How should portable electric tools be connected to a power source for safety?

Using a three-wire cord is the safest method to connect portable electric tools to a power source. This type of cord includes three wires: one for the live connection, one for the neutral connection, and a third wire that acts as a ground. The ground wire is crucial for safety, as it helps to prevent electrical shock by providing a pathway for excess current to safely discharge into the ground in case of a fault.

In addition to providing a means for grounding, three-wire cords are designed to handle higher power loads, making them suitable for the demands of most portable electric tools. They also typically come equipped with a plug that ensures it can only be connected to compatible outlets, further enhancing safety.

Connecting tools using any available power cord could lead to using cords that are not rated for the tool's power requirements, increasing the risk of overheating or electrical failure. Relying solely on extension cords lacks the inherent grounding that a three-wire setup provides, and connecting a tool directly without any cord negates the safety features of a grounded system altogether.