66kV Oil-Immersed NLTC Power Transformer

66kV Oil-Immersed 3-Phase 2-Winding NLTC Transformer.

Compact, cost-effective solution for 66kV distribution and industrial grids.

Rated 3.15 to 63 MVA, HV 63/66/69kV with ±5% or ±2×2.5% taps.

Features YNd11 vector group, low no-load current (0.29%), and robust off-circuit design for minimal maintenance.

Product Overview

This series represents a compact and cost-effective two-winding power transformer designed for 66kV medium-high voltage distribution networks.

Suitable for renewable energy plants, industrial parks, and regional grids, it serves as an economical and reliable solution for connecting high-voltage grids directly to end-user equipment.

66kV-substation-wind-solar-power-transformerjpg

66kV oil-immersed power transformer installed in a renewable energy substation with wind turbines.

Technical Specifications

Rated capacity (kVA)	Rated voltage and tapping range			Vector group	No Load Current (%)	Short-circuit impedance (%)	No load Losses (kW)(11)	On load Losses (kW)(11)
Rated capacity (kVA)	HV	Tapping range	LV	Vector group	No Load Current (%)	Short-circuit impedance (%)	No load Losses (kW)(11)	On load Losses (kW)(11)
3150	63 66 69	±5	6.3 6.6 10.5	YNd11	0.7	8	22	20.7
4000					0.64		2.6	24.6
5000					0.54		3.1	27.6
6300		±2×2.5			0.48	9	4	30.8
8000					0.48		4.9	36.5
10000					0.45		5.8	43
12500					0.45		6.8	51.1
16000					0.42		8.3	62.8
20000					0.42		9.7	76.1
25000					0.38		11.4	90
31500					0.35		13.5	108
40000					0.35		16.2	126.9
50000					0.32		194	150.3
63000					0.29		22.9	178.2

66kV-transformer-internal-winding-structure-3djpg

3D cross-section of 66kV transformer showing copper windings and NLTC tap changer.

Core Advantages

Extensive Grid Compatibility: HV side supports 63kV, 66kV, and 69kV, equipped with ±5% or ±2×2.5% off-circuit taps. Perfectly adapts to varying regional grid standards and voltage deviations.
Flexible Capacity & Low-Voltage Options: Ranges from 3.15 to 63 MVA. LV side offers standard 6.3kV, 6.6kV, and 10.5kV options, matching various end-user equipment interfaces without extra adapters.
Optimized Efficiency & Protection: Standard YNd11 vector group. Short-circuit impedance is tiered (8% or 9%) to limit fault currents and control voltage drop. Low no-load current (0.29%) ensures long-term energy savings.
Built for Low Maintenance: The off-circuit tap-changing design provides a simple, robust structure. Highly reliable with minimal maintenance, perfectly suited for stable operating environments.

Typical Applications

66kV grid-connection step-up transformers for renewable energy projects (wind farms and PV plants).
Main step-down substations (66kV) for industrial parks, mining, and large industrial enterprises.
Hub substations in local power grids connecting high-voltage transmission lines to distribution networks.
Dedicated power supply substations for urban rail transit and large-scale infrastructure.

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