Adobe Creek Transformer-21; 15 MVA LTC Replacement & Radiator Flange Repair/Regasket

The City is soliciting proposals from qualified and experienced vendors to perform the repair and refurbishment of a 15 MVA Allis Chalmers substation transformer equipped with a TLH‑21 on‑load tap changer (OLTC). The existing 1967 TLH‑21 OLTC is exhibiting mechanical failures that prevent proper tap changing, although initial assessments indicate that the transformer’s core and coil remain electrically sound. Additional observed deficiencies include minor oil migration between the OLTC cabinet and main tank, as well as two leaking radiator valves.

The selected contractor will be responsible for the complete replacement of the TLH‑21 OLTC with a certified remanufactured unit, full oil handling and processing for both the OLTC and main transformer tanks, and resealing of all interfaces to eliminate oil transfer. Approximately 4,348 gallons of oil will be drained from the main tank into a contractor‑provided holding tanker for later reuse, while the OLTC tank oil (approximately 760 gallons) will be drained into City‑provided containers and replaced with new transformer‑grade oil if necessary based on testing and condition. The scope also includes replacement of radiator valves and gaskets, removal and replacement of the 60 kV SMD fuse holder, pressure testing of the main tank, and execution of all required pre‑ and post‑work diagnostic testing, including power factor testing, TTR, excitation, winding resistance, SFRA, DGA, and oil quality analysis. The City of Palo Alto Utilities will dispose of any transformer oil that is not intended for reuse.

The objective of this project is to restore full mechanical functionality and dielectric reliability of the transformer and its OLTC system, prevent further degradation, and extend the operational service life of this critical distribution asset. Vendors with demonstrated expertise in OLTC replacement, transformer oil processing, and high‑voltage diagnostic testing are encouraged to submit proposals in accordance with this IFB.