandedge of 121 V (above which we begin timing to an operation), and a lower bandedge of 119 V (below which we begin timing to an operation).

Instantaneous reset or integrating timers
The simplest application, and the one available on all controls including analog, is an instantaneous resetting definite timer. All that the application requires for optimum operation is a definite time outside the bandedges with the timer instantaneously resetting to zero if the voltage reenters the bandwidth before timing out.

The integrating timer option does not instantaneously reset the timer to zero upon reentering the bandwidth, but rather reverses the countdown or timing. In other words, 25 seconds out-of-band followed by 10 seconds in-band results in the timing restarting at 15 seconds instead of zero seconds. The benefit is seen in an application where the voltage is oscillating around the bandedge and the control does not operate the tapchanger. It is much more likely that the integrating timer will operate once and the oscillating voltage will now be well inside the band and closer to the desired voltage level.

Sequential operation, non-sequential operation, inter-tap time delay, or pulsed output
The figure also illustrates the results of the choice between sequential operation, non-sequential operation, inter-tap time delay operation and the pulsed output operation. The green operation path illustrates sequential operation with a large drop in voltage. The voltage remains low until the timer times out (TD-time delay) and the control sends power to the tapchanger mechanism. Since, after the first tapchange (T1), the voltage is still below the bandedge, the power remains on and the tapchanger continues to operate two more steps (T2, T3) until the voltage reaches the bandedge.

Some tapchanger mechanisms require a break in the power flow to the mechanism before taking a second step. Each of the other options provides a break in the raise or lower signal to the tapchanger between tap operations.

The initial solution to the problem was non-sequential operation. This method uses a counter contact to reset the timer to zero between operations resulting in a full timeout between every tapchange. Shown in blue, the total delay time is 90 seconds or three time delays before restoring the voltage to a desirable value.

The next option, also initiated by a counter contact, includes a separate timer that can be set for use between tapchanges after the initial timeout of the main timer. This is an inter-tap time delay option. A typical setting is 5 to 10 seconds which results in arriving at the desired voltage much faster than non-sequential operation. Another application for inter-tap time delay is for paralleled transformers. If several tapchanges are needed and the operating times of the mechanisms are not identical, one transformer could take more tapchanges than another and result in unmatched tap positions. This inter-tap time delay operation is illustrated in yellow in the figure.

Another choice available is a pulsed output. When chosen, the output is a series of distinct adjustable time pulses issued after the initial timer has timed and continuing for as long as the voltage is out of band. A major advantage of the pulsed output is that no counter contact is required to initiate the break in power to the mechanism yet the time to achieving the desired voltage is reduced. Also an individual pulse has been designed to continue until completion-regardless of voltage action. If the voltage returns into band in the middle of the pulse, it will complete. This action solves problems of voltage drop due to motor starting which tends to artificially return a high sensing voltage into the band, thus stopping the tapchange. The operation with pulsed output is illustrated in red.

Definite or inverse time
Another separate timing choice now available is the inverse time characteristic illustrated by the dotted curve. The timeout of the control towards operation will decrease for larger voltage variations whereas the setting time will be effective just outside the bandedge. For example, assuming a bandwidth of 2 V, the time at the bandedge (+/- 1 V) would be the timer setting-say, 30 seconds. At +/- 2 V, the time would be 15 seconds; at +/- 5 V, the time would be 6 seconds and above +/- 10 V, the time would be 3 seconds. This option could be used to assure faster response to wide voltage changes or to possibly reduce the number of tapchanges on a transformer or regulator.

Autodaptive® timing
The latest timing choice is only available in our Autodaptive control line-Autodaptive timing. No timer is actually set; it is an inverse time curve constantly being adjusted automatically as to threshold value and accumulation rate according to the Voltage Regulation Quality Factor (VRQF). Watch for more Autodaptive Control line articles in future Powerlines issues or visit our Web site at www.beckwithelectric.com and click on Products & Solutions for more information on this unique timing option.

Will Miller's accomplishments are varied and worldwide. He has been a public school teacher, has worked for Honeywell, Inc. and Sciences Applications International Corp. (SAIC), and is a decorated Vietnam War veteran. In 1989, he was voluntarily recalled to active Navy duty to augment the Depar™ent of Defense (DoD) Current Operations Staff (J3) at U.S. Atlantic Command in Norfolk, VA. He has served as DoD Civil Service Program Analyst/Technology Support Specialist, and has worked with U.S. Army Southern Command, U.S. Space Command, and many other military agencies and related companies. His project experience includes program and financial analysis for multi-million-dollar DoD operations, nuclear, natural, & technological disaster mitigation, WW-III Contingencies, Space Warfare, and contingency support. In the Defense Depar™ent, he was a member of the American Society of Military Comptrollers, and was knighted in the Sovereign Military order of the Temple of Jerusalem (Knights Templars), the oldest military knighthood.

