Enforcing precautions boils down to the individuals working on the three phase wiring system. When working on the site, always wear protective clothing. This may include arc flash suits, voltage-rated gloves and heavy-duty work shoes.
Always make sure that you turn off the power source for the circuit you are operating on before you start work. To increase your safety, kill the power for the entire system at the mains, preferably at the circuit breaker, if one is present, rather than at a switch along the circuit.
Working with high voltages requires special tools as well. The tools are usually insulated, and in some cases, double-insulated, meaning they have two protective layers. Another precaution is to always use the right tool for the right job. Never use your bare hands or any part of your body -- for example, never cut a wire with your hands or teeth.
Refer to wire color codes for three phase wiring systems when working on connections. The probable coloring of the wires would be black, red and blue for wires marked L1, L2 and L3 respectively. White and green are wires are for the neutral and the ground correspondingly. In case you have a newer 277/480V installation, the color coding would be in the form of brown, orange and yellow for L1, L2 and L3 respectively, with the neutral and ground remaining as white and green. Make sure you connect the right wire to the right terminals, which should be marked accordingly as L1, L2 and L3. The neutral would be marked as N and the ground would be marked with the traditional ground symbol.