Scott Transformer

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Product Overview

Scott Transformer

High-voltage rated voltage	10kV / 35kV / 110kV; customizable
Low-voltage rated voltage	Customized for traction / arc furnace loads; typical 2 x 27.5kV
Rated capacity	1MVA - 120MVA
Power Supply Mode	Three-phase to two-phase or two-phase to three-phase power conversion
Frequency	50Hz; 60Hz customizable for overseas projects
Cooling Type	Oil-immersed: ONAN / ONAF / OFAF; dry-type: AN / AF

Technical Specifications

Parameter	Value	Parameter	Value
High-voltage rated voltage	10kV / 35kV / 110kV; customizable	Low-voltage rated voltage	Customized for traction / arc furnace loads; typical 2 x 27.5kV
Rated capacity	1MVA – 120MVA	Power Supply Mode	Three-phase to two-phase or two-phase to three-phase power conversion
Frequency	50Hz; 60Hz customizable for overseas projects	Cooling Type	Oil-immersed: ONAN / ONAF / OFAF; dry-type: AN / AF
Transformer Type	Scott Connection Transformer	Connection Type	Scott connection with Main Transformer and Teaser Transformer
Phase Conversion	Three-phase to two-phase and two-phase to three-phase bidirectional conversion	Two-phase Output	Equal voltage magnitude with 90° electrical phase shift
Vector Group	Scott connection, combined Main + Teaser transformer unit	Installation	Indoor / Outdoor
Insulation Level	Compliant with IEC 60076 and GB 1094 series standards	Ambient Conditions	-40°C to +40°C; high-altitude, coastal salt-spray and extreme-cold versions available
Typical Model	25MVA, 110kV / 2 x 27.5kV oil-immersed Scott traction transformer	Typical Rated Capacity	25MVA
Typical HV Three-phase Voltage	110kV	Typical LV Two-phase Voltage	2 x 27.5kV
Typical Phase Shift	90° between the two-phase outputs	Typical Cooling Arrangement	ONAF oil-immersed forced-air cooling
Anti-corrosion Grade	C3, C4, C5, CX-H	Typical Installation	Outdoor traction substation installation
Connection Characteristic	Standard Scott connection for balanced three-phase to two-phase conversion	Negative-sequence Mitigation	Designed to reduce negative-sequence current injected into the three-phase grid
Partial Discharge Level	<100pC at 1.5 x rated voltage for oil-immersed type; <=10pC at 1.1 x rated voltage for dry-type	Noise Level	<=68dB(A) at 1m; low-noise version available
Short-circuit Withstand	Designed according to IEC 60076-5 with multi-physics structural reinforcement	Short-circuit Test	Performed only by specialized accredited third-party testing institutions
Thermal Performance	Temperature rise compliant with IEC / GB standards	Thermal Margin	Sufficient thermal margin reserved for unbalanced two-phase loads
Design Life	>=30 years under normal operating conditions	Insulation Medium	Mineral oil or high-fire-point ester oil for oil-immersed type; dry-type epoxy encapsulation
Oil-free Option	Dry-type epoxy encapsulation with no insulating oil	Fire Safety	Dry-type configuration without oil-related fire or explosion risk
Carbon Footprint	LCA life-cycle assessment documentation available upon request	ESG Support	LCA documentation available to support customer ESG reporting
Core Material	High-permeability low-loss grain-oriented silicon steel	Core Structure	Independent core structures for Main Transformer and Teaser Transformer
Core Joint Control	Strict joint control to reduce no-load loss and noise	Core Clamping	Controlled clamping force for mechanical stability and reduced vibration
Core Coating	Insulating anti-corrosion coating	Winding Structure	Main winding and Teaser winding with turns precisely matched according to Scott theory
Winding Ratio	Winding turns precisely matched according to Scott connection theory	Conductor Transposition	Transposed conductors to reduce additional eddy losses under unbalanced loads
Winding Insulation	High-strength insulation structure designed for frequent two-phase load fluctuations	Oil-immersed Winding Process	Multi-stage vacuum drying and vacuum oil filling
Dry-type Winding Process	Epoxy fibreglass vacuum-impregnated encapsulation	Partial Discharge Control	Turn and layer insulation redundancy with strict partial-discharge control
Oil Tank	Steel tank with magnetic shielding to reduce tank stray loss	Tank Integrity	100% weld inspection and positive / negative pressure tightness testing
Oil Tank Corrosion Protection	C3, C4, C5, CX-H	Cooling Selection	ONAN / ONAF / OFAF for oil-immersed type; AN / AF for dry-type
Bushings	Available as standard auxiliary equipment	Tap-changer	Off-circuit tap changer or OLTC optional
