Issue 31 - June 2000

• Advanced Paralleling of LTC Transformers by DVAR^™ Method
• Keeping Current by Bob Beckwith, CEO: Beckwith Electric Research
• New VP of Sales Appointed
• Beckwith Introduces Reinhausen MK20 Control Replacement
• Protection Relay Seminar
• Autodaptive® Volt/VAr Management System Provides Payback
• Technical Support Engineer Appointed
• Literature Available

Advanced Paralleling of LTC Transformers by DVAR™ Method
by Tom Jauch, Manager of Application Engineering for Controls and Control Systems

As a leading authority on paralleling, Beckwith Electric is proud to announce development on the Advanced Paralleling of LTC Transformers by the DVAR™ Method. The DVAR Method is an added feature available on the M-2001B Universal Digital Tapchanger Control. It addresses those transformer paralleling applications where a system condition could exist where:

1. The primary windings of the paralleled transformers might be fed from different source transmission lines.
2. There is a large variation in relative impedances of the paralleled transformers as tap changes occur.
3. There is a special need for some VAr biasing to the voltage level setting.

Paralleling is required to control unequal transformer loading (VAr) due to tap position. Traditionally, there have been three paralleling methods that were commonly followed:

• Master/follower paralleling methods assume that under all system operating configurations the desired objectives of the operation are met by maintaining the same physical tap position on all paralleled transformers. The operation consists of one active control commanding additional transformer tapchangers to follow.

• Circulating current paralleling methods assume that a continuous circulating current path is maintained for all system operating configurations and that any changes in the circulating current path is maintained for all system operating configurations and that any changes in the circulating current magnitude is, in fact, a result of an undesirable change in the relative tap positions of the paralleled transformers. Circulating current methods bias all paralleled controls to operate next in the direction to minimize the circulating current.

• Power factor paralleling methods assume that the most desirable combination of tap positions on paralleled transformers is one that maintains equal power factors in the transformers. This method usually does not bias the controls to operate but blocks the control from operating in the wrong direction based on the power factor. Further, it is difficult to apply power factor methods in substations with more than two transformers in parallel.

The Substation Breaker Arrangement illustration is that of a substation arrangement which can result in the system condition where one of the paralleled transformers can be fed from one transmission line while the other is fed from a separate line. Another arrangement which can result in the same phenomena is that of ring bus arrangements with both line positions and transformer positions. Operational under these configurations can violate the assumptions of each of the three methods described above.

Substation Breaker Arrangement

• A tap difference causes a circulating current (lc)
• IC is calculable from the tap step voltage and transformer impedance
• If C open = Independent operation -- LDC OK
     B or D open = Independent operation -- correction needed
     A open = Parallel operation -- separate sources (DVAR^TM required)
• Ic is mostly VArs since transformer impedances are mostly reactance

Note: kW flows are not effectively controlled by tap position but by relative impedance or phase shifting transformers.

Using these traditional methods, however, can result in undesirable operations for paralleled transformers for three reasons:

1. The transformers must continue their basic function of controlling the load bus voltage as prescribed by the setting on the control.
2. The transformer must act so as to minimize the detrimental current which circulates between them, as would be due to the tapchangers operating on different tap positions.
3. Both above-mentioned points must continue correctly in multiple transformer applications regardless of station breaker operations and resultant station configuration changes.

DVAR Method

To address these conditions, the DVAR method was contrived. The theoretical basis for the DVAR Method of paralleling is that paralleled transformers are meant to share the VAr load (as well as the KW load) of the load bus. Since the KW sharing of the parallel transformers is determined by the relative transformer and system impedances and not the tap position, KW flow should not be able to affect tap position choice. Also, the best choice of loading parallel transformers is to maintain the VAr sharing regardless of KW loading.

The DVAR Method uses all the same auxiliary equipment as the circulating current method—specifically, a parallel balancing module (which separates the load current from the difference current) and an overcurrent relay (which gives independent backup protection to the paralleling operation). This makes it directly replaceable to other controls using circulating current methods. The DVAR Method is optionally incorporated in the Beckwith M-2001B which internally calculates and compares the individual transformer VAr flows to make decisions for parallel biasing and operation.

