Kilovar Planning for Southern California Edison

J. H . D R A K E M E M B E R A I E E

G. A . D A V I S M E M B E R A I E E

EF F E C T I V E K I L O V A R P L A N N I N G , w h i c h is be ­c o m i n g c a p a c i t o r p l a n n i n g for m a n y e lec t r ica l

systems, r equ i r e s d e t a i l e d k n o w l e d g e of sys tem r e a c t i v e p o w e r charac te r i s t i c s a n d o p e r a t i n g r e q u i r e m e n t s . P l a n ­n i n g k i lovar g e n e r a t i n g c a p a c i t y t h e n b e c o m e s a n a l o g o u s to p l a n n i n g k i l o w a t t g e n e r a t i n g c a p a c i t y . I n b o t h in­s tances , l o a d is forecast a n d g e n e r a t i n g c a p a c i t y for t h e load p lus a p p r o p r i a t e r e se rve for sys tem con t ingenc i e s is p l a n n e d .

T h e r eac t i ve d e m a n d a n d s u p p l y for t h e S o u t h e r n Cal i forn ia E d i s o n C o m p a n y sys tem is s h o w n in F ig . 1. M a x i m u m over -a l l sys tem r e a c t i v e d e m a n d of 1.93 mi l l ion k v a r o c c u r r e d in J u l y 1954 a t w h i c h t i m e t h e r e a l p o w e r d e m a n d w a s 1.83 mi l l ion k i lowa t t s . C h a r g i n g k i lovars w e r e a b o u t e q u a l to t h e r e a c t i v e losses of t h e 1,900-mile, 220-kv sys tem. S y n c h r o n o u s c o n d e n s e r s s u p p l i e d 63 p e r c e n t of 1.43 mi l l ion k v a r of r e a c t i v e d e m a n d exis t ing a t t h e 66-ki lovol t level a n d be low, w h i l e s ta t ic c a p a c i t o r s supp l i ed 25 p e r c e n t . T h e r e a c t i v e g e n e r a t i n g m a r g i n for system con t ingenc ies w a s a v a i l a b l e in s y n c h r o n o u s con ­densers a n d i n s t e a m p l a n t s n e a r t h e l o a d c e n t e r .

F ixed c a p a c i t o r s o n 4-ki lovol t c i rcu i t s c o r r e c t e d c i rcu i t p o w e r fac tor t o u n i t y a t l igh t l oads . M o s t c a p a c i t o r s on h i g h e r v o l t a g e d i s t r i b u t i o n c i rcui t s w e r e swi t ched , e i the r seasonal ly o r b y v o l t a g e c o n t r o l . C a p a c i t o r s a t subs ta t ions w e r e u sua l l y swi t ched , e i t he r m a n u a l l y b y superv isory con t ro l , o r a u t o m a t i c a l l y w i t h c u r r e n t b i a sed vo l t age c o n t r o l p r e d o m i n a t i n g .

G r o w t h in r e a c t i v e d e m a n d a t t h e 66-ki lovol t level has b e e n 125,000 k v a r e a c h y e a r . I n a d d i t i o n t o p l a n n i n g for this load , k i lovar g e n e r a t i n g m a r g i n h a s b e e n p l a n n e d to p r o v i d e for con t ingenc ie s s u c h as t r a n s m i t t i n g l a r g e a m o u n t s of i n t e r c h a n g e p o w e r , o u t a g e of a m a j o r t r a n s -

Fig. 1. Reactive supply and demand at time of summer reactive peak, 3 pm, July 30, 1954

ι I R E S E R V E I

GENERATOR | CAPABILITY

J ι

2 0 0 0

1 8 0 0

1 6 0 0

1400

RS

1200

<

AV

1 0 0 0 CD UJ 8 0 0 8 0 0

6 0 0

4 0 0

2 0 0

0

2 2 0 KV B A N K S

AND L I N E S

G E N E R A T I O N A N D I N T E R ­

C O N N E C T I O N S 2 2 0 KV B A N K S

AND L I N E S 2 2 0 KV

L I N E CHARGING

2 2 0 KV L I N E

CHARGING

6 6 KV LINES, TRANSFORMERS BELOW 220 KV, DISTRIBUTION LINES AND CUSTOMER

L O A D

SYNCHRONOUS CONDENSERS

STATIC CAPACITORS

2° 2 2 0 KV

LINE CHARGING

SYNCHRONOUS CONDENSERS

STATIC CAPACITORS

Q

<

ο <

>-Ι ­ο

< ο rr < >

1930 1935 1945 1955

INSTALLED C A P A C I T Y

Fig. 2. Relationship between megavar capacity and megawatt demand

mission l ine o r s y n c h r o n o u s c o n d e n s e r , o r u n u s u a l l y h e a v y a i r - c o n d i t i o n i n g l o a d .

S t a t i c c a p a c i t o r s will s u p p l y t h e m a j o r i t y of this a n n u a l g r o w t h of r e a c t i v e d e m a n d in t h e fu tu re , as s h o w n in F ig . 2. S y n c h r o n o u s condense r s , w h i c h for m a n y yea r s p r o v i d e d for t h e r e a c t i v e l o a d g r o w t h a n d m a r g i n , a r e dec reas ing in r e l a t ive i m p o r t a n c e . T h i s d e c r e a s e is d u e in p a r t to c h a n g i n g cost r e l a t i o n s h i p b e t w e e n s y n c h r o n o u s con­densers a n d c a p a c i t o r s , a n d to t h e fact t h a t fewer long t r ansmiss ion l ines w h i c h r e q u i r e k i lova r a b s o r b i n g c a p a ­bili t ies of c o n d e n s e r s wil l b e a d d e d to t h e sys tem.

C a p a c i t o r s wil l b e a p p o r t i o n e d to t h e va r ious 2 2 0 / 6 6 -ki lovol t o p e r a t i n g a r e a s in a c c o r d a n c e w i t h t h e r eac t ive l o a d a n d rese rve r e q u i r e m e n t s . U n s w i t c h e d c i rcu i t in­s ta l la t ions will b e d e t e r m i n e d b y m i n i m u m load p o w e r fac tor o n c i rcui t s , a n d swi t ched c i rcu i t ins ta l la t ions will b e d e t e r m i n e d b y loca l v o l t a g e cond i t i ons . Specific s u b s t a t i o n ins ta l l a t ions will d e p e n d m a i n l y u p o n ava i l ab l e t r a n s f o r m e r t a p s , u p o n des i red v o l t a g e co r rec t ion , a n d u p o n r e q u i r e d c o r r e c t i o n of 66-ki lovol t sub t ransmiss ion vo l t age level . C a p a c i t o r s will b e p r o g r a m m e d for ins ta l la­t ion on 66-ki lovol t busses a t subs t a t ions after o p t i m u m c a p a c i t o r ins ta l l a t ions h a v e b e e n c o m p l e t e d on t h e dis­t r i b u t i o n v o l t a g e busses.

Digest of paper 56-2, "Planning Kilovars and Capacitors for the Southern California Edison System," recommended by the AIEE Committee on Transmission and Dis­tribution 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.

J. H. Drake and G. A. Davis are with the Southern California Edison Company, Los Angeles, Calif.

APRIL 1956 Drake, Davis—Kilovar Planning 355