Which of the following methods is not suitable for establishing bonding connections for high voltage circuits?

The answer indicates that using a locknut on the outside and a bushing on the inside of the metal enclosure is not a suitable method for establishing bonding connections for high voltage circuits. This is primarily because bonding connections need to maintain low resistance and ensure efficient dissipation of fault currents.

In high voltage applications, ensuring a reliable and strong electrical connection is paramount. Locknuts and bushings may provide mechanical stability but are typically not designed to offer a low-resistance electrical bond. They can introduce potential points of failure where high voltages can create arcing or an inadequate connection under fault conditions.

In contrast, methods like welded connections, grounding screw connections, and continuous metallic paths are preferred in high voltage applications because they effectively reduce resistance and enhance the overall integrity of the bond. Welding creates a permanent, low-resistance joint, grounding screws provide secure connections designed for grounding applications, and continuous metallic paths ensure no interruptions in conductivity, promoting safety and efficiency. Understanding these principles is crucial for ensuring safety and performance in electrical systems, especially those handling high voltage.