Ground (electricity)

In electrical engineering, ground or earth may refer to reference ground – a reference point in an electrical circuit from which voltages are measured, earth ground – an electrically neutral node that has a lot of available charges (e.g. the physical ground of Earth), or common ground – a common return path for electric current (also called neutral in electric power systems). Ground current or earth current is the current that flows through a reference ground, earth ground, or common ground. To ground or to earth an object is to electrically connect the object to a reference ground, earth ground, or common ground. Electrical circuits may be grounded for several reasons. A protective earth conductor (PE conductor) is a conductor that is used for electrical bonding, that is, connecting an electrical equipment from its exposed and conductive but normally unenergized part to common ground. If the conductor is a wire, it is also called ground wire or earth wire. Ground wire is often used for lower voltage systems and is often colored green, or green and yellow, per standard. Electrical bonding can protect users from electrical shock hazards. If internal insulation fails and the equipment is turned on, the exposed conductive parts may have dangerous voltages. Connection of exposed conductive parts to a PE conductor provides a low-impedance path for current to flow back to the incoming neutral. This results in a fault and allows circuit breakers (or RCDs) to interrupt power supply. The current that flows through the low-impedance path is high and will usually trip the breaker or melt the safety fuse if any. Even if the circuit does not break due to failures, the current still only flows mainly through the PE conductor instead of the user upon touching the exposed conductive part. A PE conductor is...