The D VAR Method will result in the VAr flow to the substation load to be shared in the appropriate ratio by the paralleled transformers. It should be noted that matching auxiliary CT’s are required in traditional circulating current schemes when equally sized transformers with different impedances are paralleled. Those auxiliary CT’s are not necessary when the DVAR Method is used and operational loading is actually improved.

The operational implications and applications of the DVAR algorithms to special transformer applications can be instrumental in the more complex power system of today.

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

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New VP of Sales Appointed

Thomas R. Beckwith was appointed Vice President of Sales for Beckwith Electric Company effective July 15. He will be responsible for developing sales strategies to increase market penetration for the national and international markets and to introduce new products, and also to develop the sales representative networks within the marketplace.

Tom has over thirty years of experience in the power industry, encompassing the fields of sales, management and engineering. His most recent experience includes positions as VP of Sales and Marketing for RFL Electronics in New Jersey, as a consultant for Bectech International and as General Manager of the International Division for Basler Electric. Prior to that, he had worked for Beckwith Electric for over twenty-two years, beginning as a Product Engineer and Production Manager, to later becoming VP of Marketing and President of the engineering services and training division.

Tom has a Bachelor of Science degree in Electrical Engineering from Case Western Reserve University and a Masters of Business Administration (MBA) degree from the University of South Florida. He is a member of IEEE and the Power Systems Relaying Committee and is active in various working groups.

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Beckwith Electric has earned a reputation in the utility industry for easy tapchanger control replacements for both LTC transformers and regulators. Although Beckwith Electric offers a wide selection of direct tapchanger control replacements, sometimes a customer needs a system to suit specific application needs.

Tom Branch, a Senior Project Engineer for BSE (Beckwith Systems Engineering), is responsible for developing system products based on customers' specifications or application needs. These products include direct replacement tapchanger control panels for transformers, complete transformer paralleling systems using the circulating current method or the DVARÔ method, generator synchronizing and control systems, and motor bus transfer systems. Tom comments, "Beckwith continues to add products to its line of transformer and regulator controls to meet customer needs. A prime example is the M-2220 Tapchanger Control."

After several requests for a replacement for the Reinhausen MK20 Control, BSE designed and built the Beckwith M-2220 Adapter Panel. This panel combines with the M-2001B Digital Tapchanger Control to provide convenient, direct mechanical replacement for the Reinhausen control in the existing enclosure. The M-2220 connects easily to the M-2001B Digital Tapchanger Control, using four mounting screws and a 24-pin connector. This panel provides direct mechanical and electrical replacement of the old tapchanger control while using the existing MK20 enclosure as well as providing built-in shorting protection when the M-2001B Tapchanger Control is removed.

Ted Murphy, Sales Specialist for Controls and Control Systems, is Beckwith's contact person for assistance with controls. He can provide pricing information immediately and let you know which controls are available from stock, and can consult with BSE to assist you in identifying an Engineered Product to suit your needs. He may refer you to the Beckwith Electric Quick Reference Guide that describes Beckwith controls that are designed to be direct replacements for existing controls.

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

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Protection Relay Seminar

Beckwith Electric is currently registering attendees for the Beckwith Electric Relay Seminar to be held October 15 - 20, 2000 in Largo, Florida. The registration deadline is September 15, 2000. This year, the seminar has been extended to include four-and-a-half days of intensive training in generator, power plant transformer and intertie protection. This seminar will build the background needed to understand the complex subject of generator, power plant transformer and intertie protection, even for those with a limited knowledge of protective relaying.

