The Bureau of Reclamation (BOR) is a provider of wholesale water and hydroelectric power in the U.S. charged with distributing water to the 17 western states, and is best known for constructing dams, power plants, and canals. The BOR maintains a series of manuals called the Facilities Instructions, Standards, & Techniques (FIST), which pertain to the operation and maintenance of hydroelectric equipment, and contain must-know requirements for manufacturers.
FIST 3-30 is a BOR manual specific to transformer maintenance testing intended to guide power plant personnel in maintenance, diagnostics, and testing of transformers and associated equipment. FIST 3-30 details the necessary tests for dry type and liquid-immersed type transformers, which include the following:
- Infrared Imaging
- Identifies hot points, leaks and structural damage via thermal imaging cameras.
- Winding Resistance Testing
- Measure applied DC voltage and current, checking for loose connections, broken strands and high contact resistance in tap chargers
- Transformer Turn Ratio & Polarity Testing
- Verifies the operating principle of a power transformer, identifying shorted turns and open-circuited conditions and measuring ratio variations to ensure they fall within 0.5% of nameplate markings.
- Power Factor / Tan Delta / Doble Testing
- Power factor testing, also known as Tan Delta or Doble testing, measures capacitance and dissipation to determine the condtion of insulation in bushings or between windings and whether impurities like moisture or dirt are comprimising the insulation.
- Insulation Resistance and Ground Testing
- Determines the integrity of windings and cables in transformers, checking for insulation resistance deterioration due to temperature fluctuations, vibration, dirt, mechanical damage, oil, corrosive vapors, moisture from processes, and weather.
- Partial Discharge Tests
- Partial discharges, or corona, are small electrical sparks found within the insulation of electrical systems, and are caused by electrical breakdowns and discontinuities. A partial discharge test looks for insulation failure due to partial discharges.
- Short Circuit Impedance Testing
- A short-circuit impedance test will survey a coil for how loose or high-resistance its connection is, and indicates if the core and coils have been shifted by either mechanical or electrical damage.
- De-energization and Demagnetization
- By de-energizing and demagnetizing the core of power transformers, an operator eliminates erroneous diagnostics, inrush current at start-up, inaccurate measurements, and incorrect operation of protective relays.
- Motor Load Testing
- Ensures motor reliability, verifies performance, assesses system compatibility, identify faults, and validates repairs in motors. This ensures a motor does not overheat and performs at ideal capacity.