h a v e a life e x p e c t a n c y a t a ho t t es t spo t t e m p e r a t u r e of 180 C c o m p a r a b l e t o t h a t of Glass A sys tems a t 105 G. S ince t h e A I E E S t a n d a r d N u m b e r 1 def in i t ion of Class H does n o t e x c l u d e t h e use of e n a m e l e d m a g n e t w i re , t h e sil icone sys tem qualif ies as Class H as def ined in this s t a n d a r d .

CONCLUSION

T h e t h e r m a l life va lues o b t a i n e d on t h e insu la t ion system b y t h r e e test m e t h o d s show exce l len t co r re l a ­t ion . D a t a h a v e b e e n p r e s e n t e d to show t h a t t h e modi f ied-sil icone e n a m e l e d wi re t o g e t h e r w i t h s i l icone c o m p o n e n t s p r o v i d e a n insu la t ion sys tem in r a n d o m - w o u n d elect r ic m a c h i n e s qual i fy ing for o p e r a t i o n a t Class H t e m p e r a ­tures .

REFERENCES 1. Test Procedure for Trial Use for the Evaluation of the Thermal Stability of Enam­eled Magnet Wire, AIEE Standard No. 57, AIEE Subcommittee on Dielectrics, October 1955.

2. A Method for Evaluation of Thermal Stability for Magnet Wire Enamel, C G. Currin, J . F. Dexter. AIEE Publication £-67, June 1954, pp. 19-26.

3. Thermal Endurance of Silicone Magnet Wire Evaluated by Motor Test, W. J. Bush, J . F. Dexter. AIEE Publications S-67, June 1954, pp. 67-72.

4. Statistical Methods (book), G. W. Snedecor. Iowa State College Press, Ames, Iowa, 1946, pp. 31-74, pp. 103-37.

5. Electrical Insulation Deterioration Treated as a Chemical Rate Phenomenon, T. W. Dakin. AIEE Transactions, vol. 67, 1948, pp. 113-22.

6. Heat-Resistant Insulation Systems for Motors, C. J . Herman, Κ. N. Mathei . AIEE Communication and Electronics, November 1955, pp. 561-5.

7. Motor Insulation Life as Measured by Accelerated Test and Dielectric Fatigue, C. J. Herman. AIEE Transactions, vol. 72, pt. I l l , 1953, pp. 986-91.

8. A Method of Evaluating Insulation Systems in Motors, C. B. Leape, J. McDonald, G. P. Gibson. AIEE Transactions, vol. 72, pt. I l l , 1953, pp. 793-99.

9. Aging of Small Motor Insulation, Κ. N. Mathes. AIEE Transactions, vol. 71, pt. I l l , 1952, pp. 254-62.

Pump-Turbine Addition at TVA Hiwassee Hydro Plant

L . R . S E L L E R S J . Ε . Κ I R K L A Ν D , J R . M E M B E R A I E E

Studies i n p r e p a r a t i o n for t h e insta l lat ion of a s e c o n d u n i t at H i w a s s e e D a m s h o w e d that t h e 2 6 - p e r - c e n t a d d i t i o n a l in s ta l l ed cost of a p u m p -t u r b i n e - t y p e u n i t w a s jus t i f i ed b y e c o n o m i c a n d o p e r a t i n g a d v a n t a g e s . D e s i g n a n d o p e r a ­t ion character is t ics o f th is 8 0 , 0 0 0 - h p u n i t , as w e l l as t h e field test to b e g i v e n after init ia l

o p e r a t i o n , are d i s c u s s e d .

H I W A S S E E D A M , bu i l t b y t h e T e n n e s s e e V a l l e y A u t h o r i t y ( T V A ) , is l oca t ed in t h e sou thwes t c o r n e r of N o r t h C a r o l i n a on t h e H iwassee R i v e r , a

t r i b u t a r y of t h e T e n n e s s e e R i v e r . T h e t o t a l s t o r age v o l u m e p r o v i d e d b y this d a m is 438 ,000 acre-feet , of w h i c h 304,700 is useful con t ro l l ed s to rage . C o n s t r u c t i o n was s t a r t ed in J u l y 1936, a n d p o w e r g e n e r a t i o n b e g a n in M a y 1940.

O p e r a t i o n of t h e pro jec t , w h i c h is c o n d u c t e d on a m u l t i p u r p o s e basis, is i n t e g r a t e d w i t h t w o u p s t r e a m reser­voirs , C h a t u g e a n d No t t e ly , b o t h c o m p l e t e d in 1942, a n d also w i t h A p a l a c h i a D a m , loca t ed 9.8 miles d o w n s t r e a m . T h e l a t t e r pro jec t , c o m p l e t e d in 1943 , c r ea t e s a rese rvo i r e x t e n d i n g to H iwassee D a m .

T h e o r ig ina l ins ta l l a t ion a t H i w a s s e e consists of o n e 120-r p m F r a n c i s - t y p e t u r b i n e r a t e d 80 ,000 h p a t 190-foot h e a d a n d a g e n e r a t o r r a t e d 64 ,000 k v a , 60 cps , 0.9 p o w e r factor . Des ign provis ions w e r e m a d e for t h e ins ta l l a t ion of a d u p l i c a t e u n i t a t a l a t e r d a t e .

F ig . 1 shows a g e n e r a l v iew of t h e p o w e r h o u s e a n d d a m . A 275- ton g a n t r y c r a n e of t h e o u t d o o r t y p e is p r o v i d e d to h a n d l e t h e t u r b i n e a n d g e n e r a t o r p a r t s t h r o u g h roof h a t c h e s . T h e h a t c h cove r for U n i t / c a n b e seen be low t h e c r a n e . U n i t 2 is n o w b e i n g ins ta l led on t h e r iver side of U n i t / .

P U M P TURBINE RECOMMENDED

S T U D I E S W E R E B E G U N , in 1 9 5 1 , in p r e p a r a t i o n for t h e

ins ta l l a t ion of t h e second u n i t a t H iwassee . A t t h a t t i m e t h e d e v e l o p m e n t of t h e p u m p t u r b i n e h a d r e a c h e d such a s t age t h a t a u n i t of this t y p e co u l d b e cons ide red for this p ro jec t . T h e Hiwassee p l a n t is wel l su i t ed for a p u m p e d s t o r a g e d e v e l o p m e n t , b e c a u s e t h e l ake fo rmed b y A p a l a c h i a D a m backs u p to t h e H i w a s s e e p o w e r h o u s e a n d provides a p p r o x i m a t e l y 8,700 acre-feet of w a t e r for p u m p i n g . T h i s is e q u i v a l e n t t o a b o u t 27 h o u r s of p u m p i n g a t r a t e d p u m p c a p a c i t y .

