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Issue 26 - March 1999
Since its introduction in 1995, the Autodaptive® Capacitor Control (ACC) has proven to be a success; nevertheless, the product has gained additional features—all in direct response to customer’s needs and requests. Now designated as model M-2501A, the ACC and its associated products have been enhanced by some of the following improvements:
According to Drew Craig, Beckwith Electric’s Manager of Research and Development--Controls, these additional features have made the ACC even easier to use without compromising the basic platform of the control that has proven to be so successful.
Beckwith Electric is proud to announce the Autodaptive® Volt/VAr Management System—a system of products that utilizes the coordinated operation of independent, adaptive, distributed, intelligent devices on the distribution system. This system consists of autodaptive pole-top capacitor bank controls (ACC’s), autodaptive tapchanger controls (ATC’s), and autodaptive regulator controls (ARC’s). See the Typical Autodaptive System figure. The system uses voltage regulation quality factor (VRQF), defined as the rms deviation of the voltage from a reference voltage as recursively averaged over a moving six hours, as a control target and a proposed standard method of stating the quality of voltage regulation. The benefits provided by this system over traditional methods or SCADA control of VAr and voltage controls are numerous. These benefits include:
The features of the Autodaptive Volt/Var Management System that provide these benefits include:
There are two features that are being proposed for the future. The first
feature will be transformer load management which provides an input to
the ATC for transformer oil temperature. The control will have the ability
to reduce the bus voltage to reduce peak loads if the internal transformer
temperatures approach damaging levels. The second feature will be control
of substation capacitor banks. System Components M-2501A Autodaptive Capacitor Control (ACC) The ACC’s on any distribution circuit work together, without communications, using very precise measurement of the fundamental component of voltageand comparison to previous voltage profiles, to help regulate the voltage furnished to customers along the line. By compensating for VArs required in the vicinity of each capacitor bank, the power factor along the distribution feeder remains near unity.
Local interface with the ACC is completed by "blinking" its infrared port or by using switches that are accessible when the Lexan cover is removed. Blinking is accomplished from under the ACC using either an HP200LX palmtop computer with its infrared port or an M-2920A BecoEye® Infrared Communications Adapter with a laptop computer. A 10-foot range is obtainable with the BecoEye. Blink data includes a history of the last 16 switch operations, the resulting voltages and the time of switching as well as a 24-hour voltage profile and VRQF. Much of the LTC transformer or regulator output voltage variation is reduced by downstream ACC operations. The necessary tapswitch operations per week are greatly reduced from those necessary with conventional controls. The operation of the ACC, when used on distribution feeders, is based on the measured voltage at the bank location as well as the history of voltage and switch operations. The autodaptive algorithms use three adaptations to determine the controls operation:
Since its introduction, several thousand ACC’s have been ordered with many individual orders from utilities calling for over one hundred controls apiece. The largest single order to date was for one thousand units to a major investor-owned utility company in the Midwest. M-2667 Autodaptive Tapchanger LTC Control (ATC) and M-2670 Series of Autodaptive Regulator Controls (ARC) The system location and programming of the ATC allow it to monitor the distribution system VAr requirements and calculate internal transformer VAr requirements. This allows the control to target unity power factor at the primary side of the transformer. The ATC precisely measures the fundamental component of distribution substation output voltage and uses this in comparison to previous measurements to determine how to influence the ACC’s switching patterns to modify VAr flow. The ATC and ARC incorporate several important advancements that distinguish them from the conventional voltage control. These innovative new controls operate in conjunction with the ACC's on the radial distribution feeders to control both voltage and reactive power flow in the distribution system as described earlier. First, unlike traditional controls, both the ATC and ARC use measured transformer or regulator VAr flow to temporarily adjust the voltage bandcenter to influence the ACC's to more rapidly add or remove capacitor banks on the feeders. Second, unlike traditional controls, the ATC and ARC include operations that are based on the Voltage Regulation Quality Factor (VRQF). Traditional controls operate using a voltage level setting, a fixed bandwidth and a fixed time delay (see the Control Comparison figure). The ATC has a voltage level setting, a bandwidth (one or two volts) as determined by the intertap voltage of the transformer and a VRQF setting. The resulting band edges are where adaptive non-linear integrating timers begin their operation. The Control Comparison figure illustrates the increased sensitivity of the Autodaptive controls versus conventional controls. The combination of the three controls form the Beckwith Electric hands-off, no communications required (NCR) distribution watt, VAr, and voltage quality control system. System Priorities The first priority of the Autodaptive Volt/Var Management System is to maintain the quality of the customer’s power as established by the control of VRQF. The second priority is the VAr flow through the distribution source as limited by the number of distribution line capacitors or substation bus capacitors available. Field testing has shown a significant reduction in tap changes compared to conventional controls to maintain equivalent VRQF values on the bus. Interested? For more information, contact Beckwith Electric at (727) 544-2326 or e-mail at marketing@beckwithelectric.com.
