What Is a Compact Substation (TNB Type)?
A Compact Substation (CSS) is a fully enclosed prefabricated unit that integrates a medium-voltage switchgear, distribution transformer, and low-voltage switchboard into one weatherproof enclosure. The TNB-compliant CSS is specifically engineered to meet the design, safety, and installation requirements of Tenaga Nasional Berhad (TNB) — Malaysia’s national electricity utility.
Used widely in Malaysia’s power distribution system, TNB-style compact substations offer fast deployment, space efficiency, and reliable operation in urban, commercial, and industrial environments.
TNB Compact Substation Standards
Compact substations designed for use in TNB networks must comply with the following:
- TNB Technical Guidebook (latest edition)
- IEC 62271-202 – High-voltage switchgear and controlgear – Prefabricated substation
- IEC 60076 – Power transformers
- TNB Specification No: TNBES 198, 201, 203 (project-dependent)
- Suruhanjaya Tenaga (Energy Commission) electrical safety code
- Local authority approvals (e.g., SIRIM, ST registration)
Typical Configuration of TNB Compact Substation
| Component | Description |
|---|---|
| MV Switchgear | 11kV SF6-insulated RMU (typically 3 or 4-way), TNB-approved brand |
| Transformer | 315–1000 kVA, 11/0.433kV oil-immersed sealed type (ONAN) |
| LV Switchboard | Outgoing MCCBs, metering panel, CTs, and terminals for low-voltage loads |
| Enclosure | Compartmentalized mild steel or stainless-steel structure (IP54–IP65) |
| Ventilation | Natural or forced air, louvers, and filters |
| Cable Termination | Bottom-entry cable ducts, earthing bar and links |
| Protection | Surge arresters, protection relays, fault indicators |
| Lighting & Socket | Internal service lighting, 13A plug, exhaust fan (optional) |
Standard Ratings
| Specification | Value |
|---|---|
| Rated Power | 315 kVA / 500 kVA / 630 kVA / 1000 kVA |
| Primary Voltage | 11 kV |
| Secondary Voltage | 400/230 V |
| Frequency | 50 Hz |
| Cooling | ONAN (Oil Natural Air Natural) |
| Insulation Class | Class A / B |
| Enclosure Protection | IP54 (minimum), IP65 (optional) |
| Temperature Rise | ≤ 60°C on windings |
| Earthing | TN-S or TT system compliant |
Design Features of TNB-Approved Compact Substation
- Three-compartment structure (MV, Transformer, LV) with individual access doors
- Internal arc-tested RMUs with SF6 insulation
- Corrosion-resistant enclosure with epoxy powder coating
- HV & LV compartments separated by metallic barriers
- TNB-type lock and interlock systems for safety
- Forced-air ventilation optional in high-load zones
- Lifting hooks, base frame, and anti-vibration pads for transport and installation
- Pad-mounted or skid-mounted options available
Application Areas
TNB Compact Substations are widely used in:
- Residential developments (terrace housing, condominiums)
- Commercial areas (malls, supermarkets, retail parks)
- Light industrial parks and SME zones
- Government facilities and schools
- Urban substations and transformer upgrading projects
- Renewable energy projects connected to the 11kV grid
- Temporary power supply in construction and mobile applications
Advantages of TNB Compact Substation
Space-saving: All-in-one design ideal for urban or limited-space environments
Quick Installation: Factory-assembled and pre-tested before delivery
TNB Compliance: Meets all utility specifications for fast approval
Safety Assured: Arc-proof, compartmentalized, and interlock-secured
Minimal Civil Work: Requires only a level concrete pad
Customization: Available with solar-ready features or hybrid modules
Low Maintenance: Sealed transformer and RMU reduce site servicing needs
Maintenance & Inspection
TNB recommends periodic inspection and maintenance to ensure substation reliability:
- Visual inspection of transformer tank, bushings, and oil level
- Cleaning of air vents and filters in the enclosure
- Infrared scanning of LV terminations (annually)
- Functional testing of MCCBs, relays, and indicators
- Oil dielectric strength (BDV) test every 3–5 years
Price Range in Malaysia (2024–2025)
As of current market estimates, a TNB-compliant 315–1000 kVA compact substation costs approximately:
RM 85,000 – RM 180,000
(subject to configuration, transformer rating, RMU brand, and materials)
The Compact Substation TNB type is the ideal solution for medium-voltage to low-voltage step-down transformation in Malaysia. Designed to meet TNB’s strict standards, these substations offer reliable performance, compactness, and easy integration into residential, commercial, or light industrial zones.
With factory-tested modular design, built-in safety features, and full compliance with TNB and IEC requirements, compact substations are the smart choice for modern power distribution infrastructure in Malaysia.