Compact Secondary Substations (CSS)
Smart, Safe & Space-Optimized Power Distribution
The TransVolt Compact Secondary Substation (CSS) — also known as a Packaged or Unitised Substation — is a factory-assembled, pre-tested, and ready-to-install power distribution solution. Designed for space-constrained and safety-critical environments, it integrates Medium Voltage (MV) switchgear, a distribution transformer, and a Low Voltage (LV) panel into a single, compact enclosure.
This plug-and-play configuration significantly reduces on-site civil work, cabling complexity, and installation time compared to conventional open-yard substations. Built in alignment with relevant standards, including IEC 62271 and IEC 60076, the TransVolt CSS ensures reliable and compliant performance.
Engineered with compartmentalized construction for enhanced personnel safety, the enclosure provides high IP protection and robust structural integrity to withstand harsh environmental conditions. Suitable for oil-immersed or dry-type transformers, the system incorporates optimized ventilation for efficient thermal management.
Technical Specifications
Electrical Parameters
Feature
Specification
Rated Power Range
250 kVA to 5000 kVA
Voltage Class
3.3 kV, 6.6 kV, 11 kV, 22 kV, and 33 kV
Frequency
50 Hz / 60 Hz
Vector Group
Dyn11 (Standard) or as per customer requirement
Tapping Range
±5% in steps of 2.5% (5 steps) or as per requirement
HV Protection
LV Protection
Insulation Level
Designed to withstand rated electrical impulses and surges
Core Material
High-grade CRGO silicon steel (ZDKH, ZDMH, MOH, or Amorphous).
Design
Step-lap construction to minimise no-load losses and noise levels.
Clamping
Rigidly clamped to withstand transport vibrations and electromagnetic forces.
Conductor Material
99.99% pure Electrolytic Grade Copper (Hindalco/Sterlite).
LV Winding
Foil winding technology often utilised for enhanced short-circuit strength.
Insulation
High-density pressboard and Kraft paper for oil-filled Epoxy cast or VPI for dry-type.
Transformer Coolingd
ONAN (Oil Natural Air Natural) or AN (Air Natural for Dry Type).
Enclosure Ventilation
Specially designed air ventilation louvers and perforated sheets to maintain thermal class K10.
Temperature Monitoring
8-channel RTD (EMCO make) for Dry Type with Fan, Alarm, and Trip outputs.
Cabinet Material
Robust Mild Steel (MS) cabinet to protect internal devices from environment.
IP Protection
IP23 to IP54 depending on compartment and cooling requirements.
Surface Treatment
Zinc-rich primer base for long-term rust prevention.
Paint Specification
Epoxy or Polyurethane (PU) dual-coat for protection for a minimum of 5 years.
HV Side
Ring Main Unit (RMU) or VCB with necessary CTs/PTs and protective relays.
LV Side
Customised distribution board with ACB, MCCBs, and metering equipment.
Safety
Internal arc-tested design, tamper-proof lockable doors, and load-balancing lifting hooks.
Interconnections
XLPE insulated cables or busbars between compartments.
Applicable Standards
Fully compliant with IEC 62271-202, IS 2026, and IS 1180.
Factory Testing
Pre-fabricated and fully tested for dielectric strength, temperature rise, and mechanical operation before shipment.
Field Readiness
Ready for commissioning immediately after HV and LV cable connections are made.
Space Optimisation
Requires 30–50% less space than conventional substations.
Rapid Deployment
Delivered as a single unit, reducing installation time by up to 20%.
Enhanced Safety
Completely enclosed and compartmentalised to protect the general public and operators.
Aesthetic Appeal
Compact and modern design suitable for urban and high-visibility locations.
Urban Infrastructure
Shopping malls, hospitals, hotels, and residential townships.
Heavy Industry
Casting, textiles, and manufacturing plants.
Renewables
Step-up stations for Solar and Wind farms.
Temporary Power
Construction sites and temporary exhibitions.
Transformer Type
Choice between Dry-type (VPI/Cast Resin) for indoor/rooftop or Oil-immersed for outdoor use.
Feeder Configuration
Number and rating of LV feeders can be tailored to specific site loads.
Remote Monitoring
Integration of SCADA-compatible relays and digital metering.