Need to check ON or OFF state of a wire using non-invasive method
A current transformer senses AC current through one winding, and flux-transfers current to its other winding: that's conventional transformer action. To confine the flux, some high-permeability material is often used.
The primary winding is usually one, single turn (green in the photo below). It doesn't look like a turn, because the wire you're trying to sense simply passes through the centre of the transformer once. This would be &quot;anyone wire of three-phase&quot;:

from:Magnelab UCT-0300-020 Solid Core Current Transformer
The secondary winding having many turns is potted around the core. In the photo, it exits the transformer as twisted white-black wires. This winding is terminated in a resistor. Voltage across this resistor is AC, whose amplitude and phase is proportional to current flowing in the primary winding.
Average voltage across the resistor is zero. With no primary current flowing, AC voltage across the resistor is zero.
For your application, some electronics is required to detect when the secondary winding AC voltage exceeds a desired voltage, perhaps in separate stages:

convert AC-to-DC
detect when DC voltage exceeds a threshold DC voltage set by you
convert to logic level: 0V or +5V