To limit short-circuit current in a power system are used

The correct answer is: D. reactors.

Reactors are used to limit short-circuit current in a power system by absorbing the excess current. They do this by creating a magnetic field that opposes the current flow. This causes the current to decrease, which helps to protect the system from damage.

Earth wires are used to provide a safe path for current to flow to the ground in the event of a fault. Isolators are used to disconnect parts of a power system for maintenance or repair. H.R. fuses are used to protect electrical equipment from damage caused by overloads or short circuits.

Here is a more detailed explanation of each option:

• Earth wires: Earth wires are used to provide a safe path for current to flow to the ground in the event of a fault. They are usually made of copper or aluminum and are connected to the ground at various points throughout the power system.
• Isolators: Isolators are used to disconnect parts of a power system for maintenance or repair. They are usually made of porcelain or glass and are designed to withstand high voltages.
• H.R. fuses: H.R. fuses are used to protect electrical equipment from damage caused by overloads or short circuits. They are usually made of a thin wire that melts when the current exceeds a certain value.
• Reactors: Reactors are used to limit short-circuit current in a power system by absorbing the excess current. They do this by creating a magnetic field that opposes the current flow. This causes the current to decrease, which helps to protect the system from damage.