FLATIRON POWERPLANT AUTOMATIC VOLTAGE

REGULATOR PERFORMANCE

October 1989

U.S. DEPARTMENT OF THE INTERIOR Bureau of Reclamation

Denver Office Research and laboratory Services Division

Electric Power Branch

Bureau ot Reclamation

FLATIRON POWERPLANT AUTOMATIC VOLTAGE REGULATOR PERFORMANCE ,

October 1989 6. PERFORMING ORGANIZATION CODE

!

7. AUTHOR(S)

J. C. Agee

9. PERFORMING ORGANIZAT ION NAME A N D ADDRESS

Bureau of Reclamation Denver Office Denver CO 80225

- -- * - -- _ - I - - Same

14. SPONSORING AGENCY CODE

D-3772

8. PERFORMING O R G A N l Z A T l O N REPORT NO.

R-89-16 10. WORK U N I T NO.

11. CONTRACT OR GRANT NO.

12. SPONSORING AGENCY NAME AND ADDRESS

I DlBR 15. S U P P L E M E N T A R Y NOTES

13. T Y P E O F REPORT AND PERIOD COVERED

1 Microfiche and hard copy available at the Denver Office. Denver, Colorado. I . 16. ABSTRACT

Tests on the uprated unit 1 at Flatiron Powerplant were conducted during December 1988. Excitation system performance tests conducted at that time are described. -

17. K E Y WORDS A N D DOCUMENT ANALYSIS

a. DESCRIPTORS-- voltage regulators/ control equipment/ electric power production/ excitation/ power system stability/

b. ID E ~ T I F IE RS-- voltage regulators/ Flatiron Powerplant/ Eastern Colorado Projects Office/

c . COSATl Field/Group COWRR: SR IM:

18. D lSTR lBUT iON STATEMENT 19. SECURITY C L A S S (THIS REPORTf _ UNCLASSIFIED .

20. SECURITY CLASS (THIS PAGE)

UNCLASSIFIED

El. NO. CtF PA-S

. 47 -

22. P R I C E ",

FLATIRON POWERPLANT AUTOMATIC VOLTAGE

REGULATOR PERFORMANCE

by

J. C. Agee

Electric Power Branch Research and Laboratory Services Division

Denver Office Denver, Colorado

October 1989

UNITED STATES DEPARTMENT OF THE INTERIOR + BUREAU OF RECLAMATION

ACKNOWLEDGMENTS

Special thanks to Mr. Hoa Vu who participated in the tests and alsoprepared appendix D on model representation.

Mission: As the Nation's principal conservation agency, theDepartment of the Interior has responsibility for most of ournationally owned public lands and natural and culturalresources. This includes fostering wise use of our land andwater resources, protecting our fish and wildlife, preservingthe environmental and cultural values of our national parksand historical places, and providing for the enjoyment of lifethrough outdoor recreation. The Department assesses ourenergy and mineral resources and works to assure that theirdevelopment is in the best interests of all our people. TheDepartment also promotes the goals of the Take Pride inAmerica campaign by encouraging stewardship and citizenresponsibility for the public lands and promoting citizenparticipation in their care. The Department also has a majorresponsibility for American Indian reservation communitiesand for people who live in Island Territories underU.S. Administration.

The information contained in this report regarding commercialproducts or firms may not be used for advertising or promotionalpurposes and is not to be construed as an endorsement of anyproduct or firm by the Bureau of Reclamation.

The research covered by this report was funded under the Bureauof Reclamation PRESS (Program Related Engineering andScientific Studies) allocation No. DR-496, Power System StabilityEnhancement.

