When is a cable considered isolated and safe to work on?

A cable is considered isolated and safe to work on when it is deenergized and the elbows are parked on grounded bushings. This scenario indicates that the cable is not only unpowered, reducing the risk of electric shock, but also that any potential energy or sources of electrical current are effectively controlled. Parking the elbows on grounded bushings ensures that any capacitively coupled voltages are discharged and that the cable is properly grounded, further enhancing safety for workers.

In contrast, the other options do not provide a safe working environment. A cable submerged in oil does not necessarily guarantee that it is isolated from energizing sources. An active circuit implies that electricity is flowing, which poses a significant risk of shock or injury. Likewise, wrapping a cable in insulation does not confirm that it is deenergized or that there isn't any residual or induced voltage present. Insulation serves to prevent accidental contact with live components but does not determine whether the cable is safe to work on without following proper isolation and grounding protocols.