A t h o r o u g h s t u d y of t h e benefi ts to b e de r ived from t h e ins ta l l a t ion of a p u m p - t u r b i n e u n i t as c o m p a r e d w i t h t h e a d d i t i o n of a c o n v e n t i o n a l t u r b i n e was m a d e b y t h e p l an ­n i n g b r a n c h of T V A , w i t h t h e resul t t h a t ins ta l l a t ion of a p u m p - t u r b i n e u n i t w a s r e c o m m e n d e d . T h i s s t u d y ind i -Revised text of paper 56-145, "Pump-Turbine Unit 2 Addition at TVA Hiwassee Hydro Plant," recommended by the AIEE Committee on Power Generation and approved by the AIEE Committee on Technical Operations for presentation at the AIEE Winter General Meeting, New York, Ν. Y., January 30-February 3, 1956. Scheduled for publication in AIEE Power Apparatus and Systems, 1956.

L. R. Sellers and J. E. Kirkland, Jr., are with Tennessee Valley Authority, Knoxville, Tenn. The authors wish to acknowledge the valuable assistance of R. R. Lewis of the Division of Design.

M A R C H 1956 Sellers, Kirkland—Pump-Turbine Addition 263

c a t e d t h a t a sat isfactory r e t u r n on t h e 26 -pe r - cen t a d d i t i o n a l ins ta l led cost of a p u m p t u r b i n e w o u l d b e rea l i zed b e c a u s e of t h e inc reased o n - p e a k e n e r g y a n d g e n e r a t i n g c a p a c i t y a v a i l a b l e . I n a d d i t i o n , i m p o r t a n t b u t i n t a n g i b l e benefi ts m a y b e rea l ized , such as inc reased flexibil i ty of system o p e r a t i o n a n d t h e m a i n t e n a n c e of h i g h e r h e a d s a t o t h e r p l a n t s . T h e u p w a r d t r e n d in c a p a c i t y c h a r g e s a n d possible g r e a t e r different ial b e t w e e n p e a k a n d off-peak e n e r g y costs w o u l d also e n h a n c e t h e a d v a n t a g e of a p u m p - t u r b i n e -t y p e ins ta l la t ion .

F ig . 2A shows t h e e x p e c t e d a d d i t i o n a l a v a i l a b l e c a p a c i t y for t h e pe r iod of h i g h system l o a d . T h e a d d i t i o n a l c a p a c ­i ty is a resul t of t h e h i g h e r h e a d m a n t a i n e d on b o t h u n i t s b y off-peak p u m p i n g . T y p i c a l week ly o p e r a t i o n d u r i n g this pe r iod is s h o w n b y F ig . 2B. A d d i t i o n a l i n f o r m a t i o n in r e g a r d to e x p e c t e d o p e r a t i o n is a v a i l a b l e . 1 ' 2

After cons ide r ab l e consu l t a t i on w i t h t h e p u m p - t u r b i n e m a n u f a c t u r e r , t h e Al l i s -Cha lmer s C o m p a n y , M i l w a u k e e , Wis . , i t w a s d e c i d e d t h a t t h e u n i t shou ld b e r a t e d 80 ,000 h p a t a 190-foot n e t h e a d a n d shou ld o p e r a t e a t a speed of 105.9 r p m . I t w o u l d r o t a t e c lockwise as a t u r b i n e . I t w a s also d e c i d e d t h a t for p u m p o p e r a t i o n t h e u n i t s h o u l d b e r a t e d 3,900 cub i c feet p e r second (cfs) a t 205-foot n e t h e a d a n d o p e r a t e a t a speed of 105.9 r p m . O p e r a t i o n as a p u m p w o u l d b e coun te rc lockwise .

D u r i n g t h e ear ly s tages of p l a n n i n g , severa l a l t e r n a t e p u m p - t u r b i n e un i t s w e r e cons ide red . I t was first t h o u g h t t h a t t h e l imi t ing factor w o u l d b e t h e la rges t size r u n n e r t h a t c o u l d b e s h i p p e d in o n e piece . S u c h a u n i t w o u l d h a v e b e e n r a t e d a p p r o x i m a t e l y 48 ,000 h p a t 190-foot n e t h e a d as a t u r b i n e a n d 2,500 cfs a t 205-foot n e t h e a d as a p u m p . T h i s size w o u l d h a v e b e e n i n a d e q u a t e for T V A ' s r e q u i r e ­m e n t s as a t u r b i n e ; therefore , it w a s d e c i d e d t o b u i l d t h e r u n n e r in sect ions a n d assemble it in t h e field. T h e r u n n e r b e i n g ins ta l led is m a d e in t h r e e sect ions a n d is b o l t e d t o ­ge the r .

A 2-speed u n i t , t h a t is, o n e w h i c h w o u l d o p e r a t e a t o n e speed w h e n g e n e r a t i n g a n d a different speed w h e n p u m p ­ing , was also cons ide red . T h e 2-speed t y p e h a s t h e a d ­v a n t a g e of b e t t e r efficiency, i n a s m u c h as m a x i m u m effi­c iency of t h e u n i t for t u r b i n e o p e r a t i o n occurs a t a l ower speed t h a n for p u m p i n g . H o w e v e r , t h e g e n e r a t o r m a n u ­fac tu re r s consu l t ed d id n o t cons ide r it adv i sab l e t o des ign a p o l e - c h a n g i n g 2-speed s y n c h r o n o u s - t y p e u n i t of this size.

Fig. 1. Hiwassee project, 1940, Unit 1 installed

Cost , c r a n e lift, a n d s p a c e r e q u i r e m e n t s also w o u l d h a v e b e e n p r o h i b i t i v e for this ins ta l l a t ion .

T h e u n i t finally se lected w a s t h e largest , physica l ly , t h a t c o u l d b e ins ta l led in t h e s p a c e ava i l ab l e , a n d t h e speed se lected was a c o m p r o m i s e b e t w e e n best speed for p u m p i n g a n d bes t speed for g e n e r a t i n g .

T a b l e I lists r a t i ngs a n d o t h e r p e r t i n e n t d a t a for U n i t 7 t u r b i n e a n d g e n e r a t o r a n d , also, for t h e U n i t 2 p u m p t u r b i n e a n d g e n e r a t o r m o t o r .

