H.T. & L.T. Electrical Equipment
High-tension and low-tension electrical equipment — RMUs, VCBs, isolators, bus ducts and allied switchgear — supplied to project specification.
About H.T. & L.T. Electrical Equipment
HT (high-tension) equipment handles the incoming 11 kV, 22 kV or 33 kV supply; LT (low-tension) equipment distributes the 415 V output of the transformer. Between them they switch, isolate, meter and protect the substation that feeds a plant or building.
On the HT side this means vacuum circuit breaker (VCB) panels, ring main units (RMUs) for looped underground cable networks, isolators and earth switches, metering cubicles and HT cable terminations. Switchgear for 11, 22 and 33 kV systems is rated at the next standard voltage class – 12, 24 and 36 kV – and built to the IEC 62271 series. Gas-insulated RMUs, such as Schneider Electric's RM6 for underground secondary distribution up to 24 kV, put the ring switching in one compact unit. On the LT side we supply ACB and MCCB distribution boards and bus ducts that carry high current from the transformer to the main panel, built to IEC 61439.
Microtech supplies HT and LT equipment to your single-line diagram and utility requirements, coordinated with the transformer and installed by the same team.
Key specifications
| HT system voltages | 11 kV, 22 kV and 33 kV |
|---|---|
| Switchgear rated voltage | 12 kV, 24 kV and 36 kV class |
| HT equipment | VCB panels, RMUs, isolators, metering cubicles, cable terminations |
| RMU example | Schneider RM6 gas-insulated, up to 24 kV, short-time withstand up to 21 kA |
| LT equipment | ACB/MCCB distribution boards, bus ducts, LT panels |
| HT standards | IEC 62271-100 / -102 / -200 |
| LT standards | IEC 61439-1/2, IEC 61439-6 for busbar trunking |
Features & benefits
- Complete substation package from HT incomer to LT distribution
- VCB and RMU options to suit overhead or underground supply
- Interlocked isolators and earth switches for safe maintenance
- Bus ducts for compact, high-current transformer-to-panel links
- Protection coordinated with the transformer rating
- Supplied to utility-approved single-line diagrams
Where it’s used
- Industrial substations
- Commercial and residential complexes
- Hospitals and campuses
- Solar plant evacuation substations
- Underground cable ring networks
- Substation upgrades and capacity additions
Standards & compliance
H.T. & L.T. Electrical Equipment — FAQs
VCB panel or RMU – which do I need?
An RMU is compact and suits looped underground cable networks and package substations. A VCB panel gives more flexible protection and metering and suits larger industrial substations. We advise from your single-line diagram and utility requirements.
Why is 11 kV switchgear rated 12 kV?
Switchgear is rated at the highest system voltage it may see. For an 11 kV network that is the 12 kV standard class; for 22 kV it is 24 kV and for 33 kV it is 36 kV.
When should I use a bus duct instead of cables?
For high currents between the transformer and the main LT panel, a bus duct is more compact, easier to route and simpler to terminate than several parallel runs of cable.