Topics to include:

• Fundamentals of Generator and Power Plant Protection
• Protection of Generators Using Microprocessor-Based Technology; Application and Setting of the Beckwith Electric M-3420, M-3430 and
  M-3425 Relays
• Interconnection and Transformer Protection Using Microprocessor Technology; Application and Setting of the Beckwith M-3520 and M-3310 Relays
• Commissioning and Testing of the M-3430, M-3420, M-3425 and
  M-3310 Relays

Those who should attend include utility engineers, consultants (especially those involved in IPP design), equipment/control design engineers, generator set manufacturers and packagers, as well as others who specify and develop settings for the electrical protection of generators and transformers.

Enrollment is limited to 50 participants on a first-come, first-serve basis. The seminar cost is $650 and includes course materials, lunches, morning and afternoon breaks, two dinners and the Sunday evening welcome reception. Deadline for registration is September 15, 2000. All cancellations after September 29 will be charged a 50% processing fee. Substitute attendees are welcome at no additional charge with prior notice.

Chuck Mozina, Manager of Application Engineering for Protection and Protection Systems for Beckwith Electric, and Dr. Murty V.V.S. Yalla, Vice-President of Research and Development/Engineering are the instructors for the seminar.

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

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By Mark Dixon, Manager of Autodaptive® Systems

Utilities all over the country are doing economic evaluations on newly installed equipment to help determine the overall bottom-line effectiveness and to determine the payback and return on investment for their shareholders. Recently, the emphasis has been on the quality of delivered power to the customer and Volt/VAr Management Systems have risen to the forefront. Beckwith Electric has developed an economic evaluation model that approximates the typical financial impact to a utility using an Autodaptive® Volt/VAr Management System. Relatively conservative numbers were used in the calculations of the model to illustrate minimum, credible, evidence of savings and cost reduction. As with any model, individual results vary according to a utility's operating costs, VAr management strategy and the degree to which Autodaptive products are employed. In this model, using all Autodaptive products to comprise the Volt/VAr Management System, the following results were yielded.

In any evaluation, some assumptions must be made when all variables are not quantifiable. In this case, the following assumptions were made.

1. Total system losses = 8%
2. All losses are not reduced by the installation of distribution pole-top capacitor banks alone. This model estimates that the portion of the total losses that are effected by the installation of the ACCs (Autodaptive Capacitor Controls) is one percentage point of the total 8%. This is a very conservative estimate.
3. In this model, it is assumed that ACCs are already in use for many applications (in an effort to provide better power factor profiles) and has consistently addressed the power factor problem. It was estimated that they have already saved approximately 75% of the available savings or ¾ of the total losses. Recouping the remaining ¼ of the total losses would be the additional savings attributed to the further change-out of equipment implementing the Volt/VAr Management System.

Given these basic assumptions, four categories of savings were looked at: 1) reduced losses, 2) reduced maintenance, 3) deferred capital expenditures, and 4) reduced operating costs.

Savings in Reduced Losses

Savings in Reduced Maintenance

In this model, there are approximately 400 LTC transformers installed and their maintenance interval is approximately 15 months based on the number of tap changer operations. Therefore,

Savings in Deferred Capital Expenditures

In this calculation, it is assumed that 5% of the upgrade or replacement of existing power transformers is the result of utilizing the Autodaptive® Volt/VAr Management System.

The assumption is made that additional generation will be required for the new load growth at 5% per year and that ¼ of the losses associated with the new generation would be saved as a result of utilizing the Autodaptive® Volt/VAr Management System. Therefore:

Savings in Operating Costs

In this model, it is estimated that the annual cost of engineering and field personnel time for capacitor bank control setting changes for seasonal and system changes is approximately $500 per control. Since the ACC needs no adjustments but rather adapts itself to seasonal and system changes, a subsequent operating cost reduction per unit would be realized after initial installation.

Investment Consideration

In this model, we considered investment in a new project to continue upgrades to the controls. Project cost considerations were broken out as follows:

Overall economic impact analysis and return on investment (ROI) study showed that if the new project were implemented, the annual savings of the new project, plus the other annual savings combined, would bear the following annualized saving results.

With annualized expected savings of $5,980,000 and new project costs of $2,520,000, utilities can receive a fast payback with a high ROI.

Of course, these calculations will vary from utility to utility depending upon their costs, their previous VAr management strategy, and their overall system configuration.