DESCRIPTION OF PUMP TURBINE

T H E H I W A S S E E PUMP-TURBINE UNIT is s imi la r in a p p e a r ­

a n c e t o a c o n v e n t i o n a l F r a n c i s - t y p e t u r b i n e . T h e e m ­b e d d e d p a r t s consist of p la te-s tee l d r a f t - t u b e l iner , p l a t e -steel d i s c h a r g e r ing , cast-s teel s t ay r ing , p la te-s tee l sp i ra l case , a n d pla te -s tee l p i t l iner , as s h o w n in F ig . 3 . T h e sp i ra l case is of w e l d e d c o n s t r u c t i o n a n d is w e l d e d t o t h e s tay r ing , as s h o w n in F ig . 4 . T h e shop welds w e r e fu rnace a n n e a l e d . T o m i n i m i z e t h e a m o u n t of field w e l d i n g r e q u i r e d , t h e s tay r i n g a n d sp i ra l case sect ions w e r e m a d e as l a r g e as cons is ten t w i t h ease of h a n d l i n g a n d s h i p p i n g . T h e field welds w e r e stress-rel ieved b y t h e l o w - t e m p e r a t u r e f l ame stress-rel ieving process , a n d t h e c o m p l e t e d s tay r i n g a n d sp i ra l case w e r e hyd ros t a t i c a l l y tes ted a t a p ressu re of 1.5 t imes t h e des ign p ressure .

F l o w of w a t e r to t h e i m p e l l e r r u n n e r is con t ro l l ed b y 20 cast-s teel wicke t ga tes . T h e wicke t ga tes a r e c o n n e c t e d b y su i t ab l e levers a n d links to t h e shifting r i n g w h i c h is, in t u r n , c o n n e c t e d t o t h e 2 -ga te s e rvomoto r s . T h e servo­m o t o r s , a c t i n g u n d e r oil p ressu re f rom t h e governor , c o n t r o l t h e w i c k e t - g a t e o p e n i n g .

T h e i m p e l l e r r u n n e r is t h e p a r t t h a t mos t d is t inguishes t h e p u m p t u r b i n e f rom t h e c o n v e n t i o n a l F r a n c i s t y p e . F ig . 5 shows t h e r u n n e r in t h e e rec t ion a r e a after t h e t h r e e sect ions w e r e b o l t e d t o g e t h e r . T h e r u n n e r for t h e H iwassee u n i t h a s six v a n e s c o m p a r e d w i t h 19 in t h e c o n v e n t i o n a l u n i t , a n d its d i a m e t e r a t t h e c e n t e r l ine of t h e d i s t r i b u t o r is c o n s i d e r a b l y l a rge r . I t is set 6 feet l o w e r w i t h respec t to t a i l w a t e r t h a n t h e c o n v e n t i o n a l r u n n e r . T h e l a rge r d i a m e t e r a n d lower se t t ing a r e d i c t a t e d b y t h e p u m p i n g r e q u i r e m e n t s of t h e u n i t .

A n u m b e r of accessories, o r d i n a r i l y n o t p r o v i d e d for a c o n v e n t i o n a l t u r b i n e r e q u i r e d for t h e p u m p t u r b i n e a r e :

1. D r a f t - t u b e t r a s h r a c k s a r e p r o v i d e d to p r e v e n t t r a s h f rom e n t e r i n g t h e i m p e l l e r r u n n e r d u r i n g p u m p i n g o p e r a ­t ion . I t is i m p o r t a n t t h a t these t r a s h r a c k s d o n o t b e c o m e c logged a n d lower t h e effective t a i l w a t e r level sufficient t o cause c a v i t a t i o n in t h e impe l l e r r u n n e r . T o p r e v e n t o p e r a t i o n of t h e u n i t as a p u m p u n d e r these cond i t ions , a n a d d i t i o n a l t a i l w a t e r level i n d i c a t o r ha s b e e n p r o v i d e d ins ide t h e t r a sh racks . T h i s g a u g e is e q u i p p e d w i t h electr ic c o n t a c t s for a l a r m a n d s h u t d o w n in case t h e effective t a i l w a t e r level b e c o m e s too low.

2. E q u a l i z i n g p ipes a r e c o n n e c t e d b e t w e e n t h e h e a d cover a n d t h e draf t t u b e t o d e c r e a s e t h e p ressu re u n d e r t h e h e a d cover . T h i s r e d u c t i o n in p re s su re h a s t h e effect of r e d u c i n g t h e h y d r a u l i c t h r u s t a n d r e d u c i n g t h e disk fr ict ion.

3 . T w o i n d i c a t i n g f lowmeters a r e p r o v i d e d for U n i t 2— o n e for t u r b i n e o p e r a t i o n a n d o n e for p u m p o p e r a t i o n .

2 6 4 Sellers, Kirkland—Pump-Turbine Addition E L E C T R I C A L E N G I N E E R I N G

T h e s e a r e c o n n e c t e d to t h e s t a t i on flowmeter w h i c h r eco rds a n d to ta l izes t h e n e t p l a n t d i s c h a r g e . T h e n e t d i s c h a r g e is t h e to t a l d r a w n b y b o t h un i t s f rom t h e H i w a s s e e Rese rvo i r , m i n u s t h e a m o u n t r e t u r n e d t o t h e rese rvo i r b y p u m p i n g o p e r a t i o n on U n i t 2.

4. W i c k e t - g a t e b r a k e s a r e p r o v i d e d to p r e v e n t c h a t t e r ­ing or v i b r a t i o n of t h e wicke t ga tes , s ince m o d e l tests a n d o p e r a t i n g e x p e r i e n c e on s imi la r un i t s h a v e i n d i c a t e d t h a t c h a t t e r i n g m i g h t o c c u r a t c e r t a i n g a t e o p e n i n g s . T h e b rakes a r e a i r - o p e r a t e d a n d a c t d i r ec t ly on t h e g a t e s tems . T h e y a r e a u t o m a t i c a l l y c o n t r o l l e d so t h a t t h e b r a k i n g pressure is r e d u c e d w h e n t h e ga tes a r e m o v i n g in e i the r d i r ec t ion a n d a p p l i e d a t full p r e s su re w h e n t h e y a r e s t a t ion­a ry . T h e b r a k e s a r e n o t used w h e n t h e u n i t is o p e r a t i n g as a t u r b i n e .

5. T h e usua l facilities a r e p r o v i d e d for b l o w i n g t h e w a t e r d o w n be low t h e r u n n e r t o r e d u c e t h e p o w e r r e ­q u i r e d for o p e r a t i o n of t h e u n i t as a s y n c h r o n o u s c o n d e n s e r . A n o t h e r use for t h e b low r down facilities wil l b e t o r e d u c e t h e t o r q u e r e q u i r e d w h e n s t a r t i n g as a p u m p . B l o w d o w n m a y also b e useful for g r a d u a l l y r e d u c i n g t h e p o w e r i n p u t t o be low t h e i n p u t r e q u i r e d a t c losed g a t e , w h e n s h u t t i n g t h e u n i t d o w n from p u m p i n g o p e r a t i o n .