Mr. Miller has a strong record of public service including serving on the Board of Directors of the American Red Cross, Tidewater Virginia Chapter, and serving as Chairman of its Disaster Services Committee. He has volunteered many hours of support for Public Television, served in the Lions Clubs International, served as Committee Chairman in the Virginia Education Association (VEA) and been a lobbyist for both VEA and the National Education Association (NEA) influencing state and national education policy.

He is founder and president of a high-technology company providing technology support, preventive and predictive maintenance consulting, and AMSOIL long-life/wear-reducing synthetic lubricants for industry, automotive, and marine interests. He resides in Belleair Bluffs, Florida with his wife, Gray, who is Assistant Director of School Food Service for Pinellas County Schools. Their daughter is a special education teacher in Hillsborough County Schools in Florida, and their son, a former Marine, works for Boeing Corp. in North Carolina. The Millers have two adopted greyhounds.

Protection of Pumped Storage Units with Beckwith Multifunction Digital Relays

Protecting pumped storage units provides the relay engineer with some unique protection considerations. The use of multifunction digital relays requires careful attention to delineating primary and backup zones, as well as to maintaining the proper phase currents and voltages to protection relays for both the generating and motor pumping operating modes. This article highlights these considerations.

The purpose of a pumped storage hydro installation is to store energy during off-peak periods to be used for generation during peak demand periods. Water is pumped from a lower reservoir to an upper reservoir where it is stored to be used later to generate electricity. Most pumped storage units are designed for reversible operation, rotating in one direction as a turbine/generator and in the other as a motor/pump. Reversal of direction is accomplished by reversing the phase sequence of the main electrical leads.

The requirement to accommodate reverse-phase rotation introduces major differences in protection between pumped storage and conventional hydro units. One of the major problems encountered is in maintaining the proper CT (current transformer) and VT (voltage transformer) connections for correct operation of the associated protective devices when the generator/motor phases are reversed. When a reversing switch is used for generator/motor phase reversal, auxiliary contacts of that switch are necessary to shift the connections of the effected CT and VT transformer secondary windings. Note that the phase reversal only involves one set of CT's.

There are several important considerations in applying protection to pumped storage units:

The last consideration is particularly important. During startup in the pumping mode, frequency can go from 0 to 60 Hz. Figure 1 illustrates the use of the Beckwith Electric M-3425 Generator Protection relay, M-3520 Intertie Protection relay and M-3310 Transformer Protection relay to provide protection for a typical pump storage unit. Primary and backup relays are used to provide protection for a hardware platform failure, which could result in the loss of all protective functions within a given relay. Some functions within the M-3425 relays are in-service only in the motor/pump mode and switching can easily be accomplished using the M-3425 programmable inputs. Some special application considerations of standard M-3425 functions for pump storage units are listed in the table.

24	V/Hz protection must operate at low frequency (10 Hz) to provide overexcitation protection during start-up.
27TN	The level of neutral third harmonic should be measured to ensure adequate level for proper application in both the pump and generator mode. Application may have to be restricted to only the generator mode.
32	Under power (low forward power) can be used to detect loss of incoming power during pumping.
40	If the unit is started as an induction motor, the loss of excitation relay should be armed only after the field breaker is closed and the unit is synchronized to the system.
47G, 47M	Phase sequence voltage relay (M-3520) can verify the presence of correct phase rotation of the machine in the generator and pump mode.
50/27	Inadvertent energizing must be disabled during starting in the pump mode.
51T	Lock rotor protection during operation in motor mode.
81G	As an overfrequency relay, this function can provide backup for overspeed in the generating mode.
81M	Underfrequency relay in pump mode can also be used to provide the first step in underfrequency load shedding program.

There are several significant advantages of using digital technology to protect pumped storage units rather than using electromechanical/static relays. These advantages include:

Reduced Panel Space - Figure 2 illustrates a panel layout for a typical pumped storage unit using only two NEMA-12 cabinets for GSU (generator startup) and generator protection.