As is readily apparent, the majority of the overall savings (from all categories) is associated with the installation of the ACC control on the distribution pole top cap banks. It should be noted that the ACCs can be and are, without a doubt, "stand-alone" devices. The utilization of the full system, however, will maximize the Volt/VAr management results.

The first priority of any Volt/VAr Management System is to provide quality power at the customer's end. This quality is effected by both the method of voltage control on the tap changers and regulators, and by the VAr flow on the distribution system. The Autodaptive Volt/VAr Management System can quantify this measurement of power quality by monitoring and controlling the Voltage Regulation Quality Factor (VRQF).

The second priority is the control of the VAr flow through the distribution system as limited by the number of distribution line capacitors and substation bus capacitors available. This can be accomplished if the full implementation of the system is employed including the ATCs (Autodaptive Tapchanger Controls) and ARCs (Autodaptive Regulator Controls).

A third priority would be to accomplish the priorities mentioned above while reducing the total number of tap changes (LTC and Line Regulator) and thereby reduce the field maintenance associated with these devices. It should be noted that field testing of all these controls (ACC, ATC, and ARC) has shown a significant reduction in the number of tap changes as compared to the number of tap changes provided by conventional controls. Generally, 50% to 75% in the number of tap changes is typical.

Undoubtedly, the foundation for the Autodaptive® Volt/VAr System that controls distribution voltages and VAr flows, is the Autodaptive® Capacitor Control provided the feeder and/or substation has adequate compensation in the way of capacitance. Adding the Autodaptive tapchanger controllers (ATC and ARC) further completes the system and reduces the number of transformer and line regulator tap changes. All of this is done to improve and maintain a better Voltage Regulation Quality Factor (VRQF) and a desirable voltage profile and subsequent power factor that is delivered to the customer.

The individual components of the system have demonstrated their ability to work well as stand-alone devices, as well as working in conjunction with other supplier's equipment. They have demonstrated their ability to operate and coordinate with several other Autodaptive controllers on the same circuit or together on multiple circuits. The ATC however interacts only with the ACCs on the circuits and, as such, must be included in the complete Autodaptive Volt/VAr Management System in order to maximize the benefits.

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

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Hugo Davila has recently been appointed as Technical Support Engineer for Beckwith Electric. He comes to Beckwith from Lima, Peru, where he worked as a technical support engineer in the application, commissioning and marketing of protection and control apparatuses. His responsibilities at Beckwith include providing technical support to Latin American customers and representatives as well as the marketing of protection and control systems.

Prior to joining Beckwith, Hugo worked with Ferchale & Associates as a technical support/field engineer and as a local representative for Beckwith Electric. Hugo has also worked as a junior engineer for the electrical transmission company, Etecen, S.A. in the area of specialized maintenance. He has also been employed by Edelnor, S.A.-one of the main electric power utilities in Lima. At Edelnor, he worked as a substation maintenance engineer responsible for the application, commissioning and maintenance of electromechanical relays as well as the retrofit for digital relays.

Hugo has a degree in Electromechanical Engineering from the Engineering University of Lima, Peru. He graduated at the top of his class and received a Dean's award in his specialty for being the most outstanding Peruvian student from the 1995 class. Hugo is fluent in both Spanish and English.

Tony Brown, Latin American Regional Manager, expressed that Hugo's background in relay application and commissioning as well as his experience working with the utilities industry in Lima will be a tremendous asset to Beckwith Electric. Tony feels that the addition of Hugo to the Sales Department shows the commitment of Beckwith to the Latin American market. Hugo comments, "I enjoy working for Beckwith Electric because of its friendly employees, and I very much agree with Beckwith's philosophy of 'Honesty and Quality.' Working with relays is like a hobby to me, and I encourage customers to contact me with questions. I enjoy answering them."

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

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Literature Available

Capabilities Brochure
This brochure provides an overview of Beckwith Electric's product lines and outlines the company's capabilities in meeting customers' needs.

