GEK-45464
Tabl e I bel ow l i sts the combi n ed overal l l o g i c and external connect i on s di a g rams and
addi ti onal features o f each rel ay:
Rel ay Model
SB C23A
SBC23B
SB C2 3 C
TABLE I
External Connec t i ons
a nd Lo gi c D i a g ram
Fi g u re 2
Fi g u re 3
Fi g ure 4
Addi t i onal Featu res
Seco nd, Non-Isol a ted
Contac t
Con tac t on IT Un i t
Conve rte r
X
Opti onal
X
Opt i onal
X
Note that the SBC23A i ncl u des the addi t i onal non-i sol a ted conta c t o n the IT un i t
wh i ch i s norma l l y connected to pro v i de a seal -i n a ro u nd the i n i ti a t i n g con tacts
( B FI, 62X o r 62Y).
Th i s seal - i n contact i s opt i onal i n the SB C2 3B and SBC23C
model s, and i f u s ed, the norma l l y-i sol a ted IT contact is no l onger i sol a ted.
Under normal cond i t i ons, the SB C rel ays do no t have DC appl i ed. Thus, the S B C i s
norma l l y i mmune to any response to envi ronmenta l e l ectr i cal trans i en ts.
DC i s
appl i ed v i a B FI o r 62X functi ons onl y when a fau l t occ u rs o n a l i ne a s so c i a ted w i th
the breaker be i n g pro tec ted.
The powe r s uppy i n these rel ays i s so des i gned that the DC vol ta ge mu s t exceed 6 0%
o f the nomi nal vol tage rat i ng i n order for the rel ay to ope ra te.
Th i s fea t u re
prevents fa l se t r i ps from capac i ta nce di scha rge o r from the vol ta ge-di v i de r e ffec t
o f the grou nd-faul t l amps on the DC bus i n the event tha t the DC i nput termi na l o f
t h e S B C i s acc i dental l y grounded.
APPLICATION
The Type S B C sta t i c breaker-fa i l u re rel ays a re i n tended fo r appl i ca t i on on a per
breake r bas i s.
That i s, t h e re i s one breake r-fa i l u re rel ay a s soc i a ted w i th eac h
breake r i n a bus a rray. On th i s bas i s, the c u rren t i nputs to a pa rti cul a r SB C rel ay
mus t come from cu rre nt tra ns formers ( CT•s ) that meas u re the c u r re n t i n the
a ssoc i a ted breaker. The t r i p o u tpu ts must be routed to i n i t i a te the tr i ppi n g ( or
tra ns fe rred tr i ppi n g ) o f al l breake rs n ec es s a ry to cl ear the fau l t upon fa i l u re o f
the breaker a s soc i a ted wi th the SB C rel ay. Th i s rou t i n g wi l l depend upon the bus
a nd breake r arra ngemen t.
The l i s ti n g i n Tabl e II covers the bu s a rra ngements that a re i n common use. They
a re the s i ngl e-bus s i ngl e-breaker, do ubl e-bus do ubl e-breake r, breaker-a nd-a -ha
1
f,
a nd r i ng bus a rra ngements, s hown i n Fi gures 5, 6, 7 a nd 8 re spec t i vel y.
Eac h
l i st i ng i n Tabl e II i ndi ca tes the a ss umed fau l t l oca t i on, the breaker that i s
a s s umed to h ave fa i l ed, the conta c t i n i t i a t i on that acti vates the SBC, a nd wh i c h
breakers o r l ock-o u t rel ays shoul d be tri pped by the B FT contac ts. For exampl e, i n
a s i ngl e-bus s i ngl e -breake r a rra ngement, ( Fi g ure 5 ) , i f breake r #2 i s to be
protec ted, the SBC rel ay rec e i ves the current a s soc i a ted w i th breaker #2.
The
con tac t i n i t i a t i on is from the pro tect i ve rel ays o f l i ne B. If breake r #2 fa i l s for
a faul t a t Fl , the SBC rel ay opera tes and the B FT contact #1 t r i ps the bus l ockout
re l ay.
Fo r a nother exampl e, cons i de r the r i ng bus a r ra ngement that i s s hown i n
Fi g u re 8. If breaker #1 i s to be protec ted, the S B C rel ay rece i ves the c u rren ts
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