Lower Cost - the installed cost-per-relay function is substantially lower than for electromechanical/static relay protection

Programmable Logic - the use of programmable inputs allows the software to switch relay setpoints between generator and pump mode-greatly reducing the external wiring. Beckwith Electric relays have multiple setpoints for most relay functions that can be switched. A simple click of the mouse can set up this logic using Beckwith Electric's IPScom® Communications Software. Multiple setting groups, used by some manufacturers, can also change settings from generator to pump mode but typically can't reverse the phases of only one set of CT's to avoid using current reversing contacts in the CT circuit.

Low Frequency Relay Response - Beckwith Electric's unique algorithms allow operation of key relay functions at extremely low (10 Hz) frequencies, providing protection during pump start-up. Some manufacturers use frequency tracking which cuts off at about 30 Hz, making most functions in the relay inoperative for frequencies below this level.

Independent CT Inputs - the independence of CT inputs allows Beckwith Electric relays to maximize the use of limited CT inputs in upgrading older generators where the addition of new CT's is cost-prohibitive. Figure 1 illustrates this point. The CT's in the generator neutral are used to supply both the generator differential (87), as well as the overall differential (87T overall) neutral inputs. Current inputs to Beckwith Electric relays are not tied together within the relay, thus allowing more flexibility in application than many competitors' relays.

Other important digital relay features include self-diagnostics, communications capability (RS-232 and RS-485 ports) and oscillographic monitoring. The major shortcoming of the technology is the reduced redundancy due to many functions residing on a common hardware platform. The use of dual relays and careful attention to primary and backup protective zones effectively address this issue, as illustrated in Figure 1. Sufficient redundancy can be economically provided such that the failure of a single relay will not require the generator to be removed from service.

Interested? For more information, contact Beckwith Electric at (727) 544-2326 or e-mail at marketing@beckwithelectric.com.

A Beckwith Electric technical paper entitled "Interconnection Protection of IPP Generators at Commercial/Industrial Facilities" has been selected to receive the 2000 Prize Paper Award for the IEEE/IAS/I&CPS Power Systems Protection Committee. The award will be presented to Chuck Mozina, author of the paper, at the 2001 I&CPS Technical Conference Awards luncheon on May 16, in New Orleans.

Beckwith Electric will be holding a technical session on control applications in conjunction with the ECNE's (Electric Council of New England) spring meeting. The session will be held Wednesday, March 28, 2001 at the Crowne Plaza Hotel in Nashua, New Hampshire. The session begins at 9:30 a.m. and will include lunch. There is no cost to attend this session. Tom Jauch, Manager of Application Engineering for Controls and Control Systems, will be conducting the session. Topics will include:

Basic Transformer LTC/Regulator Voltage Controls
Basic settings & operations, line drop compensation (LDC), first house protection, backup controls, cascade operation, reverse power flow operation

Transformer Paralleling
Basic needs, parallel balancing, circulating current method, line drop compensation effects, multiple transformers, dissimilar transformers, limitations, Delta/VAr Systems

Digital Universal Voltage Control
New features, data logging capabilities, manual settings, software features and use

Controls with Developing Technology
Basic system VAr needs, conventional capacitor controls, Autodaptive® Capacitor Control (ACC), operational results, Autodaptive Tapchanger Controls (ATC/ARC)

Interested? For more information, contact Beckwith Electric at (727) 544-2326 or e-mail at marketing@beckwithelectric.com.

Laurie Tudor has been appointed Controller and Treasurer of Beckwith Electric. In making the announcement, Lou Abilock, President of Beckwith Electric, expressed, "Laurie will be instrumental in leading the company to its next level of financial growth during the next decade."

Laurie provides financial support to all areas of the company. She earned her BA in Accounting from the University of South Florida and was hired by Beckwith Electric as a staff accountant in 1985. She recently completed the Certified Management Accountant Certification Examination (CMA). In addition, Laurie is a member of the National Association of Contingency Planners and is a member of Beckwith Electric's Disaster Recovery Team.

Interested? For more information, contact Beckwith Electric at (727) 544-2326 or e-mail at marketing@beckwithelectric.com.

