220kV Oil-Immersed 3-Phase 2-Winding NLTC Power Transformer

Our 220kV oil-immersed three-phase two-winding off-circuit tap-changing power transformers are designed for high-voltage grids requiring cost-effective and reliable power transmission.

• Rated from 31.5 MVA to 240 MVA with HV options at 220kV and 242kV.

• ±2×2.5% off-circuit tapping range; LV options from 6.3kV to 13.8kV.

• No-load current as low as 0.26% with optimized losses ensures high operational economy.

• YNd11 vector group with 12%–14% short-circuit impedance balances fault current limitation and voltage stability.

• Mature oil-immersed construction ideal for regional substations, renewable energy step-up stations, and large industrial enterprises.

Products Description

This series is a cost-effective, reliable, and structurally straightforward standard two-winding main power transformer designed for 220kV high-voltage grids. With its mature, proven design and excellent operational economy, it is widely used in regional substations, end-user applications, and renewable energy power plants, serving as a core and fundamental component for power transmission between high-voltage grids and medium-voltage distribution networks.

Technical Specifications

(MVA) Rated Capacity	Rated Voltage and Tapping Range			Vector Group	No Load Current (%)	Short-circuit Impedance (%)	No load Losses (kW)	On load Losses (kW)
(MVA) Rated Capacity	HV (kv)	Tapping Range	LV (kv)	Vector Group	No Load Current (%)	Short-circuit Impedance (%)	No load Losses (kW)	On load Losses (kW)
31500	220 242	±2×2.5	6.3 6.6	YNd11	0.45	12~14	15	115
40000					0.45		18	134
50000					0.42		21	161
63000					0.42		25	188
75000			10.5 13.8		0.38		29	213
90000					0.35		34	246
120000					0.35		41	304
150000			10.5 13.8		0.32		49	360
160000					0.31		51	378
180000					0.29		56	413
240000					0.26		70	484

Core Advantages and Features

1. Mature, Reliable, and Economical:

- Features a classic two-winding, oil-immersed, off-circuit tap-changing design. The structure is mature and proven, with simple operation and maintenance, offering significant advantages in total lifecycle cost.

- The high-voltage side supports standard voltages of 220kV and 242kV, equipped with a ±2×2.5% off-circuit tap-changer to accommodate normal system voltage fluctuations.

2. Flexible Capacity and Voltage Matching:

- Offers a wide range of standard capacities from 31.5 MVA to 240 MVA, meeting the requirements of power transmission and transformation projects of various scales.

- The low-voltage side primarily provides common industrial and distribution voltage levels such as 6.3kV, 6.6kV, 10.5kV, and 13.8kV, precisely matching end-user connection needs.

3. Optimized Electrical Performance:

- Employs the standard YNd11 vector group, ensuring good system compatibility and straightforward protection configuration.

- Short-circuit impedance is designed between 12% and 14%, achieving an optimal balance between limiting short-circuit currents and maintaining voltage stability.

- The no-load current is as low as 0.26%. Both no-load and load losses are systematically optimized, ensuring high operational energy efficiency.

Typical Applications

- Main transformers for 220kV regional substations and end-user substations.

- Main transformers for step-up substations in renewable energy projects such as wind farms and photovoltaic power plants.

- Main step-down transformers for large-scale industrial enterprises.

- Key nodes in urban power grids responsible for power transmission and distribution.

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