A typical ring mainframe consists of the following key components that perform switching functions:

As switchgear, the Ring Main Unit (RMU) performs the following key functions in a power distribution network:

• Circuit Control: The RMU is used to switch circuits from one line to another in a circulating network.
• Isolation: This is another key function performed by the RMU. It is crucial for isolating a faulted section from the rest of the circuit.
• Protection: Because the RMU consists of multiple devices, such as circuit breakers, fuses, and earthing switches, it provides protection against overload, short-circuit, or ground-fault currents.

Ring Main Units are considered multifunctional and important equipment in secondary power distribution networks, primarily used in urban and industrial areas.

Ring main units (RMUs) are used in medium-voltage secondary distribution networks for isolation, protection, and control purposes. Common applications include: