The metal box of the distribution box, the electrical installation board, and the metal base and casing of the electrical appliances in the box must be grounded. The protective neutral wire should be reliably connected through the terminal board. A standard mechanical light switch only interrupts the hot, or ungrounded, wire to turn a light on or off. If it's not wired correctly, you could run into overheating or power issues. Always double-check your connections and follow local wiring standards to stay compliant and safe. If the neutral wire is broken, this flow is disrupted, potentially. A neutral wire allows the three phase system to use a higher voltage while still supporting lower voltage single phase appliances.