Series Connection of Current Transformer

Series connected CT
Figure 1: Series connected CT

Read: Current transformer DC saturation and time to saturate

Read: Potential transformer accuracy

Read: Zero sequence current transformer

Bushing CTs located on a same phase can be series connected to improve accuracy
Figure 2: Bushing CTs located on a same phase can be series connected to improve accuracy
CT2 will block CT1 current as load current is zero. Connection not recommended
Figure 3: CT2 will block CT1 current as load current is zero. Connection not recommended

Read: How to select taps for multi ratio current transformer?

Mismatched CT ratio cause CT2 to offer high impedance ‘Z’ to current flow. Connection not recommended
Mismatched CT ratio cause CT2 to offer high impedance ‘Z’ to current flow. Connection not recommended

Read: Adjusting current transformer ratio

References

[1] Protective relaying, Principles and applications; J Lewis Blackburn; Thomas J. Domin

[2] The art and science of protective relaying; C Russel Mason