Technical Paper: "Coordinated Adaptive Distribution Volt/VAr Controls" (English and Spanish available)
This technical paper, presented at the Mexico IEEE's 1998 Summer Power Meeting (RVP), was authored by three Beckwith Electric employees: E. Tom Jauch, Manager Applications Engineering for Controls and Control Systems, Dr. Murty V.V.S. Yalla, VP of Research and Development/Engineering; and Andrew P. Craig, Senior Design Engineer II and Control Design Team Leader. This paper presents the philosophy and field results of Beta tests of an adaptive system for controlling distribution voltages and VAr flows. This system includes adaptive pole-top capacitor bank controls (ACCs), an adaptive transformer LTC voltage control (ATC) and an adaptive line regulator control (ARC).

Technical Paper: "Adaptive Control for Pole-Top Capacitor Banks"
This technical paper, presented at the 1997 Canadian Conference on Electrical and Computer Engineering, was authored by Dr. Murty V.V.S. Yalla, Beckwith Electric's VP of Research and Development/Engineering and E. Tom Jauch, Manager Applications Engineering for Controls and Control Systems. This paper investigates the timely operation of switched pole-top capacitor banks on distribution circuits and compares an innovative approach of capacitor-bank switching to those used by many conventional controls now in operation.

Technical Paper: "Design and Implementation of a Digital Volts per Hertz Protective Relay for Generators and Transformers"
This technical paper, authored by Dr. Murty V.V.S. Yalla, Beckwith Electric's VP of Research and Development/Engineering, was included in the transactions for the CIGRE Study Committee 34 Colloquium in Johannesburg, South Africa in 1997. This paper presents the design and implementation of a digital Volts per Hertz (V/Hz) protective relay for synchronous generators and power transformers. The paper proposes a new algorithm for the calculation of V/Hz. The algorithm is designed to work over a wide frequency range.

Technical Paper: "Digital Transformer Protection from Power Plants to Distribution Substations"(English and Spanish available)
This technical paper, presented at the Canadian Electricity Association's Electricity '98 Conference in Toronto, was authored by Chuck Mozina, Manager Applications Engineering for Protection and Protection Systems. This paper discusses how multifunction digital relays can improve protection of transformers at power plants and industrial plants, on transmission systems and at distribution substations-increasing security against false operations, as well as providing necessary protection.

Technical Paper: "Upgrading the Protection of Industrial-Sized Generators Using Digital Technology"
This technical paper, presented at the 1996 Industrial Applications Society Conference, for the Medium-Voltage Protection Subcommittee, was authored by Chuck Mozina, Manager Applications Engineering for Protection and Protection Systems. The paper presents the reasons why industrial generator owners should consider upgrading the electrical protection of their generators to meet today's standards. It outlines the risks assumed in five functional areas where 20+ year old generator protection is inadequate and discusses an upgrade program.

Technical Paper: "Protection of Independent Power Producer Generators Using Digital Technology" (English and Spanish versions available)<br> This article, authored by Chuck Mozina, was presented at the Canadian Electricity Forum in November 1997. This technical paper discusses the electrical protection of IPP generators and the specific protection requirements to interconnect these generators to utility systems. It also outlines the advantage of digital relay technology to provide this protection.

Article Reprint: "Protecting Generator Sets Using Digital Technology"
This article, authored by Chuck Mozina, was part of the EGSA supplement as reprinted from the November 1997 issue of Consulting/Specifying Engineer Magazine. This color, 4-page article reprint discusses how protective relaying technology guards generators not only from short circuits, but also from overexcitation, overvoltage and other abnormal operating conditions. It also highlights the benefits of "pick and choose" software functions for the protection of smaller generators (3 MVA or smaller).

The Capabilities Brochure and technical papers listed above can be downloaded from the Beckwith Electric website located at the Document Center on www.beckwithelectric.com.

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Articles from Issue 31, June 2000 of Beckwith Electric's Powerlines.
Copyright 2000.  All rights reserved. Reproduction of the whole or any part of the contents without written permission is prohibited.

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