Improving electric railway fault clearing times

Abstract

A K E R S d e s i g n e d i n 1913 for sectionalizing t h e 1 1 / 2 2 -k v 3-wire trolley a n d feeder circuits o n t h e N e w H a v e n R a i l r o a d electrification h a d b e c o m e i n a d e q u a t e b y 1936 b e c a u s e of l i m i t e d i n t e r r u p t i n g c a p a c i t y to c l e a r line faults fast e n o u g h t o i n s u r e system stability a n d reliability. A l t h o u g h these n e v e r w e r e d e signed to h a n d l e t h e e n t i r e fault i n t e r r u p t i o n d u t y , s p a c e a n d w e i g h t l i m i t a t i o n s i n t h e s w i t c h i n g s t a t i o n s a n d s u p p o r t i n g s t r u c t u r e s r u l e d o u t t h e i r r e p l a c e m e n t w i t h m o d e r n circuit b r e a k e r s of c o n v e n t i o n a l d e s i g n for faster fault c l e a r i n g b y l i n e c i r c u i t b r e a k e r s d i r e c t l y . T h e oil c i r c u i t b r e a k e r s a r e k n o w n as " b r i d g e -t y p e " c i r c u i t b r e a k e r s b e c a u s e of t h e i r l o c a t i o n o n t h e a n c h o r b r i d g e s s p a n n i n g t h e r a i l r o a d t r a c k s a n d c a t e n a r y c o n t a c t system. F i g u r e 1, of a t y p i c a l s w i t c h i n g s t a t i o n , c l e a r l y i n d i c a t e s t h e s p a c e a n d w e i g h t l i m i t a t i o n s i n v o l v e d b e c a u s e of t h e l o c a t i o n of t h e c i r c u i t b r e a k e r s o n t h e a n c h o r b r i d g e s . D e l a y e d t r i p p i n g of t h e b r i d g e -t y p e oil c i r c u i t b r e a k e r s w a s a c c o m p l i s h e d b y m e a n s of a " r e s i s t a n c e -i n s e r t i o n " s c h e m e of fault c l e a r i n g . I n this s c h e m e " m a s t e r " relays p r e v e n t e d t r i p p i n g of trolley a n d feeder c i r c u i t b r e a k e r s i n case of a fault u n t i l resistances l o c a t e d a t t h e p o w e r s u p p l y p o i n t s w e r e c u t -i n series w i t h t h e lines. I n this m a n n e r t h e fault c u r r e n t s i n t e r r u p t e d b y t h e c i r c u i t b r e a k ers w e r e r e d u c e d t o less t h a n 3,000 a m p e r e s , r m s , b u t t h e s c h e m e r e q u i r e d a p p r o x i m a t e l y 0.7 s e c o n d of t i m e t o c l e a r t h e faults. A s m o s t of t h e fault c l e a r i n g t i m e w a s c o n s u m e d b y t h e t i m e d e l a y resistance-insertion s c h e m e , a n y a p p r e c i a b l e r e d u c t i o n in this t i m e r e q u i r e d i m m e d i a t e Digest of paper 48-170, "Circuit Breaker Modernization and Faster Fault Clearing on Single-Phase Electrified Railroad," recommended by the AIEE committee on switchgear and approved by the AIEE technical program committee for presentation at the North Eastern District meeting, New Haven, Conn., April 28-30, 1948. Scheduled for publication in AIEE TRANSACTIONS, volume 67, 1948. H. F. Brown is with the New York, New Haven, and Hartford Railroad, New Haven, Conn. H. A. Travere and C A. Woods, Jr., are both with Westinghouse Electric Cor poration, East Pittsburgh, Pa. t r i p p i n g of...