Model Tests. D u r i n g t h e des ign of t h e p u m p t u r b i n e , t h e m a n u f a c t u r e r m a d e a n u m b e r of tests on a n 18 - inch h o m o l o g o u s m o d e l to s u p p l e m e n t o t h e r des ign w o r k a n d to d e m o n s t r a t e t h a t t h e p u m p t u r b i n e will h a v e t h e des i red charac te r i s t i c s . Tes t s of t h e f inal m o d e l i m p e l l e r r u n n e r w e r e wi tnessed b y T V A p e r s o n n e l .

F r o m these tests its w a s d e t e r m i n e d , u s ing a c o n s e r v a t i v e efficiency " s t e p - u p " fac tor , t h a t t h e u n i t wil l m e e t t h e m a n u f a c t u r e r ' s efficiency g u a r a n t e e s for b o t h p u m p a n d t u r b i n e o p e r a t i o n . T h e tests also i n d i c a t e d t h a t t h e p u m p c a p a c i t y g u a r a n t e e s wil l b e m e t a t a l l h e a d s a n d t h a t t h e t u r b i n e c a p a c i t y g u a r a n t e e s will b e e x c e e d e d b e l o w 200-foot n e t h e a d , b u t will n o t m e e t t h e g u a r a n t e e a t 220-foot n e t h e a d b y a b o u t 2 ,000 h p . H o w e v e r , s ince t h e g e n e r a t o r c a p a c i t y l imi ts t h e p o w e r o u t p u t a t h e a d s a b o v e 200 feet, i t is obv ious t h a t i nc reased t u r b i n e o u t p u t a t t h e h i g h e r h e a d s w o u l d b e of l i t t le v a l u e ; therefore , n o a t t e m p t w a s m a d e to effect s u c h a n inc rease .

Tes t s w e r e also m a d e t o d e t e r m i n e t h e c a v i t a t i o n c h a r a c ­teristics of t h e u n i t , b o t h as a t u r b i n e a n d as a p u m p . T h e s e tests i n d i c a t e d t h a t for t u r b i n e o p e r a t i o n , c a v i t a t i o n w o u l d n o t o c c u r u n d e r a n y n o r m a l c o n d i t i o n . F o r p u m p ­ing o p e r a t i o n , t h e tests i n d i c a t e d t h a t t h e l imi ts i m p o s e d b y t h e m a n u f a c t u r e r , in t h e c o n t r a c t , w e r e sat isfactory. I t was also d e t e r m i n e d t h a t t h e p u m p c o u l d b e o p e r a t e d a t a s o m e w h a t l ower h e a d t h a n d i c t a t e d b y t h e c a v i t a t i o n l imi t b y t h r o t t l i n g t h e p u m p d i s c h a r g e w i t h t h e w icke t gates . H o w e v e r , b e c a u s e of d e c r e a s e d efficiency, th is low-h e a d o p e r a t i o n w o u l d n o t o r d i n a r i l y b e w o r t h w h i l e .

I n des ign ing t h e i m p e l l e r r u n n e r , it w a s necessa ry to g ive cons ide ra t i on to t h e p o w e r r e q u i r e m e n t s for p u m p o p e r a ­t ion , s ince t h e first m o d e l tes ted i n d i c a t e d t h a t t h e p o w e r r e q u i r e d b y t h e p u m p w o u l d exceed t h e m a x i m u m r a t i n g of t h e m o t o r b y a b o u t 4 p e r c e n t . T o l o w e r t h e p o w e r i n p u t to t h e m o t o r , t h e m a n u f a c t u r e r r e d u c e d t h e v a n e d i a m e t e r of t h e m o d e l ' s i m p e l l e r b y a n a m o u n t e q u a l to a b o u t 1 i n c h on t h e p r o t o t y p e . T h i s h a d t h e effect of

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Fig. 2. (top) Available plant capacity during period of high sys­tem load, (bottom) Typical weekly operation during period of high system load

r e d u c i n g t h e p u m p h o r s e p o w e r t o a n a c c e p t a b l e v a l u e a n d of r e d u c i n g t h e p u m p c a p a c i t y t o a p p r o x i m a t e l y 3,800 cfs a t a 205-foot n e t h e a d . T h e p u m p efficiency a n d t u r b i n e cha rac t e r i s t i c s w e r e subs t an t i a l l y u n c h a n g e d . Because of t h e i n a b i l i t y t o e x a c t l y p r e d i c t p r o t o t y p e p e r f o r m a n c e f rom a m o d e l test , i t w a s d e c i d e d to b u i l d t h e impe l l e r r u n n e r w i t h a d i a m e t e r of 266 inches a n d d o a n y necessary t r i m m i n g of t h e v a n e s in t h e field after c a p a c i t y tests a r e m a d e .

T o s u m m a r i z e , t h e m o d e l tests s h o w e d t h a t a p u m p t u r b i n e c o u l d b e bu i l t t o m e e t T V A ' s r e q u i r e m e n t s for a p u m p e d s t o r a g e u n i t for t h e H i w a s s e e p ro jec t . T h e exac t o p e r a t i n g cha rac t e r i s t i c s of t h e u n i t will b e d e t e r m i n e d b y field tests .

Operating Characteristics. F igs . 6 a n d 7 show t h e expec t ed p e r f o r m a n c e of t h e u n i t , o p e r a t i n g as a t u r b i n e a n d as a p u m p , respec t ive ly . T h e s e c u r v e s a r e based o n m o d e l test d a t a , g u a r a n t e e d g e n e r a t o r efficiencies, a n d ca l cu l a t ed pens tock losses. I t wil l b e n o t e d f rom F ig . 6 t h a t t h e m a x i m u m efficiency of t h e u n i t w h e n g e n e r a t i n g occurs a t m a x i m u m or n e a r l y m a x i m u m g a t e o p e n i n g a n d d r o p s off

M A R C H 1956 Sellers, Kirkland—Pump-Turbine Addition 265

Permanent Magnet Generator

Gate Operating Ring -

Wicket Gate Levers and Links -

Wicket Gate -

{El1312

- Generator Bus

efficiency p l o t t e d aga ins t p u m p dis­c h a r g e . T h i s c u r v e was c o m p u t e d f rom m o d e l test d a t a .

Runner Impeller 22'-2'D

Discharge Ring Draft Tube Liner

Fig. 3. Section through Unit 2, generator motor and pump turbine

r a t h e r r a p i d l y as t h e g a t e o p e n i n g is d e c r e a s e d . F o r this r ea ­son, t h e u n i t will n o t n o r m a l l y be o p e r a t e d a t p a r t l o a d n o r for l oad r e g u l a t i o n .