Autodaptive© Capacitor Control Gains Wide Acceptance In the fall of 1995, Beckwith Electric introduced the M-2501 Autodaptive Capacitor Control (ACC) for pole-top distribution line capacitor banks. Since then ACC's have been purchased by over 55 companies. The ACC introduced a new concept in capacitor controls—an adaptive capability that permits the control to adapt to changing system and circuit conditions. According to Tom Jauch, Beckwith Electric’s Manager of Application Engineering for Controls and Control Systems, this adaptability means that the ACC not only requires less knowledge from the operator regarding system parameters but performs its functions more accurately because it "learns" about the voltage profile of the system on which it is located. See "A New Autodaptive® Volt/Var Management System". Scott Lee, Applications Engineer for Central Power & Light (CP&L) of Texas, would agree. Lee is in charge of the North Central Division of CP&L’s distribution operations. One of his responsibilities in this capacity is to test new products and report the results of his findings to other engineers within the company. In 1997, CP&L purchased ten ACC’s and installed them on a two-bank substation with six distribution feeders. According to Lee, "the purpose was to see if the control would really work as the manufacturer promised it would." After allowing the controls to work for a year, Lee checked the results. The No.1 LTC transformer averaged 7.5 tap changes per day, down from 11.7 prior to the installation of the ACC’s, and the No. 2 LTC transformer averaged 7.1 tap changes per day, down from 14.6. This was despite extreme weather conditions such as drought, record high temperatures and floods. In addition to the reduced number of tap changes, Lee reported in an article from The PQ Monitor—a newsletter published by CP&L’s Technical Service Group that "station voltage charts showed smoother curves, but about the same high and low values. The incremental changes in voltage were less, showing that the ACC’s were doing a better job of regulating the distribution voltage. The station bank kVAr charts also looked much smoother… ." Because the ACC’s settings change or "adapts" to the operating environment, Lee compared the ACC to an autofocus camera—"why worry about settings and adjustments when the machine will do them for you?" The reduction of time and effort in determining and implementing settings and special conditions of the distribution circuits is the reason for one midwestern utility’s purchase of several hundred ACC’s. The utility has stated that the annual savings with this feature pays for the controls. Interested? For more information, contact Beckwith Electric at (727) 544-2326 or e-mail at marketing@beckwithelectric.com.
In 1969, Beckwith Electric began producing the M-0067, an analog tapchanger control that became known for its reliable performance as a solid state voltage relay using R.M.S. averaging voltage measurement techniques. In 1993, the M-2001 tapchanger control was introduced, offering digital signal sampling and expanded control features including communications, reverse power operation, and "keep-track" tap position knowledge. Today, Beckwith Electric is proud to introduce the M-2667 Autodaptive® Tapchanger Control (ATC). The M-2667 Autodaptive® Tapchanger Control provides a unique microcontroller-based solution to load tapchanging transformer (LTC) control requirements. Using conventional LTC inputs, the M-2667 ATC is designed to provide improved regulation based not only on voltage sensing, but also on Watt and VAr profiles. The ATC has a customer settable bandcenter, bandwidth, and Voltage Regulation Quality Factor (VRQF) that allows optimization of the tapchanger process. The goal of the M-2667 ATC is to provide a comprehensive solution for optimizing tapchanger control for the specific installation and operating environment. To accomplish this, the control works hand-in-hand with the Autodaptive Capacitor Controls (ACC), that are designed for VAr optimization of switched pole-top capacitor banks using Voltage Measurements and past profiles for capacitor bank switching optimization.) The M-2667 looks at VAr requirements on the load feeders and using a "voltage biasing" algorithm, it influences the ACCs to switch on and off to further optimize power factor. Physically, the ATC is identical in form and fit to the M-0067E analog tapchanger control. The ATC has two rows of barrier terminal screw contacts at the bottom of the backside of the control as compared to a single row for the M-0067E. The bottom row of contacts duplicates the connection on the M-0067E with the exception of terminal two which has been changed from a voltmeter output screw to a separate return for the line CT. The upper row of contacts on the ATC accommodates the additional features such as alarms, counter inputs, etc. The adaptive nature of the ATC provides optimization of tapchange timing to minimize unnecessary operations while still maintaining tight voltage regulation. In addition, the use of VRQF is introduced which is the RMS deviation in voltage from the settable reference voltage. The major benefit of the application of the VRQF control algorithm, as compared to the conventional technique, is more precise voltage regulation with reduced tap operations. The reduction of tapchanger operations is amplified when ACCs are used on the distribution feeders. The adaptive techniques can also restrict tapchanges based on large current magnitudes. This extends contact life and reduces maintenance. The Human-Machine interface consists of LEDs to indicate raise/lower timing (3 stages) and CPU OK status. Communications are through a front panel mounted DE-9 connector using the Slim-Com® Communications Protocol in an RS-232 interface. Setting of operating points and downloading of history data, power outage data and current status data are accomplished using Slim-Com software. Additional features include counter contact inputs, status inputs for "keep track" tap position functions, overcurrent tapchange inhibit and a multifunction alarm output. Interested? For more information, contact Beckwith Electric at (727) 544-2326 or e-mail at marketing@beckwithelectric.com.
