Which of the following measures is primarily used to guard against electrical shock?

The primary measure used to guard against electrical shock is grounding. Grounding provides a path for electrical current to flow safely into the ground in the event of a fault, such as a short circuit or when a person comes into contact with a live conductor. This significantly reduces the risk of electrical shock by ensuring that excess current is directed away from individuals and into the earth, where it can dissipate harmlessly.

The concept of grounding is critical in electrical systems as it helps to stabilize voltage levels and provides a reference point for the electrical system, which can help in preventing overvoltages that might otherwise lead to dangerous situations. Furthermore, grounding ensures that equipment enclosures and circuitry remain at a safe potential, thereby preventing hazardous contact.

The other measures mentioned have different functions: insulation helps to prevent accidental contact with live parts within electrical devices; earthing often refers specifically to connecting parts of an electrical system directly to the ground for certain protective measures; and overcurrent protection helps limit the amount of current flowing through a circuit but does not directly prevent electrical shock. While all these measures play roles in electrical safety, grounding is unique in its direct impact on preventing shock hazards.