TDS Transformer Dryout System Photo

Transformer Dryout System (TDS®)

Dehydrate wet transformers without taking them out of service!

View Datasheet PDF #1802



The TDS® transformer dry-out system incorporates all the necessary features to allow a transformer to remain in-service while moisture from its insulation is effectively removed. The system is safe with several alarm features that shut the system off, isolating it from the transformer,
in the event of any abnormal signal. The TDS5-1 unit provides a non-intrusive, cost effective and convenient method of maintaining transformers in a dry condition. In addition, once the transformer is dried, the system can be retrofitted with Activated Alumina cartridges to reduce acidity in the transformer oil. This flexibility allows increased oil processing application compared to heat and vacuum systems.

The TDS® oil processing system is designed to allow a transformer under load to dry itself out. A quantity of four part number SD-1107 Superdri® cartridges are installed in the filter vessel, through which oil is processed at a rate of 5 gpm. The filtering system removes dissolved water from oil to less than 10 ppm, and includes 1 micron nominal particle removal capabilities. The process does not affect dissolved gas in oil, and does not remove oil oxidation inhibitors. The system is complete with all components necessary to monitor the mechanical and electrical operating conditions of the unit. The system includes components to purge air during start up and after filter changes.

The on-line dryout process is designed for safe, unattended, 24-hour operation. The system suction line is connected to the transformer bottom fill connection. The oil is then returned from the TDS® to a top connection valve. The number of cartridge changeouts required to dry the transformer insulation to an acceptable level and cartridge change-out intervals will vary according to moisture content and moisture transfer rate from the insulation to the oil. One set of Superdri cartridges will remove a minimum of 1.4 gallons of dissolved water from the oil. Periodic moisture readings, from both the inlet to and outlet from the system can be taken to determine the amount of moisture being removed and are also used to determine when cartridges should be changed.

TDS5-1 Standard unit, 120 vac, 1-ph, 60 Hz power requirement
746Y012 Moisture Sensor Option, 120 vac, 1-ph, 60 hz
SD-1107 Superdri® cartridge, 4 required per change-out (not included with unit)
LB-1107 Activated alumina cartridge for acid removal, 4 required per changeout

Companies that use the Velcon TDS® Transformer Dry-out System

Partial list - more than 200 units sold in the last ten years!  


Ameren Union Electric
Bonneville Power
Carolina Power & Light
Con Edison
Consumers Energy
CXY Chemicals
Delmarva Power & Light
Duke Energy
Energy Services New Zealand
Georgia Power
Gulf Power
Los Angeles Department of Water & Power
Metropolitan Edison
Mississippi Power
Occidental Chemical

Ontario Power Generation
Pennsylvania Power & Light
Portland General Electric
Potomac Electric Power Company
Progress Energy
Public Service Company of Oklahoma
San Diego Gas & Electric
Southern California Edison
Southern Illinois Power
Southern Mississippi Electric
Tri State G & T
US Army Corp or Engineers
US Dept of Energy WAPA
West Oregon Electric Coop