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138kV HV Transformer — 105/140/175 MVA

138kV High Voltage Power Transformer — 105/140/175 MVA

HV Power Transformer 40 MVA, 3-Phase
Reliable Power, Proven Performance

Engineered for high performance and reliability, the 138kV 105/140/175 MVA Power Transformer from Pennsylvania Transformer Technology delivers exceptional efficiency, rugged construction, and precise voltage regulation for demanding utility and renewable applications.  Assembled in the USA to ISO 9001 and IEEE standards, the power transformer combines proven durability with advanced design for maximum uptime & long-term value.

Pennsylvania Transformer Technology, LLC (PTT) presents the 138kV High Voltage Power Transformer, designed and assembled in Canonsburg, PA. Built to exceed ANSI and IEEE standards, this three-phase 138kV transformer delivers exceptional electrical performance, optimized loss characteristics, and dependable long-term operation for high-capacity grid and renewable applications such as utility solar interconnections. 

Key Specifications ​​ 138kV High Voltage Power Transformer

​MVA Ratings

Power Rating

  • 105/140/175 MVA (ONAN/ONAF/ONAF)        
Cooling System Options

Cooling System Method

  • ONAN / ONAF / ONAF — Oil Natural Air Natural for base rating and Oil Natural Air Forced for higher ratings.​ONAN / ONAF dual-stage forced oil-air cooling
Voltage Rating

Voltage Ratings

  • Primary Voltage: ​138 kV Y / 79.674 kV
  • Secondary Voltage: 34.5 kV Y / 19.919 kV
  • Tertiary Voltage:  13.8 kV Δ (Buried)
Impedance

Phases/Tap Range

  • Phases: 3
  • ±10 % in 16 steps of 1.25 % each (using RMV-II vacuum LTC)
138kV Power Transformer ​Performance Highlights
  • High Efficiency: Optimized magnetic design achieves 99.77 % efficiency at ½-load and 99.74 % at full load.
  • Precision Loss Testing: Conducted with Multi-Amp Canada calibrated systems with ±1.08 % load and ±0.30 % no-load error.
  • Flexible Voltage Regulation: On-load tap changer provides ±10 % voltage regulation in 16 equal steps.
  • Robust Mechanical Design: Heavy-duty tank and core with optimized cooling and high short-circuit strength.
  • Proven Insulation Integrity: Tested per ANSI C57.12.10 standards with 248 kV induced voltage & 650kV BIL ratings.  
138kV Transformer ​Applications
  • Utility and renewable generation (138kV solar interconnection)
  • High-voltage transmission and substation service
  • Industrial power distribution requiring high efficiency and voltage stability
138kV Power Transformer ​ Design and Construction Features
  • Load Tap Changer (LTC): Reinhausen RMV-II vacuum type for enhanced reliability and low maintenance.
  • Oil Preservation System: Conservator design maintains oil purity with Qualitrol or Messko monitoring fittings.
  • Cooling System: Dual ONAN/ONAF/ONAF operation with modular radiator banks and forced-air cooling fans.
  • Construction: High-grade steel core, porcelain bushings, corrosion-resistant tank, and control cabinet prewired for monitoring.  
Certifications and Compliance
  • ISO 9001:2015 Certified (Design and Manufacture of Power Transformers)
  • ANSI / IEEE Standards Compliance (C57.12.10)
  • NMSDC Certified Supplier  
Ask How PTT Can Deliver on Your Power Transformer Specifications