What Is a 132/11kV Transformer?
A 132/11kV transformer is a high-to-medium voltage step-down transformer commonly used in power transmission and distribution networks. Its primary function is to reduce voltage from 132,000 volts (high voltage) to 11,000 volts (medium voltage), making it suitable for downstream industrial or utility distribution.
These transformers are essential for regional substations, where power from long-distance transmission lines needs to be stepped down for further distribution to cities, industries, or renewable energy installations.
General Specifications
| Parameter | Description |
|---|---|
| Rated Voltage (Primary) | 132 kV |
| Rated Voltage (Secondary) | 11 kV |
| Frequency | 50 Hz or 60 Hz |
| Phase | 3 Phase |
| Cooling Type | ONAN / ONAF / OFAF |
| Transformer Type | Oil-Immersed (or Dry-type on request) |
| Vector Group | Dyn11 / YNd11 / YNyn0 (based on system) |
| Tapping Range | ±10% or ±5% with OLTC or Off-load tap |
| Rated Power Capacity | 10 MVA – 100 MVA (varies by application) |
| Insulation Class | Class A / F / B |
| Standards | IEC 60076, ANSI, BS, IS |
Key Components
1. Core
- Material: Cold rolled grain-oriented silicon steel
- Type: Step-lap or mitered core construction
- Purpose: Minimizes core losses and magnetostriction
2. Windings
- Material: High-conductivity copper (or aluminum upon request)
- Construction: Layered, disc or helical windings
- Insulation: Kraft paper, epoxy, or NOMEX-based insulation
3. Tank and Radiators
- Hermetically sealed or conservator-type design
- Equipped with cooling radiators, oil level indicators, and breather
4. Bushings
- Primary: Condenser-type bushings rated for 145 kV insulation level
- Secondary: 17.5 kV class bushings, porcelain or polymer type
5. On-Load Tap Changer (OLTC)
- Installed for voltage regulation under load
- Typically provides ±10% adjustment in 17 steps
Cooling Systems
The 132/11kV transformer may use one of the following cooling types:
- ONAN (Oil Natural Air Natural): For standard capacity range
- ONAF (Oil Natural Air Forced): With fans to increase cooling performance
- OFAF (Oil Forced Air Forced): For high-capacity transformers above 50 MVA
Protection and Monitoring
Modern transformers include comprehensive protection systems:
- Buchholz Relay (gas accumulation detection)
- WTI / OTI: Winding and Oil Temperature Indicators
- Pressure Relief Device (PRD)
- Magnetic Oil Level Gauge (MOG)
- Sudden pressure relay
- Differential and Overcurrent Protection (via external relays)
Smart options include:
- SCADA compatibility
- Remote oil temperature monitoring
- IoT sensor-based predictive maintenance
Installation Considerations
- Foundation Requirements: Level concrete base with oil containment trench
- Earthing: Dedicated grounding terminal, as per IEEE 80
- Clearance: Meet national safety standards (IS, IEC) for HV/MV equipment
- Transport: Requires special handling; may ship with accessories detached
- Commissioning: Includes IR tests, ratio test, winding resistance, and oil BDV
Applications
The 132/11kV transformer is widely used in:
- Utility substations for regional grid interconnection
- Industrial plants requiring high-volume medium-voltage power
- Solar farms and wind farms feeding power to 132kV transmission grid
- Metro stations and airports
- Mining operations, oil refineries, and steel mills
- Energy storage and battery systems as grid-coupling interface
Advantages
- High efficiency (typically >99%)
- Long lifespan with proper maintenance (>25 years)
- Designed to handle short-circuit forces and overloads
- Customizable with smart monitoring and protection features
- Compliant with global grid code standards
Maintenance Tips
- Regular oil testing (BDV, moisture content, acidity)
- Inspection of gaskets, breathers, and tank seals
- Periodic testing of CTs, PTs, relays, and tap changers
- Visual checks for leaks, corrosion, and unusual noise
- IR thermography for hotspot detection
Conclusion
A 132/11kV transformer is a critical part of power infrastructure, providing reliable voltage transformation for safe and efficient energy delivery. Whether you’re expanding a utility grid or powering an industrial facility, selecting the right transformer with the proper technical specification ensures long-term performance and operational safety.
For tailored transformer solutions, project-specific configurations, or turnkey substation packages, partnering with an experienced manufacturer ensures that your energy infrastructure is future-ready.