Transformer Repair, Rebuild, Refurbish and Upgrades
Built and Tested To
IEEE C57 12.01
and IEEE C57 12.91
Federal Pacific announces that the Bristol Transformer Plant is now ready to refurbish, repair and upgrade medium-voltage ventilated dry transformers from 112.5 KVA through 3750 KVA with HV ratings @ 5, 15, 25, and 35 kV having BIL ratings of 30 kV – 150 kV.
Large KVA 600V transformers in the range of 300-1500KVA are also economical to repair.
When the transformer inside your facility:
• Has failed.
• Requires higher efficiency
• Requires an increased KVA output
• Requires new high voltage from 4160 to 13800 or similar
• Needs a back-up core & coil
• Is a Liquid or PCB Filled Transformer
Then, Federal Pacific will have your answer.
To repair, rebuild or upgrade your existing dry-type transformer, Federal Pacific will need the basic rating information contained on the transformer’s nameplate that will be similar to the nameplate shown in Figure 1.
A repaired, refurbished or upgraded transformer is not subject to the DOE transformer efficiency guidelines that went into effect for Low Voltage on January 1, 2007 and the DOE efficiency Medium Voltage guidelines that will go into effect on January 1, 2010.
When a Transformer Has Failed
Critical data needed are emboldened on the sample nameplate in Figure 1. Contact Federal Pacific to obtain a RMA for sending the Transformer to the Bristol factory for repair.
Federal Pacific will offer recommendations with estimated repair costs and turnaround times, usually within 24 hours from receiving your information.
Upgrade – Efficiency
Also, it may be possible, while keeping the original core, to design the repaired transformer to have lower core losses than the original transformer.
Upgrade – KVA
Historically, one of the strong incentives for repairing a transformer is to increase the KVA power output of the unit. With today’s high temperature, 220° C insulation materials, and better knowledge of duct spacing and coil construction Federal Pacific can provide an increased KVA rating or a rewound transformer with a longer life expectancy than the original design. Sometimes this increased KVA output will have to be achieved by increasing the average winding temperature rise or by substituting copper conductor for aluminum.
Upgrade – Voltage (4160 ➝13,800)
In some cases the utility plans to increase the service voltage to a facility, typically from 4160 volts to 13,800 volts. In this situation the 4160 volt transformer has to be replaced or converted to the higher voltage, say 13,800 volts. Or perhaps the closing of a plant in another location has left the customer with an unusable transformer that has the wrong voltage. Federal Pacific in most cases can rebuild the existing transformer with the required higher voltage ratings and higher BIL without having to reduce the KVA output.
Wherever possible, Federal Pacific will work toward providing increased KVA, increased Efficiency, and upgraded Voltage Rating during the repair of the defective transformer.
Core and Coil Back-Up
For critical loads being served by a medium-voltage dry-type transformer in your facility, you can have Federal Pacific build a “duplicate” back-up core and coil that can quickly replace the present core and coil, should it fail.
Liquid Filled or PCB Replacement
In Figure 2 a Unit Substation Dry-Type transformer replacing a PCB liquid-filled transformer is illustrated. To accommodate the tight spacing between the previously installed HV Switch and LV Switchgear, this dry-type transformer has a HV-LV orientation that is 90° from the normal arrangement. Using the concepts in this illustration, Federal Pacific can replace your present liquid-filled transformer with a ventilated dry-type transformer having a higher temperature rated insulation system that contains no liquid and does not require the EPA Spill Prevention Control Countermeasures (SPCC) plan.
Figure 3 – Failed Transformer
Figure 5 – Dissasembled Failed Transformer
Figure 7 – Rectangular Layer-Type Winding
Figure 3 illustrates how a failed transformer appears when it first arrives at the Federal Pacific Bristol plant. Figure 4 shows the electrical testing performed on a failed unit to determine its condition.
Figure 5 shows the transformer after is has been completely disassembled.
Figures 6 and 7 provide examples of Federal Pacific’s ability to wind all types of windings for coil replacements.
If the old core is used, it is cleaned and painted to prevent corrosion. When a new step-lap mitre core replacement is used, the entire core and coil assembly will be dipped in a high-quality electrical varnish to prevent corrosion. After the new windings have been completed, they are placed on the core and the top yokes are again put in place, as shown in Figure 10.
Figure 4 – Incoming Electrical Testing
Figure 6 – Round Continuous Disc Winding
Figure 8 – State-of-the-Art Georg Core Cutter
If the customer wants an Efficiency Upgrade, Federal Pacific can cut a new step-lap mitre core utilizing the Georg core cutter, show in Figure 8, to give a modern step lap mitred core, shown in Figure 9.
Figure 9 – Step-Lap Mitre Core Laminations
Figure 11 – New Core and Coil
Figure 12 – Rebuilt Transformer
If the old core is used, it is coated with high temperature sealant to prevent corrosion. When a new step-lap mitre core replacement is used, the entire core and coil assembly will be dipped in a high-quality electrical varnish to prevent corrosion. After the new windings have been completed, they are placed on the core and the top yokes are again put in place, as shown in Figure 10.
At the end of this process the customer will receive a reconditioned transformer or a completely new core and coil, depending on what has been ordered, as shown in Figures 11 and Figure 12.