Pressure Relief Device	Available for oil-immersed configuration	Buchholz Relay	Optional protection accessory for oil-immersed type
Oil Level Indicator	Available for oil-immersed configuration	Winding Temperature Sensor	PT100 winding temperature sensor
DGA Monitoring	Dissolved gas analysis online monitoring available as an option	Special Options	Buchholz protection / winding temperature measurement / DGA online monitoring
Electromagnetic Design	3D FEM simulation with Scott connection magnetic circuit modeling	Ampere-turn Balance	Main and Teaser winding ampere-turn balance verification
Unbalanced Load Analysis	Stray-loss calculation under unbalanced two-phase load	Negative-sequence Analysis	Evaluation of negative-sequence current on the three-phase side
Mechanical / Seismic Design	ANSYS structural simulation for short-circuit electrodynamic force and structural strength	Seismic Qualification	IEEE 693 compliance available for high-seismic-intensity substations
Short-circuit Simulation	Transient electromagnetic-field simulation for three-phase-side and two-phase-side short-circuit conditions	Winding Force Analysis	Dynamic electrodynamic force calculation and winding structural verification
Insulation Coordination	Electric-field simulation for main and longitudinal insulation	Impulse Withstand	Lightning impulse and switching impulse withstand verification
Thermal-flow Simulation	CFD oil-flow / air-convection simulation	Hot-spot Analysis	Hot-spot temperature prediction under steady-state and unbalanced two-phase loads
Capacity Ratio Optimization	Simulation-based optimization of Main Transformer and Teaser Transformer capacity ratio	Stray-loss Optimization	Reduction of stray heating caused by unbalanced loads
Applicable Standards	IEC 60076-1 / IEC 60076-2 / IEC 60076-3 / IEC 60076-5	China Standards	GB 1094 series and GB/T 6451
North America Standard	IEEE C57.12.00 optional for export projects	Seismic Standard	IEEE 693 optional for high-seismic-intensity substations
Environmental Compliance	RoHS / REACH hazardous-substance control	PCB Requirement	PCB-free insulating liquid requirement according to EPA 40 CFR Part 761
Material Compliance	Key components and insulation materials comply with IEC / GB requirements	Material Traceability	Full material traceability throughout the supply chain
Factory Acceptance Test	Routine and type tests including ratio measurement, vector group verification, DC resistance, loss, partial discharge and dielectric withstand	FAT Short-circuit Scope	Short-circuit test excluded from FAT scope
Witness Testing	Client or third-party witnessed testing available	Third-party Short-circuit Testing	Specialized accredited third-party laboratory required
Site Service	Installation guidance, tanking supervision, core lifting if required and pre-commissioning inspection	Commissioning Support	Technical support for commissioning
Warranty	Comprehensive product warranty	Extended Service	Extended service agreement optional
Spare Parts Supply	Minimum 25-year spare-parts supply for key components	Training	On-site or remote operation and maintenance training
Training Scope	Scott connection principle, unbalanced load characteristics, negative-sequence impact and O&M requirements	Quality Management	ISO 9001 / ISO 14001 / ISO 45001
Customization Capability	Oil-immersed / dry-type design with flexible capacity and voltage combinations	Special Environment Options	High-altitude, salt-spray anti-corrosion, low-noise and online monitoring options
Typical Application	Electrified railway traction substations	Railway Function	Three-phase to two-phase conversion for catenary power supply and negative-sequence reduction
Metallurgical Application	Two-phase AC electric arc furnace power supply	Industrial Load Application	High-power two-phase industrial loads
System Retrofit Application	Legacy two-phase power system renovation	Conversion Function	Bidirectional two-phase to three-phase and three-phase to two-phase conversion
Special Test Application	Two-phase orthogonal power test bench	Project Experience	Railway traction and metallurgical arc furnace Scott transformer projects
Export Frequency	60Hz versions available for overseas EPC projects	Technical Documentation	Simulation reports, type-test reports, material certificates and traceability documents
Negative-sequence Report	Negative-sequence calculation report available	Technical Support	Early coordination with design institutes for system-level technical evaluation

