VACUUM OIL FILLING - DEGASSING - DEHYDRATING

TSI has been providing vacuum oil filling services to large power transformers since 1960. The equipment was designed and assembled by TSI's personnel to be self-sufficient and capable of performing in all voltage ranges, including test transformers rated at 1,500,000 volts.

This unique system electronically measures the amount of vacuum being drawn on the transformer tank and on the oil dehydration chamber. Once transformer vacuum has been maintained for the required amount of time, the oil filling procedure begins. The oil first goes through a five-micron particle filter, a heat exchanger to raise the oil temperature to the desired level, and then is sent into the vacuum degassing/dehydration chamber. Here, the hot oils surface area is greatly increased by special elements within the chamber, which allows the high vacuum being applied to the chamber to remove moisture and unwanted gasses. The oil then flows through a one-micron filter and is pumped into the transformer, which is still under high vacuum to assure additional dryness of the oil and internal transformer components. All piping, connections, and hoses are kept under positive pressure from the discharge side of the dehydration chamber through to the transformer tank oil hose connection to eliminate the possibility of moisture entry. TSI can also provide a cold trap for vacuum fills or for dry-outs under vacuum.

During the oil filling procedure, the incoming and outgoing oil is periodically monitored for moisture content and dielectric. On-site Power Factor tests can also be performed if requested in advance, as well as test for interfacial tension (IFT) and acidity.

The vacuum fill unit has an oil handling capacity, depending on the desired oil temperature, of up to 1800 GPH, and will process oil at values which meet or exceed all transformer manufacturing specifications (see reverse for chart).

The same equipment is also used to dehydrate and degas the oil in transformers that have been in service. In the case of moisture, oil and paper insulation can frequently become wet due to headspace leaks to the atmosphere. Cooling/heating cycles cause transformers to "breathe" through the leak, allowing moisture to enter the headspace and gradually be absorbed. TSI's hot oil dehydration equipment effectively removes all but traces of this dissolved water. Results are normally less than 10 ppm residual moisture in the oil, but can go lower if desired. A complete typewritten report is prepared and mailed to the customer showing vacuum readings, moisture results, and dielectrics by selected hours from the start of the process to completion.

Combustible gas caused by minor faults within the transformer, such as overheating or arcing at a loose connection, corona discharges, lightning, etc., can easily be removed by this equipment. Oil samples are taken after processing and are returned to our laboratory for Dissolved Gas-In-Oil Analysis. These results then serve as the benchmark for which future results are compared against to determine the internal condition of the transformer.

FIELD TESTS AND TEST METHODS

TYPICAL VALUES FIELD TESTS AND TEST METHODS

TYPICAL VALUES

DIELECTRIC STRENGTH (ASTMD877 & D1816*)

40-50kV MOISTURE CONTENT (DOBLE DOMINO 264)

<10ppm

VACUUM (ELECTRONIC GAUGE)

.20 - 1.0mm INTERFACIAL TENSION* (ASTMD2285)

**

NEUTRALIZATION NO.*(ASTMD974)

**

LABORATORY TESTS ANDTEST

METHODS

TYPICAL VALUES LABORATORY TESTS ANDTEST

METHODS

TYPICAL VALUES

MOISTURE CONTENT (ASTMD1533)

<15ppm DISSOLVED GAS-IN-OIL* (ASTMD3612)

<500ppm TCG

POWER FACTOR @ 100oC (ASTMD924)

<.40% @ 100oC PCB CONTENT (ASTMD4059)

**

* DENOTES OPTIONAL TESTS - TO BE PERFORMED AT CUSTOMER'S REQUEST, WITH PRIOR NOTICE

** THESE TEST VALUES AREDEPENDENT ON INITIAL OILCONDITIONS ANDWILL NOT CHANGE SIGNIFICANTLY AFTER TREATMENT

The following is a list of the equipment TSI uses for its vacuum oil filling and degassing/dehydration services:

VACUUM PUMPS: Leybold Heraeus 165 CFM Mechanical Pump, 710 CFM Blower. Capable of vacuum to less than 100 microns, absolute pressure.

HEAT: Provided by two oil fired boilers with heat exchanger providing over one million BTU's.

INTAKE AND DISCHARGE OIL FILTERS

EXPANDED SURFACE AREA VACUUM CHAMBER

TEMPERATURE GAUGES AND SAFETY CONTROLS FOR OIL LINES

OILFLOWMETER ON DISCHARGE LINE

ELECTRONIC VACUUM METER With probe hookups for transformer,vacuum pumps, and vacuum chamber.

OIL SAMPLE TAPS On intake and discharge oil lines.

ELECTRICAL POWER: Diesel engine powered 30 kW generator.

HIPOTRONICS DIELECTRIC TESTER Using Flat disk or VDE cell set at .04 gap, tests to 60 kV automatically.

DOBLE DOMINOTMMODEL 264 moisture analysis

ALL HOSES AND FITTINGS NECESSARY FOR VACUUM AND OIL LINE CONNECTIONS.