I t is i n t e res t ing t o n o t e t h a t t h e m a x i m u m r u n a w a y of t h e p u m p t u r b i n e is on ly a b o u t 42 p e r c e n t a b o v e r a t e d speed , wh i l e m a x i m u m r u n a w a y speed of t h e c o n v e n t i o n a l u n i t is a lmos t 100 p e r c e n t g r e a t e r t h a n r a t e d speed .

As s h o w n on F ig . 7, t h e over-a l l efficiency of t h e u n i t w h e n p u m p i n g is q u i t e h i g h over t h e e n t i r e o p e r a t i n g r a n g e . T h e excep t iona l ly flat c u r v e is p a r t i a l l y b e c a u s e of t h e m o v a b l e wicke t ga te s . F o r i n s t ance , if t h e u n i t w e r e o p e r a t e d a g a i n s t a 240-foot h e a d (2 ,900 cfs) a t t h e g a t e o p e n i n g r e c o m m e n d e d for a 190-foot h e a d (4,200 cfs), t h e efficiency a t t h e 240-foot h e a d w o u l d b e a b o u t 7 p e r c e n t poo re r t h a n t h a t s h o w n on t h e p e r f o r m a n c e c u r v e . T h e lower c u r v e of Fig . 7 shows t h e g a t e o p e n i n g for best

GENERATOR-MOTOR DESIGN

C O - O R D I N A T I O N of t h e g e n e r a t o r -

m o t o r des ign w i t h t h e p u m p t u r ­b i n e , m a i n t r ans fo rmer , a n d t r a n s ­miss ion- l ine charac te r i s t i c s invo lved a series of in te res t ing inves t iga t ions before t h e final des ign w a s se lec ted . T h e r e q u i r e d m o t o r o u t p u t of 102,-000 h p , or 76 ,092 kw, es tab l i shed a f r a m e size l a r g e r t h a n t h e g e n e r a t o r , r e q u i r e d t o m a t c h t h e t u r b i n e r a t e d o u t p u t of 80,000 h p . T h i s led t o t h e decis ion to r a t e t h e m o t o r a t 80 G rise. A u n i t y power - fac to r m o t o r , a l t h o u g h least expens ive , was found u n s u i t a b l e b e c a u s e of its lack of re­ac t ive c a p a c i t y t o con t ro l t r a n s ­miss ion- l ine a n d m a i n - t r a n s f o r m e r r e g u l a t i o n . A l t h o u g h a lower p o w e r fac tor w a s des i rab le , a c o m p r o m i s e figure of 0.95 was selected in o r d e r to l imi t t h e r o t o r w e i g h t to t h a t es­t ab l i shed by t h e c a p a b i l i t y of t h e exis t ing p o w e r h o u s e c r a n e . T h e m o t o r r a t i n g was t h u s es tab l i shed a t 102,000 h p , 0.95 p o w e r factor , 80 G

rise, 13,500 volts, a n d 105.9 r p m . T h e c o r r e s p o n d i n g g e n e r a t o r r a t i n g w a s specified as 59 ,500 /68 ,425 kw, 7 0 , 0 0 0 / 8 0 , 5 0 0 kva , 6 0 / 8 0 C rise, 0.85 p o w e r factor , a n d 105.9 r p m .

H i g h e r t h a n n o r m a l flywheel effect was n o t r e q u i r e d . T h e re la t ive ly h i g h ine r t i a c o n s t a n t of 3.71 s h o w n in T a b l e I for g e n e r a t o r p lus t u r b i n e was i n h e r e n t in t h e des ign .

T h e g e n e r a t o r m o t o r was furn ished by t h e Al l i s -Cha lmers M a n u f a c t u r i n g C o m p a n y . As s h o w n in F ig . 3 , it is enc losed in a c o n c r e t e b a r r e l c o n s t r u c t e d in tegra l ly w i t h t h e p o w e r h o u s e s t r u c t u r e , t h e s a m e as U n i t 7. A r e m o v ­a b l e f ab r i ca t ed steel cover p l aced j u s t a b o v e t h e p o w e r h o u s e d e c k level p rov ides c r a n e access for a s sembl ing a n d dis­m a n t l i n g t h e g e n e r a t o r m o t o r a n d p u m p t u r b i n e .

T h e d i rec t ly c o n n e c t e d m a i n a n d pi lo t exci ters a r e te le­scoped to r e d u c e h e a d r o o m r e q u i r e m e n t s . A n 84- inch-

Photo courtesy Allis-Chalmers Manufacturing Company

Fig. 4. Pump turbine, shop-assembled stay ring and spiral case Fig. 5. Unit 2, pump-turbine runner as assembled at site

2 6 6 Sellers, Kirkland—Pump Turbine Addition E L E C T R I C A L E N G I N E E R I N G

d i a m e t e r K i n g s b u r y t h r u s t b e a r i n g is l o c a t e d be low t h e ro to r , a n d e a c h of t h e 8 t h r u s t shoes a r e p r o v i d e d w i t h a h igh -p re s su re oil c o n n e c t i o n for r e d u c i n g t h e s t a r t i n g friction, A m o t o r - d r i v e n p u m p m o u n t e d e x t e r n a l l y o n t h e lower b e a r i n g b r a c k e t furnishes t h e h i g h - p r e s s u r e oil supp ly .

Six a i r coolers for t h e s t a t o r a r e m o u n t e d t a n g e n t i a l l y t o t h e s t a to r w r a p p e r p l a t e . A s h o p v iew w h i c h i l lus­t ra tes p a r t i a l l y s t acked r o t o r is s h o w n in F ig . 8. T h e n o r m a l p r a c t i c e of T V A is t o ins ta l l d i s c o n t i n u o u s - t y p e d a m p e r w i n d i n g s ; h o w e v e r , t h e c o n t i n u o u s t y p e , as s h o w n in F ig . 8, w e r e r e q u i r e d b y t h e p u m p s t a r t d u t y . N o t e t h e s t r a i g h t - t y p e fan b l a d e s m o u n t e d a b o v e t h e r o t o r . T h i s t y p e b l a d e is r e q u i r e d for revers ib le r o t a t i o n o p e r a t i o n .

V e n t i l a t i n g a i r s u p p l y for t h e exc i te rs is o b t a i n e d f rom t h e g e n e r a t o r r o o m a n d d i s c h a r g e d t h r o u g h ven t s in t h e g e n e r a t o r h a t c h cove r a b o v e t h e exci ters . P rov i s ion is m a d e to d i s c h a r g e this a i r b a c k i n t o t h e g e n e r a t o r r o o m w h e n r e q u i r e d t o r e d u c e s t a t ion h e a t i n g r e q u i r e m e n t s .