11

CONTENTS

Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Regulator adjustment philosophy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Ratings and calibrations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Off-lineperformance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

On-line performance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Automatic limiters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Relaycoordination. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Startup performance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Load rejection performance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Pump start performance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

TABLES

Table

123

Machineoperating points. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .URAL limiter data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Load rejection performance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

FIGURES

Figure

123456789

Generator saturation cUlVe""""""""""""""""""

Exciter saturation cUlVe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Small signal step response of off-line a-c regulator. . . . . . . . . . . . . . . . . . .Frequency response of off-line a-c regulator. . . . . . . . . . . . . . . . . . . . . . . .Off-line step response of d-c regulator. . . . . . . . . . . . . . . . . . . . . . . . . . . .Small signal step response of on-line a-c regulator. . . . . . . . . . . . . . . . . . .Frequency response of on-line a-c regulator. . . . . . . . . . . . . . . . . . . . . . . .Local mode damping response. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Capability cUlVe

""""""""""""""""""""""

III

Page

1

1

1

2

3

3

3

5

5

6

6

246

789

101112131415

Figure

101112

13a13b14a14b1516

Appendix

AB

,CD

CONTENTS - Continued

Overexcitation limiting coordination. . . . . . . . . . . . . . . . . . . . . . . . . . . . .Terminal voltage limiter operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Normal startup performance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Rated load rejection via lockout relay, recorder No.1. . . . . . . . . . . . . . . .Rated load rejection via lockout relay, recorder No.2. . . . . . . . . . . . . . . .Rated load rejection via unit breaker operation, recorder No.1. . . . . . . . .Rated load rejection via unit breaker operation, recorder No.2. . . . . . . . .Pump start failure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Successful pump start. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

APPENDIXES

Special conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Test connections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Parameter record. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Computer model representation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

IV

Page

161718192021222324

25293337

INTRODUCTION

Flatiron Powerplant houses two medium-size hydroelectric generators and a single pump generator.The two generating units were electrically up rated in 1985. In addition, the original Rototrolvoltage regulators were replaced with new automatic voltage regulating equipment consisting ofoperational amplifier-type voltage regulating and limiting circuits, control relaying, and a thyristor-type power amplifier. The original rotating main exciters were retained.

Uprated turbine runners were not installed at that time; therefore, the units had never operatedat their full uprated megavolt-ampere capability until the November 1988 installation of the firstnew runner on unit 1. Due to uncertainties concerning the rated field current of the machine atfull load, the excitation system was never set for proper operation at full load. Thus, when unit 1was ready to return to service at the uprated value, tests were required to set the excitation systemlimits properly for the up rated conditions.

J. C. Agee and Hoa Vu (Controls and Automation Section) participated with Bruce McCarthy(Eastern Colorado Projects Office) in the excitation system tests. Concurrent with these tests, BillDuncan (Engineering Division, Facilities Engineering Branch), John German (Eastern ColoradoProjects Office), and LeRoy Heigel and Tom Hovland (Electrical and Mechanical EngineeringDivision, Mechanical Branch, Hydraulic Machinery Section) conducted tests on the governor andturbine of the unit.

CONCLUSIONS

The excitation system was successfully adjusted for operation at the new uprated value.Coordination between the maximum excitation limiter and the exciter overvoltage relays is marginaland needs to be addressed further by means of a detailed technical study. This problem is beingaddressed on a Reclamation-wide basis. When a generator lockout occurs, phase back of theregulator should be initiated prior to opening of the field breaker. This is necessary to reduce theovervoltage experienced during load rejections. Project personnel are revising control circuits toinclude this function.

REGULATOR ADJUSTMENT PHILOSOPHY

Because the rating of the Flatiron machines is under 50 MV.A (megavolt amperes), power systemstabilizers were not purchased. Therefore, the automatic voltage regulators could decrease thelocal-mode stability margin if they were adjusted for maximum speed of response. For this reason,the regulators were tuned for moderate speed and a high level of damping. Since the Flatiron unittransformers have a low impedance, the voltage regulators are set with a droop characteristic whichlocates the regulation point approximately 5 percent inside the machine terminals. This limits themachines' reactions to high-side voltage fluctuations while still providing needed voltage supportat the B.8-kilovolt bus for starting the unit 3 pump generator.

