RFI_Responses_7_April_2015.docx

7 April 2015 Request for Information Responses

1. Drain oil from T1 transformer located at Nellis AFB substation. The contractor is responsible for storage of the oil.

-We assume the transformer main oil compartment and load tap changer (LTC) compartments are presently filled with oil. However is the transformer currently energized? If it is not energized, is the load tap changer (LTC) compartment presently filled with oil? At the site visit will we be able to inspect the LTC oil compartment with the oil compartment doors opened if needed?

Response: Currently the transformer is de-energized and the LTC compartment is filled with oil. Unfortunately do to the design of the transformer we are not able to inspect the LTC until the oil is removed so we will not be able to examine the LTC at the site visit.

3. Perform internal inspections on the transformer to include oil containment barrier walls, seals, contacts and tap changer components.

-The 'internal inspection' required above, is this just for the LTC oil compartment section or the main tank and related internal components as well?

Response: The inspection will cover the LTC oil compartment, main tank and related internal components.

4. Clean inside transformer oil tank reservoir.

-By 'oil tank reservoir', do you mean the oil preservation conservator? We assume this transformer is a conservator type or has a conservator oil preservation system as opposed to a nitrogen blanketed sealed tank preservation system? Can you provide pictures of the transformer prior to the site visit?

Response: The transformer is a nitrogen blank style system.

5. Remove reversing switch, diverters, and other components as required to allow for removal of the tap head assembly.

-Will any of these parts (other than the tap heads) intended to be reused?

Response: All functional parts will be reused

6. Provide and install three replacement tap head assembly with contacts.

-In order to provide costs and plan to install the proper LTC tap heads, we will need the model of the LTC mechanism. Usually the LTC will have a nameplate denoting the type of switch, model, and rating information either affixed the exterior of the LTC tank or affixed to the interior side of the air compartment door. Can you provide a picture of the nameplate or a picture of the inside of the air compartment of the LTC?

-Also, this information is sometimes annotated on the main transformer nameplate or outline drawing of the transformer. Can we have electronic copies of both drawings prior to the site visit?

-In regards to 'head assembly with contacts', in regards to the contacts, are you only asking for selector stationary contacts? Or is scope to replace all the LTC contacts, including the stationary and moving selector contacts, all reversing stationary and moving contacts, all diverter arcing contacts?

Response: We are looking to replace all the of LTC contacts for the three tap heads that are being replaced and any damaged components associated with the LTC that are extremely worn, damaged or potentially causing the oil leak between the primary and secondary barriers. Without being able to investigate inside of the transformer we are utilizing past experiences to determine what may be causing the current leak and looking to replace any damaged components of the LTC while the tank is drained and the compartments are accessible.

7. Provide seal replacement kit and install all penetration seals for components and barrier wall penetrations.

-We assume this pertains only to the LTC tap heads and the gasket seal to the tank wall and outside LTC oil compartment door seals? Or does it pertain to the main transformer as well?

Response: All seals/gaskets that are utilized to secure penetrations through the tank wall and the LTC need to be replaced.

Below are some photos of the current transformer:

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