Specifications_For_The_Repair_of_Substation_Transformer_AC_21_(2).pdf
PDF 52 KB Posted
- Solicitation number
- IFB197195
- Issued by
- Santa Clara County, California
About this file
This is a Specifications document for the City of Palo Alto Utilities outlining the repair and refurbishment of a 15 MVA Allis Chalmers substation transformer equipped with a TLH-21 on-load tap changer (OLTC). The transformer, originally manufactured in 1967, requires replacement of its OLTC due to mechanical failures preventing proper tap changing, despite the core and coil remaining electrically sound. The scope of work includes comprehensive oil handling and processing, with approximately 4,348 gallons of main tank oil to be drained into a contractor-provided tanker for reuse and 760 gallons of OLTC tank oil to be drained into City-provided containers for disposal or replacement. Additional work includes replacement of radiator valves and gaskets, removal and replacement of the 60 kV SMD fuse holder, pressure testing of the main tank, resealing of all interfaces to eliminate oil migration, and execution of comprehensive pre- and post-work diagnostic testing. Pre-work testing shall include power factor testing on bushings and windings, transformer turn ratio (TTR) testing at all OLTC positions, excitation testing, winding resistance measurement, and dissolved gas analysis (DGA) with oil quality assessment. Post-work testing includes identical testing protocols plus SFRA (Sweep Frequency Response Analysis) analysis.
The contractor shall provide all labor, equipment, and materials required to complete the project, with the City responsible for de-energizing, disconnecting, isolating, and grounding the transformer prior to work commencement and disposing of any transformer oil not intended for reuse. The specifications emphasize that the selected contractor must demonstrate expertise in OLTC replacement, transformer oil processing, and high-voltage diagnostic testing. The project objective is to restore full mechanical functionality and dielectric reliability of the transformer system, prevent further degradation, and extend the operational service life of this critical distribution asset.
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Text version
Specifications for repair of Substation transformer AC 21
Replace the on-load tap changer (OLTC) on the Allis Chalmers 15MVA, 60KV-12470/7200V substation transformer. The OLTC is a TLH-21 from 1967. The unit is experiencing mechanical problems preventing the OLTC from changing positions. The transformer is energized and does not show signs of core and coil electrical malfunction. There is evidence of minor oil migration between the OLTC cabinet and the Main tank. There are two radiator valves leaking.
The contractor shall provide all labor, equipment and materials required to:
• Complete testing of the transformer prior to commencing any work
• Drain TLH-21 LTC tank into city provided containers for disposal. (760 gal)
• Drain main tank (4348 gal) into contractor provided tanker. Oil to be re-used.
• Replace the TLH-21 LTC with a certified re-manufactured component
• Re-seal barrier board and all pass-through studs to stop oil migration between LTC and Main tank
• Replace LTC tank door and hand hold gaskets
• Remove and replace the 60KV SMD fuse holder to accommodate removal of the radiators.
• Replace valves and gaskets on all six radiators
• Pressure test main tank and replace gaskets or seals disturbed during work.
• Process Main tank oil and vacuum fill transformer
• Fill LTC tank with new oil (760 gal)
• Complete testing of the transformer after completion of the work
The City will be responsible for de-energizing, disconnecting, isolating and grounding the transformer as required to establish a safe work area. The city will dispose of any transformer oil not to be re-used.
Preliminary tests of transformer condition.
• Power Factor the primary bushings
• Power Factor the primary and secondary windings
• TTR all positions of the OLTC (as found ONLY on the NLTC)
• Excitation
• Winding resistance
• DGA and oil quality testing includes moisture content, dielectric breakdown, and power factor @ 100°C (main tank and OLTC)
Post work tests to be performed:
• Power Factor testing on the bushings
• Power Factor testing on the windings
• TTR - all positions
• Excitation
• Winding resistance
• SFRA
• DGA and oil quality testing includes moisture content, dielectric breakdown, and power factor @ 100°C (main tank and LTC)
File details come from the government source that posted it. Updated .