Motor Start Methods. V a r i o u s m e t h o d s cons ide r ed for s t a r t i ng as a m o t o r i n c l u d e d : (1) full vo l t age , n o r m a l f r equency ; (2) p a r t i a l w i n d i n g a t n o r m a l v o l t a g e a n d f r equency ; (3) s y n c h r o n o u s s t a r t f rom s tands t i l l b y m e a n s of 13.8-kv c o n n e c t i o n t o U n i t 7 ; (4) i n d u c t i o n s t a r t a t r e d u c e d vo l t age a n d f r e q u e n c y b y m e a n s of 13 .8-kv c o n ­nec t ion t o U n i t 7; a n d (5) r e d u c e d vo l t age , n o r m a l fre­q u e n c y , b y c o n n e c t i n g t h e m o t o r t o a 6 ,600-vol t t a p o n t h e m a i n t r a n s f o r m e r 13 ,200-vol t w i n d i n g .

M e t h o d 7 c o u l d n o t b e used b e c a u s e full v o l t a g e s t a r t w o u l d i m p o s e a 158 ,000-kva d e m a n d on t h e 161-kv sys tem. T h e g e n e r a t o r des igners d i d n o t r e c o m m e n d t h e use of p a r t i a l w i n d i n g s ta r t , m e t h o d 2, for th is t y p e m a c h i n e . M e t h o d s 3 a n d 4 w e r e p r a c ­t i cab l e b u t r e q u i r e d t h e use of U n i t 7 for e a c h d a i l y s t a r t h

d u r i n g t h e p u m p i n g season. ί M e t h o d 5 w a s a d o p t e d s ince Ε it w a s c a l c u l a t e d t h a t t h e m o t o r cou ld b e a c c e l e r a t e d to -n o r m a l speed in less t h a n 2 | m i n u t e s w i t h a s t a r t k i lovol t - t a m p e r e s of a b o u t 35 ,000 w i t h ; w a t e r depressed b e l o w t h e { p u m p r u n n e r . T h i s m e t h o d , 1

in a d d i t i o n to b e i n g en t i r e ly i n d e p e n d e n t of U n i t 7, h a d a f avorab le cost fac tor a n d w a s p a r t i c u l a r l y a d a p t a b l e t o a re la t ive ly s imp le c o n t r o l of al l p u m p - t u r b i n e a n d g e n e r a t o r -m o t o r o p e r a t i o n s f rom t h e m a i n c o n t r o l r o o m . T h e T V A system n o w has 42 hy ­d r o un i t s o p e r a t i n g w i t h th is t y p e of r e m o t e con t ro l , a n d has 6 superv i sory-con t ro l led un i t s in u n a t t e n d e d p l a n t s . 3

Table I. Comparison of Turbine and Pump-Turbine Units

Unit l , Turbine

Unit 2, Pump Turbine

Normal speed, rpm 120 Runner diameter at distributor center line, inches . . 161 Elevation

Distributor center line, feet 1,277 Bottom of draft tube, feet 1,240

Turbine characteristics Rated head, feet 190 Best efficiency head, feet 200 Rated output, hp 80 ,000 Runaway speed, rpm 235 Efficiency at rated head and hp 84 .7 Maximum efficiency 90 .0 Flywheel effect, pounds/square foot 2 ,600 ,000 Manufacturer Newport News

Pump characteristics Rated head, feet Rated discharge, cubic feet/second Efficiency at rated head and discharge, per cent.. Maximum efficiency

Generator characteristics Rated output (60 C), kva 64 ,000 Capability (80 C), kva 73 ,600 Power factor, per cent 90 Voltage 13,800 Efficiency at rated output and power factor, per

cent 97 .4 Flywheel effect, pounds/square foot 60 ,300 ,000 Thrust bearing total load, pounds 1,104,000 Manufacturer Westinghouse

Motor characteristics Rated output (80 C), hp Power factor, per cent Voltage Efficiency at rated output and power factor, per

cent Input kva at rated output and power factor

Generator plus turbine Inertia constant, kw second/kva. 3 .25 .

105.9 266

1,271 1,238.5

190 240

80,000 161

87 .3 89 .4

18,000,000 Allis-Chalmers

205 3 ,900

90 90

70,000 80,500

85 13,800

97.1 82,818,700

1,365,000 Allis-Chalmers

102,000 95

13,500

97 .4 82,250

3.71

4 0 50 60 70 G E N E R A T O R O U T P U T , M E G A W A T T S

Fig. 6. Unit 2 characteristics when generating

M A R C H 1956 Sellers, Kir Hand—Pump Turbine Addition 267

Ζ 30

tr g 20 ο 2 i n

2,400 2,800 3,200 3,600 4,000 D I S C H A R G E , C U B I C F E E T / S E C O N D

Fig. 7. Unit 2 characteristics when pumping

5,200

Generator-Motor p h a s e different ial

Protection. I n a d d i t i o n t o t h e spli t-o v e r c u r r e n t b a c k u p , a n d g r o u n d - f a u l t

re lays n o r m a l l y ins ta l led for t h e T V A h y d r o g e n e r a t o r s , t h e fol lowing p ro t ec t i ve devices w e r e p r o v i d e d :

1. T i m e r re lays for p r o t e c t i o n of r o t o r d a m p e r w i n d i n g s will t r i p t h e s ta r t b r e a k e r , if t h e m o t o r does n o t r e a c h 1-p e r - c e n t speed in a n o r m a l t i m e or if t h e m o t o r does n o t r e a c h s y n c h r o n o u s speed in a prese t t i m e . T h e s e re lays also p r o v i d e a t i m e d e l a y b e t w e e n s ta r t s t o a l low for coo l ing of s t a r t i ng w i n d i n g s .

2. A n u n d e r p o w e r r e l ay a n d a n out-of-s tep r e l a y will in i t i a te s h u t d o w n w h e n p u m p i n g t o p r o t e c t t h e m o t o r f rom t ransmiss ion- l ine d i s t u r b a n c e s .

3 . A field-failure r e l ay is p r o v i d e d .

I n a s m u c h as this m a c h i n e is g r o u n d e d t h r o u g h a resist­a n c e - l o a d e d d i s t r i b u t i o n t r ans fo rmer , s h u t d o w n f rom a g r o u n d faul t wil l b e in i t i a t ed b y a n e u t r a l v o l t a g e r e l ay .