RATINGS AND CALIBRATIONS

The Flatiron generators are rated at 47.8 MV.A and 0.9 power factor. Rated voltage is13.8 kilovolts and rated current is 2,000 amperes. Full megavolt-ampere output is obtained withreal power at 43 megawatts and reactive power at 20.8 megavars.

The PT (potential transformer) ratio is 120:1 and the CT (current transformer) ratio is 2,000:5.The voltage regulator terminal voltage transducer (at terminal C of A5CB) produces 53.8 volts d.c.(direct current) at rated terminal voltage.

The base field current required to produce rated terminal voltage on the air gap line is 212 amperes(fig. 1). The field resistance at 25°C is 0.3607 ohm. At a typical operating temperature, theresistance increases to 0.42 ohm. Therefore, the base field voltage is 89 volts at normal operatingtemperatures. The field voltage transducer in the regulator (at terminal 4 of JVT) has a calibrationof -8 volts of output for 260 volts of input. This signal has a base of 2.74 volts per unit.

The rotating exciter base field current required to produce 89 volts from the exciter on its air gapline is 4.5 amperes (fig. 2). The exciter field resistance is 3.947 ohms at 75°C. At a typicaloperating temperature, the corrected resistance is 3.4 ohms. Therefore, the base exciter fieldvoltage is 15.4 volts at normal operating temperatures.

Several machine quantities and excitation levels for various conditions are shown in table 1.

Table 1. - Machine operating points

Megawatts MegavarsVt

(kilovolts)Ifd

(amperes)Efd

(volts)lex

(amperes)Eex

(volts)

04343

01 In18 Out

13.813.914.2

242357505

93146210

4.267.32

12.3

14.224.842.4

Vt = Terminal VoltageIfd = Main Field CurrentEfd = Main Field Voltagelex = Exciter Field CurrentEex = Exciter Field Voltage

At rated conditions (43 megawatts, 20.8 megavars), field current is approximately 510 amperes at220 volts with a winding temperature of 75°C. These values have been selected as rated valuesfor limiter and relay coordination.

2

OFF-LINE PERFORMANCE

The automatic voltage regulator was tuned by adjusting A4P to its minimum [CCW(counterclockwise)] position. The automatic regulator gain was set at 4.4, lead at 10.0, and lag at0.0. Figure 3 shows the small signal step response of the closed-loop automatic voltage regulatingsystem with the unit off line at rated voltage and speed. The 10- to 90-percent rise time is about0.4 second. The overshoot is 13 percent. Response is almost symmetrical for both increases anddecreases in terminal voltage. The control system performance is well damped with only oneovershoot and no apparent oscillations.

A Bode plot of the frequency response of the off-line automatic regulating system is shown infigure 4. The 3-decibel bandwidth is approximately 1.2 hertz, and the resonant peak magnitude isless than 1 decibel above the steady-state gain. These values indicate a moderate-speed, well-damped control system.

The range of the automatic regulator adjuster was not tested since the unit had been in service andperforming satisfactorily for several years.

The minimum setting of the 70P [d-c (direct-current) regulator adjuster] was not adjusted; however,its maximum setting was adjusted via the range pot to obtain field voltage of 230 volts (105 percentof rated). The d-c regulator response was tested by transferring from the a-c (alternating-current)regulator with an unbalance between their outputs. Figure 5 shows this response. Performance isadequate; however, it may be readjusted during the unit 2 tests in order to reduce overshoot andimprove damping.

ON-LINE PERFORMANCE

The automatic voltage regulator did not need to be retuned for on-line operation. Figure 6 showsthe small signal step response of the closed-loop automatic voltage regulating system with the uniton line at full load and unity power factor. The 10- to 90-percent rise time is about 1.6 seconds.There is no overshoot. The control system performance is well damped with no apparentoscillations. Figure 7 shows a Bode plot of the on-line automatic voltage regulating system. The3-decibel bandwidth is about 0.2 hertz. Local mode resonance appears well damped. Figure 8shows the damping of local mode when stimulated by a pulse in field voltage. The local modefrequency is near 2 hertz. The oscillations are totally damped in three to four cycles, whichindicates a damping factor of about 0.2.

