PERFORMANCE OF CURRENT TRANSFORMERS DURING TRANSIENTS

摘要

A current transformer used in a power circuit for initiating operation of a circuit breaker has a resistor in series with the burden on its secondary. This resistor is shunted by a set of contacts which close or open with the main contacts of the breaker. These secondary contacts are closed when the main contacts are closed and are open only when the main contacts are open. Opening of the secondary contacts places the resistor in series with the burden; this causes repid decay of the flux in the core to the residual level, rapidly making the transformer ready for further fault current when the main breaker contacts are reclosed. This arrangement will improve the transient performance of current transformers, but it is particularly effective with gapped core current transformers.