Protection & Accessories

Reliable Protection System and Flexible Accessories

Our Pad Mounted Transformers are equipped with reliable protection devices and accessories to ensure safe operation in underground distribution systems and utility applications.

Standard Accessories

HV/LV Bushings

Reliable medium voltage connection with excellent insulation performance.

Oil Level Gauge

Easy monitoring of insulating oil level for maintenance.

Pressure Relief Device

Improves transformer safety under abnormal conditions.

Drain Valve

Convenient oil draining and maintenance operation.

Tap Changer

Off-circuit Tap Changer (OCTC), ±2 × 2.5%

Nameplate

Provides complete transformer rating and technical information.

Optional Accessories

Temperature Indicator

Monitors transformer operating temperature for reliability.

Remote Monitoring System

Supports smart grid and remote transformer condition monitoring.

Surge Arrester

Protects pad mounted transformers against lightning and voltage surges.

Key Features of Transformers

Key Benefits:

Enhanced operator and public safety
No exposed high-voltage components
Suitable for underground distribution systems
Reliable operation in outdoor environments

Key Benefits:

Weather-resistant construction
Corrosion-resistant surface treatment
Secure locking compartment
Suitable for public and utility applications

Key Benefits:

Space-saving installation
Low-profile outdoor design
Easy inspection and maintenance
Ideal alternative to overhead distribution systems

Available Configurations:

Loop feed distribution system
Radial feed distribution system
Dead-front cable connection
Customized MV and LV connection arrangements

Available protection and accessories include:

High voltage fuses
Current limiting fuses
Load break switches
Surge arresters
Pressure relief devices
Temperature monitoring systems

These protection solutions help ensure safe operation under different load and fault conditions.

Key Benefits:

Low no-load losses
High energy efficiency
Excellent thermal performance
Long operational lifetime

Manufacturing & Testing

Strict Quality Control and Transformer Testing

Every Pad Mounted Transformer undergoes comprehensive testing to ensure high reliability, safety and long service life according to international standards.

Routine Tests

Transformer Ratio Test

Ensures accurate voltage transformation performance.

Winding Resistance Test

Verifies winding quality and electrical performance.

No-Load Loss Test

Checks transformer core efficiency and energy performance.

No-Load Loss Test

Confirms transformer rated efficiency under operating conditions.

Impedance Test

Ensures correct electrical characteristics and system compatibility.

Dielectric Test

Verifies insulation strength and operational safety.

Special Tests

Temperature Rise Test

Validates thermal performance and cooling capability.

Lightning Impulse Test

Tests insulation capability against surge conditions.

Partial Discharge Test

Ensures insulation quality and long-term reliability.

Everything We Do Is At A High Standard

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WHAT WE DO

CTSS Transformer Applications and Solutions

We design and manufacture liquid-filled power transformers and distribution transformers for a wide range of applications, including solar power, data centers, industrial facilities, and utility systems. With experienced engineers and advanced manufacturing capabilities, we provide customized transformer solutions and complex winding designs to meet the specific electrical and performance requirements of each project.