Core type power transformers up to 400MVA 345kV Shortest lead time in the industry Shell type power transformers up to 1400MVA 500kV The most reliable transformers made right here in the USA

MANUFACTURING

Our value proposition is to provide the most reliable transformer that’s shipped and installed in a timely and flawless manner to the site and monitored and serviced to last for more than 60 years.

A reliable transformer requires a robust design and equally important is its flawless execution.  Our flawless execution of a robust design is based on the following Manufacturing Pyramid. At the core lies people, supported by modern equipment and factory, a proven process and flawless shipping and installation

  • Trained certified technicians under experienced supervision
  • Modern, clean factory & state of the art equipment
  • Error-free manufacturing and assembly of
    • Core
    • Coils
    • Tank
    • Assembly (internal & external)
  • Accurate and error-free testing
  • Flawless Shipping and installation

People

As mentioned before, the core of flawless execution pyramid is people -Trained and Certified Technicians.

We have 3 pies in our people chart;

  • Trained, certified technicians.
  • Professional overseeing of these technicians.
  • A team and a plan that ensures that tools and materials are in place in a timely manner.

Trained & Certified Technicians

Professional Overseeing

Trained Technicians are essential and their training must be continuous & up to date.
But even more important, is their guidance. This is what we call “overseeing”. Experienced supervisors are continuously analyzing the finished work, the tasks in process from all angles to make sure that everything makes sense, everything fits together. And without tools and materials nothing is going to move forward. A team within VTC-GTC is dedicated to ensure that process doesn’t stop because tools and materials not showing up on time.

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Core

Coil Winding

Coil Sizing

Insulation

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VPD

HOS

In construction of power transformers, depending on the voltage class, it is desirable to suppress the water content of cellulosic-based materials to <0.5 % and even as low as 0.1 % (by weight) prior to shipment. Cellulosic Kraft materials such as high density pressboard, papers, tapes, crepe tubes and spacers are used in the paper/oil insulation system of the transformer. These are used to support windings and leads as well as to maintain dielectric clearances, these usually contain 8 – 10% of moisture by weight at ambient temperature. This is dangerous to the health of the transformer because it reduces the electric strength, resistivity and accelerates deterioration of solid insulation. Therefore, it is required to remove moisture from insulation to maintain its insulating properties. Conventional drying has not remained efficient and effective in terms of energy savings, cost of operation and achieving process parameter.

 

Process Summary

Complete Dry out of the core and coil assembly begin by placing the entire assembly inside vapor phase drying chamber. Vapor Phase Drying (VPD) also applies vacuum but the method of heating is not through air. In this method, the carrier of heat is Vapor of a low viscosity solvent like kerosene with a higher flash point. Vapor is heated in an evaporator by use of electric heaters and are passed over the core and coil assembly placed inside for drying. The solvent vapor condenses when encountering the lower temperature job.

The condensed kerosene is collected and subjected to many rounds of heating and evaporation. The job temperature rises and evaporated water is pumped off to attain thorough drying. Vacuum maintained during the process is very low (as low as < 0.5 Torr).

Dew point reading dictates end of cycle and thus unit is ready for oil spray process. Unit is now sprayed with transformer oil within the chamber to cover the pores of cellulosic material (insulation) to inhibit moisture absorption.

At this point the unit is taken out from vapor phase vacuum chamber and proceeds to a process called servicing. Unit is retightened to compensate any shrinkage. With minimum exposure time unit is tanked immediately and covered, vacuum is applied prior to oil filling for final impregnation, after appropriate “under vacuum” time, testing of transformer begins in accordance to customer specification and standards.

In summary, the use of vacuum allows for drying of the components without the need of high heat that would be detrimental to the insulation material.

Each of our factories are equipped with VPD ovens.  We have three independent 430.5 sqft (13345 cubic foot) VPD ovens for the drying of transformer active parts and accessories at our large and extra-large power transformer manufacturing plant in Rincon, GA.  Each oven is PLC operated to allow for precise temperature, vacuum and time control and allows for adjustable Isostatic pressing of transformer winding to ensure proper calibration and sizing of the coils.

If a transformer is too large for VPD, then Hot Oil Spray (HOS) method is used for drying. In this method, transformer is placed under vacuum, and sprayed with heated transformer oil to drive the moisture away. HOS is continued until the desired moisture levels are achieved.

This is a typical flow of assembly at GT, Rincon plant. Processes at all other plants are essentially the same in principle but may vary depending on the size of the transformers.

There are many processes in the assembly with checks and balances. We have boiled them down to 11 major hold points “HP” where the process will not move forward without approvals. And then there are 2 major control points where team leader will analyze, review the finished work from different angles to make sure everything makes sense, and we’re on the right track. A traveling binder will document all the inspection work for any kind of root cause analysis for later use.

Tanks

Control Box

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Cranes & Air Cushion Systems

Environmental Control

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