AUTOMATIC LIMITERS

The Flatiron regulators are equipped with V1Hz (volts per hertz) URAL (underreactive amperelimiters) and maximum excitation limiters. These limiters supervise only the a-c regulator and takecontrol if certain conditions occur. They do not function if the regulator is in d-c (manual)regulator mode.

3

The V 1Hz limiter was not tested because the unit had been in satisfactory commercial service.However, upon investigation in Denver, no record of tests on this device could be found in theoriginal test report. Therefore, this device will be tested during the unit 2 tests.

The URAL prevents the generator from operating too far underexcited. Table 2 lists severalpoints at which the URAL becomes active. These points are shown on the capability curve infigure 9.

Table 2. - URALlimiter data.

Megawatts Megavars

1019304448

171n171n13 In81n1 In

The maximum excitation limiter has two functions: (1) it provides a fixed instantaneous exciterfield current limit, allowing a high level (typically 150 percent) of excitation for a short time; and(2) it provides an inverse time characteristic after which the excitation limit is recalibrated andreduced to the rated value.

The primary limit on exciter field current is set to 16.8 amperes via the AlP dial setting of 4.8.This corresponds to about 275 volts from the rotating exciter during startup (exciter unloaded).When the exciter is at rated load, 260 volts are induced from this current. With a hot generatorfield (75°C), this will produce 605 amperes of main field current (120 percent of full-load, ratedpower factor). With a cold field (25 °C), it will produce 725 amperes (142 percent) of main fieldcurrent.

After 8 to 10 seconds (inverse-time characteristic), circuit board J2CB should operate relay J1 K andreduce the exciter field current limit to 11.5 amperes. This will reduce the rotating exciter outputto about 220 volts. This results in 511 amperes (100 percent) of main field current with a hot fieldand 610 amperes (120 percent) with a cold field. During startup when the exciter is unloaded, thisvalue of exciter field current produces 221 volts.

During testing of the recalibrated limiter, the llP potentiometer was found to have an open circuitat a dial setting of 7.5. The pot was therefore rewired with the opposite sense. The final settingwas 4.0 on the dial.

If the maximum excitation limiter does not work properly and the rotating exciter output remainsabove 235 volts for 36 seconds (inverse-time characteristic), circuit board llCB will operate relayJ2K and transfer to the manual regulator at the autotracked position. For this contingency, themaximum position of the manual regulator was set to only slightly above the rated value.

4

RELAY COORDINATION

If the rotating exciter output remains above 255 volts for 40 seconds, relay 59E will operate throughtimer J2KX/TD and thereby trip the lockout relay.

If the rotating exciter output reaches 300 volts, relay 59E/H will operate and trip the lockout relay.These coordination levels are shown on figure 10.

Relay 159 is the primary terminal voltage limiter. If terminal voltage remains above 110 percentfor 3 seconds, this relay will pick up through timer 159X and transfer the regulator to a fixed phase-back circuit. This circuit is set to fully phase back the regulator bridge. When terminal voltagedrops below 110 percent, the relay drops out and returns bridge control to the automatic or manualregulator that was in service before the overvoltage condition. During testing of this device, itwas discovered that proper operation could not be obtained if the phase-back signal was less than-3 volts; therefore, it was set to -2.5 volts. Operation of terminal voltage limiting is shown onfigure 11.

If terminal voltage remains above 115 percent (or if the V/Hz ratio exceeds 115 percent) for5 seconds, relay 159 V /Hz will pick up and trip the generator lockout relay.

If terminal voltage remains above 115 percent for 8 to 10 seconds (inverse-time characteristic), orif it ever exceeds 140 percent, relay 159 I/T will pick up and trip the generator lockout relay.

