330kV Oil-Immersed Three-Phase Three-Winding Power Transformer

Our 330kV oil-immersed three-phase three-winding off-circuit tap-changing power transformers are designed for complex grid applications requiring multi-voltage distribution within a single unit.

• Integrated three-winding design handles HV, MV, and LV simultaneously, simplifying substation layouts and reducing footprint and investment costs.

• Precisely optimized impedances: HV-MV at 24%–26%, HV-LV at 14%–15%, MV-LV at 8%–9% for effective short-circuit control and stable power flow.

• HV options at 330kV and 345kV with ±2×2.5% off-circuit taps; LV options at 10.5kV, 13.8kV, and 15.75kV.

• No-load current as low as 0.32% with optimized losses ensures high operational economy.

• YNyn0d11 vector group with oil-immersed construction for proven reliability, ideal for regional hub substations and large industrial plants.

Core Positioning

This series comprises highly integrated, multi-functional hub-type power transformers designed for 330kV extra-high voltage transmission networks. Capable of energy distribution and transformation among high-voltage, medium-voltage, and low-voltage levels within a single unit, they are particularly suitable for complex applications such as regional grid interconnection substations and central substations for large industrial plants requiring multiple voltage class power supply.

Technical Parameters

(MVA) Rated Capacity	Rated Voltage and Tapping Range			Vector Group	No Load Current (%)	Short-circuit Impedance (%)	No load Losses (kW)	On load Losses (kW)
	HV (kv)	Tapping Range	LV (kv)
90000	330 345	±2×2.5	10.5 13.8 15.75	YNyn0d11	0.37	HV~MV: 24~26 HV~LV: 14~15 MV~LV: 8~9	42	302

120000					0.37		53	374

150000					0.34		63	442

180000					0.34		72	507

240000					0.32		89	629

Core Advantages and Features

1. Integrated Multi-Voltage Transformation Capability:

- The three-winding design enables a single unit to simultaneously handle power transfer and distribution among high voltage (330/345kV), medium voltage (10.5/13.8/15.75kV), and low voltage (derivable from impedance relationships). This significantly simplifies primary substation layouts, reduces footprint, and lowers overall investment costs.

2. Precise Impedance Matching and Power Flow Control:

- The short-circuit impedance between windings (HV-MV: 24~26%, HV-LV: 14~15%, MV-LV: 8~9%) is meticulously designed and optimized. This effectively coordinates short-circuit current levels on each side, controls power flow between different voltage levels, and ensures the stable, coordinated operation of multi-tier grids.

3. Flexible Standard Voltage Options and Voltage Regulation:

- The high-voltage side offers standard voltage options of 330kV and 345kV, equipped with ±2×2.5% off-circuit taps to adapt to different regional system nominal voltages and operational fluctuations.

- The low-voltage side provides three common industrial and distribution voltage levels: 10.5kV, 13.8kV, and 15.75kV, meeting diverse end-user connection requirements.

4. High Reliability and Cost-Effectiveness:

- Features a classic three-phase oil-immersed design with proven, reliable insulation and cooling performance.

- Utilizes the standard YNyn0d11 vector group, ensuring strong compatibility and facilitating relay protection configuration.

- Low no-load current (0.32%-0.37%) and optimized no-load/load losses contribute to high operational economy.

Typical Applications

- Main transformers for 330kV/110kV/(10kV or 35kV) regional hub substations.

- Main step-down transformers for the general substations of large-scale industrial plants (e.g., steel, chemical, data centers), enabling direct power supply from EHV to multiple in-plant voltage levels.

- Start-up/standby transformers or tie transformers for power plants.

- Grid-connection transformers for renewable energy (e.g., wind, solar PV) collection and step-up substations.

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