Transformer Testing Services
Industrial Tests, Inc. offers complete testing, maintenance, and repair services to electrical substation and distribution transformers and load tap changers.
- Transformer oil testing and analysis on samples drawn by customers or by Industrial Tests, Inc. technicians.
Sampling and visual inspection.
Transformer repairs and re-gasketing.
Transformer oil re-refining, degassing, and dehydrating.
Assembly and vacuum oil filling of new transformers.
- Testing: Doble Power Factor, Dielectric Absorption, TTR, Winding Resistance, etc.
- Internal inspection and field repairs.
- Cleaning and on-site painting.
Transformer and Tap Changer reconditioning.
- Load Tap Changer Retrofits.
- Protective Relay and LTC control upgrades
- Bushing replacements.
Oil Cooler, Pump, Fan, and Radiator Change out.
- Replacement of guages and peripheral equipment.
Liquid Filled Transformers:
- Dissipation/Power Factor tests of the high, low, and tertiary voltage windings (CH, CL, and CHL).
- Transformer turns-ratio test (TTR) on all no-load tap positions.
- Excitation current test on the high side of the transformer.
- Core ground resistance test, if core ground is available.
- Dielectric absorption tests to include, high-to-ground, low-to-ground, high-to-low side tests will be made over a ten-minute period.
- Polarization Index will be calculated and temperature compensated.
- Winding resistance tests on both the high and low sides of the transformer using a transformer micro-ohmmeter.
The surface of the bushings will be thoroughly cleaned before beginning the test.
Solid bushings will be tested using the hot collar method.
On Liquid Filled Condenser Type Bushings (typically rated above 15kV) a Dissipation Power Factor test will be made at the bushing test tap, Doble test C1 and C2.
Oil Handling Standards
The following items apply to most all processing procedures. These standards are documented by Industrial Tests, Inc. Standard Operating Procedures.
- All equipment shall be grounded to the substation ground prior to the start of any work.
- A safety briefing shall take place.
- Hoses shall be properly bonded with a solidly connected ground.
- Any tank or tankers to be used are to be inspected and certified as clean prior to their use. Normally, the tankers are to be steam cleaned and certified clean by the supplier.
- Ancillary devices such as fault pressure relays or monitoring devices may require removal and blanking off or closing valves if not rated for full vacuum.
- All de-energized work shall be performed with the primary and secondary connections grounded with proper Lock-Out-Tag-Out (LOTO) procedures.
- Sign-off sheets for addressing items of completion such as being sure the bottom valves are closed and not leaking.
- The level on the transformer is to be confirmed.
- The transformer should be evaluated for leaks including the integrity of gaskets prior to and after processing.
- Record number and description of passes of oil reclamation.
- Record process detail such as temperature and flow rate.
Restoring service involves several steps to be observed by both Industrial Tests, Inc. and the owner. These steps are first dictated by the guidelines presented in the OEM service manuals provided by the manufacturer and are primarily for units that have been drained to the point that the core assembly has been exposed.
In the event that these OEM guidelines are not available through the owner or through Industrial Tests, Inc. then, at a minimum, the general IEEE guidelines according to PC57.93D14 shall be employed.
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