HV

HV stands for high voltage and is used in electrical engineering and power systems to describe voltages high enough to pose significant risks of electric shock and arcing. It denotes equipment and systems that operate above the levels typical of consumer or light industrial electrical installations, and it carries specialized design, insulation, and safety requirements.

Definitions of HV vary by region and standard. A common generic stratification is: low voltage up to about 1 kV AC or 1.5 kV DC; medium voltage from roughly 1 kV to 35 kV; high voltage from about 35 kV to 230 kV; and extra-high voltage from 230 kV and above. Some standards further distinguish ultra-high voltage for voltages well above 800–1000 kV. Exact thresholds depend on national regulations and the context, such as transmission versus distribution or equipment ratings.

HV systems are primarily used for long-distance transmission and for transmitting power at high levels to reduce losses before stepping down to distribution voltages. Common HV equipment includes transformers, switchgear, insulators, cables, and surge arresters. Technologies such as high-voltage direct current (HVDC) are employed for certain long-distance or submarine links, where HVAC transmission would be less economical or feasible.

Safety and engineering considerations for HV include insulation coordination, adequate creepage and clearance distances, proper grounding, and protective relaying. Design aims to prevent insulation breakdown, arcing, and unintended contact, while managing switching transients and interference. Personnel working on HV installations require specialized training, procedures, and personal protective equipment.

Measurement and testing of HV systems use specialized instruments such as HV probes, insulation resistance testers, dielectric withstand (hipot) tests, and partial discharge monitoring. Standards bodies such as IEC and IEEE publish guidelines on insulation coordination, clearances, testing, and safety practices.