Beckwith Electric’s LTC Backup control, now designated as model M-0329B, has been redesigned to include two significant improvements:
The M-0329B meets UL listing requirements for both the USA (UL 508, 16th edition) and Canadian standard C22.2 No. 14-M91. The M-0329B LTC Backup Control provides the extra protection that can help safeguard from the hazards and inconvenience of excessively high or low voltages on the distribution system. It does so by:
These functions are important in the event of a primary control failure or when heavy loads and line drop compensation combine to cause excessive voltages for customers close to the substation. It is often thought that because the M-2001 incorporates the same "first customer protection" setting parameters as the M-0329B, a backup is not needed. However, no device can be its own backup. If the M-2001 Tapchanger Control fails, it cannot back itself up. Therefore, Beckwith recommends the use of a backup control such as the M-0329B for the M-2001 or any tapchanger control. Interested? For more information, contact Beckwith Electric at (727) 544-2326 or e-mail at marketing@beckwithelectric.com.
In the summer of 1995, Beckwith Electric introduced their IPS (Integrated Protection System®) line with the M-3430 Generator Protection Relay for high-impedance generators and the M-3420 Generator Protection Relay for low-impedance generators. In the summer of 1998, the M-3310 Transformer Protection Relay was introduced. Beckwith Electric now has a new addition to the IPS family—the M-3520 Intertie Protection System. Like the other members of the IPS family, the M-3520 includes:
User-Selectable Functionality Interconnection protection requirements vary widely according to generator size, point of interconnection to the utility system, type of generator (induction, synchronous) and interconnection transformer configuration. These variables make user-selectable functionality an important feature; it allows the user, rather than the relay manufacturer, to specify the configuration of the relay. The M-3520 Intertie Protection System is offered as either a "protection system" with an array of functions that are usually necessary for more common applications, or as a "base system" with a core of functions to which optional functions can be added to accommodate specific applications. See the One-Line Diagram figure. This feature allows the M-3520 Intertie Protection System not only to meet a wide range of application needs but also to provide flexible packaging at the lowest possible cost. The M-3520 Intertie Protection System achieves the five main objectives (and incorporates the corresponding relay functions) inherent in any interconnection protection system; the objectives are as follows. Detection of Loss of Parallel Operation with the Utility System--The most universal means of detecting loss of parallel operation with the utility is to establish an over/underfrequency (81O/U) and over/undervoltage (27/59) "window" within which the IPP generator is allowed to operate. When the IPP generator is islanded from the utility system, either due to a fault or other abnormal condition, the frequency and voltage will quickly move outside the operating "window" if there is a major mismatch between load and IPP generator level. In some applications, the rate of change of frequency relays (81R) are used to more rapidly detect the loss of utility supply. When induction generators are islanded with pole-top capacitors and the generator capacity is near that of the islanded load, a resonant condition that produces a non-sinusoidal overvoltage can occur. For these cases, the M-3520’s instantaneous overvoltage (59I) function responds to peak overvoltage to detect this situation. Fault Backfeed Detection--The following M-3520’s functions are used to provide phase fault backfeed detection: phase directional overcurrent (67), phase distance (21) or inverse time overcurrent with voltage control or voltage restraint (51V). Ground fault backfeed removal depends on the primary winding connection of the interconnection transformer. Therefore, for grounded primary windings, a neutral overcurrent (51N) function or in some cases, the ground directional overcurrent (67N) function is used. For ungrounded interconnection transformers, neutral overvoltage (59N, 27N) functions provide the detection for supply ground faults. Detection of Damaging System Conditions--Protection against unbalanced currents is provided by the negative sequence overcurrent (46) function. To provide protection for phase reversals caused by inadvertant "phase swapping" after power restoration, a negative sequence voltage (47) function is also available. Abnormal Power Flow--The M-3520 has, as an option, a directional power (32) function for those utilities that need to trip the IPP if power inadvertently flows into the utility system for a predetermined time in violation of the interconnect contract. Restoration--A sophisticated sync-check function is provided which not only measures phase angle (D q ), but also slip frequency (D F) and voltage difference (D V) with dead line/bus control options. Communications Capability The M-3520 Intertie Protection System features allow integrated distributed control of digital protection with PLC systems. The M-3520 is equipped with serial communications ports (RS-232 and RS-485) to allow it to interface with PLCs. Metering and data (volts, amps, KW, KVAR, power factor and relay operating targets) within the relay can be accessed by a PLC through these communications ports. This saves the cost of wiring dedicated transducers for each metering quantity. Interested? For more information, contact Beckwith Electirc at (727) 544-2326 or e-mail at marketing@beckwithelectric.com.
