15
Instrument
transformers
Current transformers (CTs)
Figure 5: Type SDV7 distribution circuit
breaker with interphase barriers and
bushing current transformers installed in
primary compartment on page 16 illustrates
bushing (toroidal) CTs installed in the
primary compartment of a type SDV7
distribution circuit breaker. The roof
bushings pass through the CTs. Up to two
CTs may be mounted around each roof
bushing. The bushing CT connections are
wired to separate terminal blocks located in
the low-voltage operator compartment.
Hazardous voltages.
Will cause death, serious injury or property damage.
Do not operate current transformers with the secondary open circuited.
Current transformers must be either connected to a load or short circuited.
Current transformer secondary circuits also must be grounded.
Phase barriers
Phase barriers are provided on all 27.6 kV
and 38 kV class type SDV7 distribution
circuit breakers as shown in Type SDV7
distribution circuit breaker with interphase
barriers and bushing current transformers
installed in primary compartment on page
16. These plates of insulating material are
attached to the circuit breaker housing and
provide suitable electrical insulation
between the vacuum interrupter primary
circuits.
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