Beckwith Electric's Web site has had several additions to its list of products and its Document Center in the past few months. Among the new items for you to download are a reprint of the latest technical article, Protecting Dispersed Generators Using Digital Interconnection Technology, written by Chuck Mozina and printed in the November 2000 issue of the EGSA' s ON PEAK Performance Consulting/Specifying Engineer supplement. We have added an instruction book for the M-2001B Digital Tapchanger Control plus an updated specification sheet, in English and Spanish, that includes details on the DVAR^™ Paralleling Method as a new added feature. The M-0121/M-0169 Auxiliary Current Transformer Units specification sheet is new on the Web site. Also new are specification sheets for the M-0174 Replacement Panel for replacing the Moloney/Tempo LTC Control Panel, M-2299 Adapter Panel for replacing the Toshiba TB-R800 Regulators, and the M-2920A BecoEye® Infrared Communications Adapter for use with the M-2501 and M-2501A Autodaptive® Capacitor Controls. Specification sheets for the M-0188 Syncrocloser® Check Relay, M-2025 Current Loop Interface Module, M-2029 TapTalk® Communications Software, and all Integrated Protection Systems® have been updated to show 2001 features and options. The M-3310 and M-3520 specification sheets come in Spanish too. Our first application guides are available for you to download from the Document Center-ones for the M-2050 Surface Mounting Kit and M-2299 Adapter Panel.

In the Product Support and Software Downloads section, you will find the M-2803 BlincIR® v9 software. The software was field tested under dynamic conditions and is more robust and reliable than previous versions.

A new section continues our dedication to excellent customer service by announcing advisories and service bulletins. Currently, we address an issue involving the M-3425 and recommendations.

Finally, the spokesperson for our Autodaptive® products, Cappy^™, made his first appearance last month to invite viewers to visit our booth at DistribuTECH in San Diego. Cappy hosts online presentations on the Autodaptive line of Controls-his first presentation is an overview of the Autodaptive System. Soon Cappy will be going in-depth and explaining how the controls interact with each other. The Cappy presentations are created with Flash animation and audio. Your browser-Internet Explorer or Netscape-and speakers should be all you need to watch the presentations. You can find Cappy and his presentations on the Autodaptive page under Products.

At Beckwith Electric, we strive to apply the latest technology available, regardless from which market the technology originates. Our latest use of current technology comes with the advent of the Handspring^™ Visor^™ that hails from the consumer handheld and personal digital assistant (PDA) market.

The Handspring Visor is currently being used as the HMI (Human/Machine Interface) for all of Beckwith Electric's Autodaptive® controls. With the Visor as the HMI, utilities no longer need to take laptops into the field. The Visor, loaded with Beckwith's customized software, can not only be used to read metered data from the control, and change setpoints and configurations in the control, but can also be used to download the vast amounts of data being collected by the control. In essence, the Handspring Visor is both an HMI and an electronic briefcase. Currently, the Visor can be used on the following controls:

Beckwith Electric chose the Handspring Visor platform for two reasons. First, the Palm OS is an open architecture operating system. Therefore, the operating code, developmental tools, and support were readily available as simple downloads from Handspring since their founders are the original set of Palm OS developers. Second, the Handspring Visor has the Springboard Expansion Slot that can accommodate all third-party developers' modules designed for the slot, such as an MP3 player or a digital camera.

For these reasons, several hundred third-party developers have created hardware, firmware, and software designed around the Handspring Visor platform. The availability of so many choices to the consumer, sells many, many new Visors for Handspring. This marketing virtually ensures that the platform will remain available in the market for a long time.

Additionally, the ease of use, massive memory (8M onboard), expandability, flexibility, quick programmability, and low cost were more influential factors in the decision to choose the Handspring Visor.

Future uses for the Handspring Visor at Beckwith Electric continue to be evaluated. Check for the latest news on our Web site at www.beckwithelectric.com.

Three people won a Handspring^TM Visor^TM Deluxe handheld computer from Beckwith's business card drawing at the DistribuTECH Conference and Exposition held in San Diego, CA last month. The lucky three are: Jamie Allshouse, with the Public Utilities Dept. for the City of Anaheim, California; Stephen Noe, Manager of System Operations for the Knoxville Utilities Board, Tennessee; Flor Cascio, Distribution Operations Analyst for PEPCO (Potomac Electric Power Company) of Washington, D.C. and Maryland.

The next Handspring^TM Visor^TM will be given away at the TechAdvantage NRECA Conference and Exposition in St. Louis, Missouri, March 9-12. Good luck to all participants!

Articles from Issue 34, March 2001 of Beckwith Electric's Powerlines.
Copyright 2001. All rights reserved. Reproduction of the whole or any part of the contents without written permission is prohibited.

Issue 34 - March 2001