STARTUP PERFORMANCE

The Flatiron generators are not equipped with a 90-percent speed switch, so a timer is employedto close the field breaker after the low-speed switch detects rotation. When first tested, this timerwas set too fast resulting in the field breaker closing at 67 percent speed. This condition wascorrected.

The voltage regulators are powered by station service rather than from the machine terminals;therefore, field flashing is not employed. Because of this situation, the a-c regulator will not buildvoltage unless there is sufficient residual to activate the V/Hz limiter circuitry. Enough residualwas detected during our tests; however, for consistent automated performance, the regulators wereset up to start in d-c regulator mode and then transfer to a-c regulator mode after the field breakeris closed.

Figure 12 shows a normal automatic start of unit 1. Transfer from the d-c to the a-c regulator isapparent. Voltage buildup is accomplished in about 5 seconds with very little overshoot in terminalvoltage. The 59E relay was observed to pick up, but its time delay J2KX/TD blocked further action(proper operation). Relay 59E/H did not pick up.

5

10 megawatts, 0 megavars 104 101 102

30 megawatts, 0 megavars 123 100 109

44 megawatts, 17 megavars out 139 102.5 136field breaker

44 megawatts, 17 megavars out 140 102.5 128phase back

LOAD REJECTION PERFORMANCE

Load rejections were executed at 10-, 30-, and 44-megawatt levels. Two rejections were initiatedat 44 megawatts in order to compare performance of voltage regulator phase-back operation to fieldbreaker opening with discharge resistor insertion. Results are summarized in table 3.

Table 3. - Load rejection performance.

Load Overspeed(percent)

Prerejectionvoltage

(percent)Overvoltage

(percent)

Figure 13 shows a rated load rejection executed by tripping the lockout relay (86G). This actioncaused the field breaker to trip immediately without regulator phase back. Figure 14 shows a ratedload rejection executed by opening the unit breaker. The lockout relay was tripped later, after thevoltage had recovered to its prerejection level. Project personnel will revise the control circuitryto provide regulator phase-back operation prior to field breaker opening when the lockout istripped. This will limit the overvoltage on rated load rejections by an additional 8 percent.

PUMP START PERFORMANCE

An important function of the voltage regulators at Flatiron is to support system voltage during astart of the unit 3 pump motor. Prior to proper adjustment of the overexcitation limiters, operationof the main units was limited to half load while the pump was starting. Operation at higher loadsduring this time would cause either a pump synchronizing failure because of an excessive voltagedrop, or the generator tripping on overexcitation, or both.

The initial setting of the overexcitation limiter resulted in a starting failure because the 59E relaywas set too low. This is documented in figure 15. The field voltage was 247 volts (112 percent)when the machine tripped. Proper operation was obtained by readjusting the 59E to 255 volts(116 percent) and the overexcitation limiter time delay to a lower value. Figure 16 shows asuccessful pump start. Operation of the overexcitation limiter is apparent. The 59E relay wasobserved to check that it did not pick up.

6

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8

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11

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14

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24

APPENDIX A

Special Conditions

25

The phase-back circuit did not function properly unless the voltage was greater than -3 volts. Thecircuit was set to -2.5 volts to provide a safety margin.

The overexcitation limiter recalibration potentiometer (JIP) had an open circuit at a dial positionof about 7.5. Its connections had to be reversed to obtain proper operation.

During the pump start, the inverse timer board for J lK acted erratically. This should be checkedduring the unit 2 tests.

The cams for the d-c regulator need to be reset sinc~ the range was adjusted. Project personnelwere planning to do this.

27

APPENDIX B

Test Connections

29

The test set frequency and voltage transducers were connected to the PT disconnect knife switchin the relay cubicle.

Exciter field current was measured at the shunt in the field breaker cubicle. Exciter field voltagewas measured both at terminals in this cubicle and directly across the exciter field aI the fieldbreaker terminals for certain tests.