Replacement Panels Save Time and Money Beckwith Electric has earned a reputation in the utility industry for easy tapchanger control replacements for both LTC transformers and regulators, beginning with the popular M-0067E which has been produced for over twenty-five years. This reliable, accurate control has been used not only as a direct replacement for the Westinghouse SVC and SVR controls, but as the basis for replacing numerous other controls. Each of these direct replacements was designed to allow the customer to disconnect the wiring from the existing control, remove it, mount the Beckwith replacement and reconnect the wiring. This made replacing or updating an old, outdated, or failed control as easy as possible. In 1993, the M-2001 Digital Tapchanger Control was introduced with a variety of adapter panels. The digital control offers communications capability along with other features and capabilities not available in analog controls. The adapter panels provide the mechanical and electrical configuration needed for easy direct replacement of most controls. Although Beckwith Electric offers a wide selection of direct tapchanger control replacements, sometimes the same model of a manufacturer’s control may have multiple versions or may have changed over time. These cases can be very frustrating to customers. To alleviate this problem, Beckwith Systems Engineering provides engineering services to "mark-up" or "red line" the customer’s drawings for a specific transformer or regulator. Typically, a schematic diagram and a wiring diagram are needed for the existing control. The wiring diagram shows a representation of the location of components and terminal blocks, a rear view of the control panel and any other panels such as the motor control panel, fan control panel, and so on. Ordinarily, the "red line" shows what to remove and where to connect the new control on both the schematic diagram and the wiring diagram. When a direct replacement is not available, Beckwith Systems Engineering can supply a complete, custom-designed panel specifically designed to replace the existing one. In most cases, a complete panel is needed when the existing control has failed or the present panel has multiple components such as: a balance beam type of voltage regulator, a separate time delay relay for raise and lower, a discrete switch for automatic/manual control, a discrete switch for manual raise and lower, discrete potentiometers for the line drop compensation settings, or separate circuit breakers for motor power and voltage. Using a custom designed replacement panel saves the customer considerable time for their engineers and field crews. For example, it may take several days of engineering time to complete the conversion design and provide instructions for the field crew. The field crew needs time for removal of all components and their associated wiring, plus time to modify the existing panel, mount the new control and wire the new control. The custom replacement panel is designed to minimize the time to change out the entire panel, sometimes taking as little as four hours. Terminal blocks are located in the same position, existing wiring connects in the same locations, and the mounting is designed to be the same as the old panel. The field crew only has to label and disconnect the wires that go from the enclosure to the existing panel, remove the panel, install the new panel using the same mounting holes or hinges and reconnect the wires to the new terminal blocks. A quick check is conducted to assure everything is working correctly and the crew is done. To accomplish this smooth conversion, Beckwith Electric needs the schematic diagram, the wiring diagram and detailed dimensions of the existing panel. This solution has been provided for many companies over the years. Upgrading or adding paralleling operations to LTC transformers using the circulating current method are situations where custom replacement panels also make sense. A custom replacement panel, containing a new control and the equipment needed for paralleling, is designed to minimize conversion time. A one-line diagram, schematic diagram, wiring diagram, and detailed dimensions of the existing panel are needed to evaluate if paralleling using the circulating current method can be applied. For converting from the master/slave method of paralleling to the circulating current method, a replacement panel is required. In addition to the items described above, the customer also needs to provide the drawings of the master/slave scheme to evaluate if there are enough connections between the transformers and where the signals for the new paralleling method can be connected. Interested? For more information, contact Beckwith Electric at (727) 544-2326 or e-mail at marketing@beckwithelectric.com.
Articles from Issue 26, March 1999 of Beckwith Electric's Powerlines. |
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