Prior to connecting three-phase cables, what must the phase cables be?

The correct approach before connecting three-phase cables is to ensure that the phase cables are properly identified by means of coding, marking tape, or tagging. This identification is crucial because it helps avoid confusion and ensures that each phase is connected correctly. Misconnections could lead to equipment damage, inefficiency, or even dangerous conditions.

When each phase is clearly identified, it becomes much easier to maintain consistency in how the connections are made, which is vital for both electrical functioning and safety. Proper labeling facilitates troubleshooting and maintenance tasks in the future, as technicians can quickly ascertain which phase corresponds to which circuit.

In the context of the other options, leaving cables unidentified could lead to significant risks, while securing them with zip ties does not address the critical need for proper identification. Bundling the cables together may improve physical organization, but it does not substitute for the necessary marking that prevents errors during the connection process.