EHV Substations & Transmission Lines EPC

AIS (Air Insulated Switchgear) is the traditional outdoor design where each piece of equipment — circuit breaker, isolator, CT, PT — is mounted separately on steel structures with air as insulation between conductors. It needs a lot of space because you need safety clearances between live parts. GIS (Gas Insulated Switchgear) puts everything inside metal-enclosed compartments filled with SF6 gas, which insulates much better than air. GIS is compact — a 132kV GIS bay can fit in 20% of the space an AIS bay needs. But GIS costs more upfront. GIS makes sense for urban locations where land is expensive.

Typically 4 to 6 months from ground breaking to CEIG approval. Civil works take about 6–8 weeks, equipment erection 4–6 weeks, control wiring and relay panels 3–4 weeks, and testing plus CEIG inspection another 2–3 weeks. These timelines assume the transformer and major equipment are already procured — transformer delivery lead time is usually the longest item at 12–16 weeks for custom ratings.

Yes, completely. We prepare all CEIG documentation — single line diagrams, GA drawings, earthing calculations, protection scheme write-ups, equipment test certificates, and the statutory application form. We coordinate the inspector's site visit, address any observations or corrections on the spot, and follow up until the approval certificate is in your hand.

Yes, bay extensions are a regular part of our work. When a solar park adds new capacity or an industry needs an additional feeder, we design and construct the new bay — including bus bar extension, breaker installation, CT/PT addition, and protection relay integration — without shutting down the rest of the substation. Hot-line work permits are coordinated with the DISCOM's operations team.

It depends on the voltage and current rating. For 33kV lines, we typically use ACSR Dog (100 sq.mm) or Panther (200 sq.mm). For 132kV lines, ACSR Panther or Zebra. For 220kV, ACSR Moose with twin or quad bundling. The conductor selection is based on thermal current rating, sag-tension calculations, and wind/ice loading for your specific terrain and span length.