Mediumvoltage

Medium voltage (MV) denotes the portion of the electric power distribution system operating at voltages above low voltage and below high voltage. Common ranges: 1 kV to 52 kV, with many utility networks using 1–35 kV.

MV is used to distribute electricity from generation or transmission substations to local distribution transformers or large industrial customers. In practice, MV networks employ overhead lines or underground cables, supported by substations that house MV switchgear and protection equipment.

MV switchgear includes circuit breakers, disconnectors, and contactors for safe isolation and fault interruption at MV levels. Step-down transformers reduce MV to low voltage (typically 0.4 kV) for end use.

Protection and control systems—relays, fault indicators, and SCADA—monitor voltage, current, and fault levels and coordinate isolation. Design considerations include insulation coordination, clearance, short-circuit rating, reliability, and safety.

MV networks can be configured as radial feeders, looped or meshed networks to improve reliability. Standards from IEC and IEEE, among others, cover equipment performance, testing, and safety, including voltage classes, clearance requirements, and insulation levels. The term MV is sometimes region-specific; definitions vary by country and organization, but the general concept remains consistent.