OPERATION

R E F E R R I N G t o F ig . 9, it c a n b e n o t e d t h a t t h e g e n e r a t o r m o t o r , U n i t 2, is c o n n e c t e d to t h e m a i n t r a n s f o r m e r b a n k 2 t h r o u g h reve r s ing d i s connec t swi tches 213 a n d 215 a n d s ta r t a n d r u n b r e a k e r s 226 a n d 228. T h e s t a r t b r e a k e r connec t s t o a m i d - t a p of b a n k 2 l ow-vo l t age w i n d i n g s , g iving a n o m i n a l s t a r t v o l t a g e of 6,600 vol ts .

F o r a n o r m a l m o t o r s ta r t , t h e s w i t c h b o a r d o p e r a t o r first s ta r t s t h e u n i t auxi l ia r ies b y a m a s t e r c o n t r o l swi tch . T h i s o p e r a t i o n s tar t s t h e t h ru s t b e a r i n g oil p u m p , opens t h e s e a l - w a t e r a n d coo l ing -wa te r s u p p l y valves , a n d s tar t s t h e t u r b i n e - b e a r i n g oil p u m p . By p l a c i n g t h e o p e r a t i o n select ion swi tch in t h e p u m p pos i t ion , d i s connec t swi tch 213

is closed a n d t h e m o t o r -o p e r a t e d rheos t a t for t h e m a i n exc i te r field is r u n to a p r e ­selected pos i t ion .

Before t h e s ta r t b r e a k e r c a n b e closed, t h e fol lowing in te r ­locks m u s t i n d i c a t e t h a t c o n ­d i t ions a r e n o r m a l : (1) h e a d g a t e o p e n ; (2) p u m p swi tch (213) c losed ; (3) g o v e r n o r oil p ressure n o r m a l ; (4) a i r b r a k e s r e l eased ; (5) t h r u s t -b e a r i n g coo l ing -wa te r flow n o r m a l ; (6) tu rb ine - sea l w a t e r flow n o r m a l ; (7) t u r b i n e -b e a r i n g oil level n o r m a l ; (8) t h r u s t - b e a r i n g s t a r t i ng oil p re s su re n o r m a l ; (9) exc i te r field r h e o s t a t in t h e p r e ­selected " s t a r t " pos i t ion ; (10) t a i l w a t e r level ins ide draf t t u b e a b o v e t h e l imi t ing m i n i ­m u m e l eva t i on ; (11) w a t e r depressed be low t h e p u m p i m p e l l e r ; (12) field b r e a k e r o p e n ; a n d (13) p i lo t exc i t e r f ie ld-revers ing swi tch m u s t b e in p u m p posi t ion .

W h e n all in te r locks a r e in t h e pos i t ion r e q u i r e d for s t a r t i ng , as i n d i c a t e d b y a l a m p on t h e b e n c h b o a r d , t h e o p e r a t o r will close t h e s t a r t b r e a k e r , w h i c h in i t ia tes t h e fol lowing s e q u e n c e : (1 ) m o t o r will s t a r t a t r e d u c e d vo l t age ; a t a p p r o x i m a t e l y 95 -pe r - cen t speed , a po l a r i zed field f r equency r e l ay will close t h e field b r e a k e r a t t h e o p t i m u m r o t o r slip pos i t i on ; a n d (2) af ter a sho r t t i m e de l ay , t h e s ta r t b r e a k e r wil l t r i p a n d t h e r u n b r e a k e r will close t h r o u g h a s y n c h r o n i s m check r e l ay ; t h e o p e n t r ans i t i on t i m e will b e a p p r o x i m a t e l y 1 second , as r e q u i r e d for t h e m o t o r r o t o r to d r o p b a c k a p p r o x i m a t e l y 60 e lec t r ica l degrees , w h i c h is t h e p h a s e dif ference b e t w e e n t h e m a i n t r a n s f o r m e r s t a r t a n d r u n d e l t a c o n n e c t i o n s .

A d v a n c i n g t h e g a t e l imi t se t t ing will t h e n o p e n t h e a i r bleed-off va lve , p r i m e t h e p u m p , a n d b u i l d u p t h e m o t o r p o w e r i n p u t t o t h a t r e q u i r e d b y t h e p u m p a t shutoff h e a d , o r a p p r o x i m a t e l y 27 ,000 k w . A float swi t ch c o n n e c t e d t o t h e t u r b i n e o u t e r h e a d cove r will i n d i c a t e w h e n t h e p u m p is p r i m e d , after w h i c h t h e wicke t ga tes c a n b e o p e n e d to t h e pos i t ion for best efficiency a t t h e exis t ing o p e r a t i n g h e a d , as s h o w n on c u r v e in F ig . 6.

N o r m a l s h u t d o w n will i nvo lve closing t h e wicke t ga tes a n d a d m i t t i n g a i r t o depress t h e t a i l w a t e r be low t h e impe l l e r . O p e r a t i o n c a n t h e n b e c o n t i n u e d as a c o n d e n s e r ; o r if c o m p l e t e s h u t d o w n is r e q u i r e d , t h e o p e r a t o r will t r i p r u n b r e a k e r 228, w h i c h s ta r t s t h e t h r u s t - b e a r i n g oil p res ­su re p u m p a n d app l ies t h e b r a k e s of t h e g e n e r a t o r m o t o r w h e n t h e u n i t ha s d e c e l e r a t e d t o 50 -pe r - cen t speed .

FIELD TESTS

Pump-Turbine Tests. T h e T V A p l a n s to m a k e c o m p l e t e efficiency a n d c a p a c i t y tests of t h e p u m p t u r b i n e for b o t h

268 Sellers, Kirkland—Pump Turbine Addition E L E C T R I C A L ENGINEERING

p u m p a n d t u r b i n e o p e r a t i o n as soon as p r a c t i c a l after ini t ia l o p e r a t i o n . T h e Al l en sa l t -ve loc i ty m e t h o d w a s chosen for d e t e r m i n i n g t h e flow t h r o u g h t h e u n i t b e c a u s e it is r ead i ly a d a p t a b l e to e i t he r p u m p or t u r b i n e o p e r a t i o n . T h e p r inc ip l e of th is m e t h o d is t o in ject a q u a n t i t y of sal t solut ion i n t o t h e pens tock a n d m e a s u r e e lec t r ica l ly t h e t i m e r e q u i r e d for t h e so lu t ion t o t r a v e l a k n o w n d i s t a n c e b e t w e e n t w o po in t s in t h e pens tock . T h i s t r a v e l t i m e is used for c o m p u t i n g t h e a v e r a g e w a t e r ve loc i ty .

I t is t en ta t ive ly p l a n n e d to m a k e p u m p tests a t b o t h highl­a n d low- t a i lwa te r e leva t ions a n d a t sufficient different g a t e posi t ions to d e t e r m i n e t h e g a t e o p e n i n g t h a t gives best efficiency for t h e cond i t i ons exis t ing a t t h e t i m e of e a c h test. T u r b i n e tests will cove r t h e e n t i r e r a n g e of g a t e open ings , so t h a t a c o m p l e t e c h a r a c t e r i s t i c c u r v e for t h e h e a d exis t ing a t t h e t i m e of t h e test wil l b e o b t a i n e d .

D a t a o b t a i n e d f rom these tests will b e used to revise t h e o p e r a t i n g cha rac t e r i s t i c curves , t o c a l i b r a t e t h e p u m p a n d t u r b i n e f lowmeters , a n d to check t h e m a n u f a c t u r e r ' s efficiency a n d c a p a c i t y g u a r a n t e e s .

Generator-Motor Tests. A c o m p l e t e set of s eg rega t ed loss tests b y t h e dece l e r a t i on m e t h o d will b e m a d e after c o m ­ple t ion of t h e in i t ia l o p e r a t i o n tests. S u p p l e m e n t a l tests w i t h osci l lographs will also b e m a d e to d e t e r m i n e s t a r t i n g a n d pul l - in cha rac te r i s t i c s for m o t o r o p e r a t i o n .

CONCLUSIONS

T H E FOLLOWING CONCLUSIONS necessar i ly a p p l y on ly for t h e h y d r a u l i c a n d o p e r a t i n g c o n d i t i o n s a t t h e H iwassee h y d r o p l a n t :

1 . T h e 26 -pe r - cen t a d d i t i o n a l ins ta l led cost of a p u m p -t u r b i n e - t y p e u n i t a t H iwassee w a s just i f ied b y t h e e c o n o m i c a n d o p e r a t i n g a d v a n t a g e s t h a t will b e o b t a i n e d as c o m p a r e d to a c o n v e n t i o n a l - t y p e u n i t .

2 . As d e m o n s t r a t e d b y m o d e l tests, a p u m p t u r b i n e w i t h good efficiency for b o t h p u m p a n d t u r b i n e o p e r a t i o n a t a c o m m o n speed c a n b e bu i l t . T h e efficiency as a t u r b i n e d r o p s off r a t h e r r a p i d l y as t h e g a t e o p e n i n g is d e ­c r e a s e d ; howeve r , t h e u n i t will n o t b e n o r m a l l y o p e r a t e d a t p a r t l oad .

3 . G e n e r a t o r - m o t o r f r a m e size a n d cost w e r e es tab l i shed b y t h e m o t o r r e q u i r e m e n t s .

4. O f t h e several m o t o r s t a r t i n g m e t h o d s inves t iga ted , a r e d u c e d vo l t age s t a r t u t i l i z ing a m a i n t r a n s f o r m e r m i d -

LINE LINE

161 KV BUS 2

h V 161 KV BUS I

Transformer bank I ,61-13.2 kv j Α Λ γ Λ Λ —

cooled, 75,000 161-13.2 kv J Starting tap

Station service

transformer

f480 volts

Generator I S ^ \ 64,000kva, 60cps \ 73,600 kva, 80cps \ U N I T 1J 13.8 kv, 3ph, 60cps y y 120 rpm 1 * 1

2,3<i Motor connected

hp 215 ^Generator I connected

Generator 2 70,000 kva, 60cpsf 80,500 kva, 80cps\ UNIT 2 I I3.8kv,3ph,60cps\ 105.9 rpm Motor 102,000 hp,jBOcps c = > ^ :

13.5 kv, 105.9 rpm

Fig. 9. Connection diagram, Units 1 and 2

t a p w a s f o u n d a d v a n t a g e o u s f rom t h e o p e r a t i o n , con t ro l , a n d cos t v i ewpo in t s .

5 . W a t e r shou ld b e depres sed b e l o w t h e r u n n e r d u r i n g t h e s t a r t cyc le s ince 36 p e r c e n t of ful l - load t o r q u e is r e ­q u i r e d a t t h e p u m p shutoff h e a d .

6. S e m i a u t o m a t i c c o n t r o l of t h e p u m p t u r b i n e a n d g e n e r a t o r m o t o r s t a r t i n g a n d o p e r a t i o n w a s found p r a c ­t i cab l e w i t h r e m o t e superv i s ion f rom t h e m a i n c o n t r o l r o o m .

REFERENCES 1. Record-Size Pump-Turbine To Be Installed at TVA's Hiwassee Project, Reed A. Elliott, Don H. Mattern. Civil Engineering, New York, Ν. Y., March 1953, pp. 56-9.

2. Pump-Turbine Unit at Hiwassee Aids TVA, Harry Wiersema. Electrical World, New York, Ν. Y., May 11, 1953.

3. Supervisory Control and Remote Control Help T V A Cut Operating Costs, R. M. Alspaugh, A. P. Maness, AIEE Transactions, vol. 73, pt. III-B, 1954, pp. 863-69.

4. Pump-Turbines 1954 Progress Report, Frank E. Jaski. Allis-Chalmers Electrical Review, Milwaukee, Wis., Fourth Quarter 1954, pp. 16-18, 24-6.

5. Generator-Motor Units for Reversible Pump-Turbines, H. H. Roth. Ibid., pp. 20-3.

6. Flatiron Power and Pumping Plant, John Parmakian. Mechanical Engineering, New York, Ν. Y., August 1955, pp. 677-80.

7. Pumped Storage and Hydro Generation at Flatiron Power Plant, S. M. Denton, H. O. Britt. AIEE Power Apparatus and Systems, vol. 74, August 1955, pp. 614-18.

Fig. 8. Unit 2, 70,000-kva/102,000-hp generator-motor shop view of partially stacked rotor with poles fitted

Photoengraving Process

A p h o t o e n g r a v i n g p l a t e - m a k i n g process , m a n y t h o u s a n d s of t imes faster t h a n c o n v e n t i o n a l m e t h o d s , ha s b e e n d e ­v e l o p e d b y R a d i o C o r p o r a t i o n of A m e r i c a . E m p l o y i n g t h e " E l e c t r o f a x " sys tem of e lec t ros ta t ic p h o t o g r a p h y , a c o m p l e t e l i t h o g r a p h i c p l a t e c a n b e m a d e in less t h a n a m i n u t e , a n d a p r i n t i n g p l a t e c a n b e p r e p a r e d for e t c h i n g in a few m i n u t e s . T h e process involves c o a t i n g m e t a l o r o t h e r surfaces w i t h i nexpens ive p i g m e n t for d i rec t ex­p o s u r e . T h i s process m a y b e a p p l i e d to p r i n t e d circui ts .

M A R C H 1 9 5 6 Sellers, Kirkland—Pump Turbine Addition 269