Introduction to the basic purpose and classification of grounding and zeroing

First, grounding is necessary for the proper functioning of electrical circuits. Second, it is essential for ensuring the safety of both people and equipment. Based on their functions, grounding can be categorized into four types: working grounding, protective grounding, protective earthing (zeroing), and repeated grounding.

Working grounding is crucial in low-voltage power systems, such as those operating at 380/220V. In these systems, four wires are typically drawn from the transformer—three phase lines and one neutral wire. These are used for both power distribution and lighting. The three-phase lines supply power, while the single-phase lighting uses one phase and the neutral line. To ensure safe and reliable operation, the system's neutral point is directly connected to ground, known as working grounding. This helps stabilize the system's voltage and limits the risk of high voltage entering the low-voltage side.

Protective grounding is used to prevent electric shocks by connecting the non-current-carrying metal parts of electrical devices—such as casings, frames, or structures—to the earth. This is especially important in ungrounded power systems where insulation failure could lead to dangerous voltages. Protective grounding ensures that any exposed metal parts remain at a safe potential, reducing the risk of injury. It is commonly applied to motor casings, switchgear, transformer housings, and other metallic components that may become energized due to faults.

Protective earthing, also known as zeroing, involves connecting the metal casing of electrical equipment directly to the neutral line of the power grid. This method is widely used in low-voltage systems below 1000 volts. If an insulation fault occurs, the fault current creates a short circuit between the phase and neutral, triggering protective devices like fuses or circuit breakers to quickly disconnect the power. This prevents the metal parts of the equipment from remaining energized for long periods, thereby protecting users from electric shock.

However, it's important to note that in some cases, mixing protective grounding and protective earthing can be dangerous. For example, if a device is protected by earthing but the grounding resistance is too high, the neutral line might carry a dangerous voltage, posing a risk to personnel. Therefore, in certain systems, only one method should be used consistently to avoid conflicts and ensure safety.

In summary, grounding and earthing are essential practices in electrical systems. They not only support the normal operation of circuits but also protect against electrical hazards. Understanding the different types and their applications helps in designing safer and more efficient electrical installations.