Main field voltage was measured at the GE (General Electric) transducer in the regulator cubicle.

The input signal to the regulator was applied at the spare input (power system stabilizer signa]input) on the regulator motherboard connector.

31

APPENDIX C

Parameter Record

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APPENDIX D

Flatiron Computer Model Representation(by Hoa Vu)

37

The off-line model of Flatiron unit 1 was studied. The block diagram of the model is presentedin figure D-1. The generator is modeled with a gain of 0.51 p.u. (per unit) and. a pole at3.6 seconds. The exciter has a gain of 5.1 V/V (volt/volt), and a pole at 1.33 seconds. The baseof Efd is 92 V/p.u. If the exciter gain is changed from 5.1 V/V to 1 p.u., then the base for Vbr is18 V/p.u. The bridge gain is 37 VIV; the regulator is 5 VIV; and the base of Vt is 54.15 V/p.u.The gains of bridge and regulator are combined and then converted to a per unit value of 550.

The rate feedback is modeled with a zero at d.c., gain of 0.02 p.u., and a pole of 0.675 second. Theinput of rate feedback circuit is from Efd transducer (ratio of 260/8). Therefore, the base at theinput of rate feedback circuit is 2.83 V/p.u. The output of rate feedback is not truly connected atthe reference input summer. There is a gain of 2.5 V/V from the output of the reference summerto the point where the output of rate feedback is connected. If the connection of the rate feedbackis modeled at the reference summer, then there is a factor of 1/2.5 in the gain of rate feedback.

This model gives responses that match field data very well (see figs. D-2 through D-7), but thereare two problems:

1. The rate feedback gain of 0.02 p.u. is converted to 0.3827 VIV. Then, take a factor of1/2.5 out to have the gain of the circuit itself of 0.957 VIV. The rate feedback circuit hasthe gain of the feedback resistor [20 k (k ohm)] times the input capacitor. Therefore, thecapacitor should be 47.8 microfarads. The real circuit configuration shows it should be100 microfarads because of two 50-microfarads connected parallel. Therefore, maybe onecapacitor is failed or open.

2. The rate feedback time constant of 0.675 second is calculated as the combination of two100-k resistors paralleled with 100-k pot (min), added with 4.75 k and then multiplied withthe input capacitor (50 microfarads). If the factor of the capacitor is taken out of 0.675second, then the total resistance should be 13.5 k. If 4.75 k is subtracted from the totalresistance, then there is 8.75 k left for the pot (min) paralleled with two 100 k. If the potis at minimum, then its resistance paralleled with two 100 k should be zero. Therefore, theminimum of the pot may have 10 k ohms.

These problems can be reconciled by measuring the transfer function of the rate feedback circuitdirectly. This will be accomplished during the tests of unit 2.

39

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Figure 0-7. - Model frequency response with A1P at 4.0.

176.32

Mission of the Bureau of Reclamation

The Bureau of Reclamation of the U.S. Department of the Interior is responsible for the development and conservation of the Nation's water resources in the Western United States.

The Bureau's original purpose "to provide for the reclamation of arid and semiarid lands in the West" today covers a wide range of interrelated functions. These include providing municipal and industrial watersupplies; hydroelectric power generation; irrigation water for agriculture; water quality improvement; flood control; river navigation; river regulation and control; fish and wildlife enhancement; outdoor recreation; and research on water-related design, construction, materials, atmospheric management, and wind and solar power.

Bureau programs most frequently are the result of close cooperation with the U.S. Congress, other Federal agencies, States, local governments, academic institutions, water-user organizations, and other concerned groups.

A free pamphlet k available from the Bureau entitled "Publications for Sale.' It describes some of the technical pubiications currently available, their cost, and how to order them. The pamphtet can be obtained upon request from the Bureau of Reclamation, Attn D-7923A, PO Box 25007, Denver Federal Center, Denver CO 80225-0007.