SRI ® Make Unitised Sub-Station (USS) << Back

A Unitised Sub-Station (USS) also known as a Packaged Sub-Station (PSS) or Compact Sub-Station(CSS) is a cost effective,aesthetically pleasing, nutshell product. A USS comprises of various sub-station equipments housed inside a metal enclosure. The equipments include a step down transformer, a Vacuum Circuit Breaker (VCB) or a Ring Main Unit (RMU) on High Voltage (HV) side and Low Voltage (LV) distribution panel in LV side compartment. It is a pre-fabricated sub-station engineered to reduce size, increase safety and provide the customer with “One stop product” for all his power distribution needs.

With our whole gamut of Power Distribution products and being one of the biggest Panel manufacturers in India, manufacturing of USS is just an extension of our engineering prowess.

We at Shri Ram Group Of Industries manufacture USS upto 3 mVA 33 kV class with both Dry Type as well as Oil cooled Distribution transformer. These USS are particularly useful in areas where there is a space constraint and safety issues like basement of high rise buildings, steel plants, refineries, mines, malls, theatres, IT & ITES companies etc.

  • Technical Specifications
  • Salient Features
  • Standard Fittings
  • Optional Fittings

Technical Specifications

Rating Upto 3Mva
Duty Type Outdoor/Indoor, Ground Mounted Type
Voltage Class Upto 33Kv
No Of  Phases 3 phase
Degree of Protection IP 23D (Protection can be increased on request) IP54 for MV & LV compartments.
Temperature Class K 10
Earthing system Upto 26.3 kA
Medium Voltage Compartment
MV Switchgear 3.3 to 33 KV
Type of Switchgear LBS / SFU / Breaker / RMU
Insulation medium SF6 Gas or Vacuum
Tripping Fuse / Relay
Short Circuit Rating Up to 20 KA or as per customer requirement.
Transformer Compartment
Type of Cooling Oil Immersed / Dry Type
Rating 100 to 3000 KVA
Tank Hermetically Sealed, Corrugated Type or Conventional Air/Oil cooled Type
Low Voltage Compartment
MV Switchgear ACB’s, MCCB’s
Current rating Up to 3250 Amps
Voltage 433 Volts
No. of Poles 3 / 4
Short Circuit Rating 50 KA or as per customer requirement

Salient Features of SRI ® Make Unitised Sub-Station

Fully Compartmentalized Design.
Design Conforms to IS 14785, IS 14786, IEC 61330 standards.
Completely factory built with superior aesthetics.
Custom made to meet each and every requirement of customers conforming to National & International Standards.
Integrated In-House manufacturing of Transformers, switchgears and metal enclosure enables to keep quality and delivery under check.
Compact in size and minimal maintenance required.
Average Delivery Time: 45-60 Days
Facility to make 50-60 Nos USS per month.


Standard Design and Fixtures M.S./CRCA Sheet fabricated Enclosure as per IS 14786 Lifting Hooks
Perforated sheet & Air ventilation louvers in Transformer section Collapsible hinge mounted doors Easy removable canopy with protection from rain water
For safety, doors with alarm & tripping circuit Inter connecting MV & LV with cables& Bus Bars Powder coated paint, Shade – RAL 7032 or as per customer’s requirement
Illuminating lamps with MCB

Optional Fittings

M.V Compartments Transformer Compartment L.V Compartment
MV Draw out type Breaker On load tap changer with R.T.C.C panel & AVR APFCR Panel with capacitor Bank
H.T Metering / Load manager Pressure Release valve Feeder Pillar ( HRC Fuse/ MCCB Based)
Annunciator & Power Pack W.T.I & O.T.I with Alarm & Trip Contacts L.T MFM/Load manger
Earth fault , Over current relay Magnetic Oil Gauge with low level contacts. L.T microprocessor based trip unit
Scada or P.L.C compatible Bucholz Relay with Alarm & Trip Contacts L.T Earth fault & Over current relay