Department of veterans affairs vha master specifications

MEDIUM-VOLTAGE TERMINATIONS

1. 
   Terminate the medium voltage cables in the primary compartment with loadbreak premolded rubber elbow connectors, suitable for submersible applications. Elbow connectors shall have a minimum of 0.125 in [3 mm] semi-conductive shield material covering the housing. The separable connector system shall include the loadbreak elbow, the bushing insert, and the bushing well. Separable connectors shall comply with the requirements of IEEE 386, and shall be interchangeable between suppliers. Loadbreak elbow and bushing insert shall be from the same manufacturer. Allow sufficient slack in medium-voltage cable, ground, and drain wires to permit elbow connectors to be moved to their respective parking stands. Elbow connectors shall be rated as follows:
   
   1. 
      Voltage: 15Kv phase-to-phase.
      
   2. 
      Continuous current: 200 A RMS.
      
2. 
   Ground metallic cable shields with a device designed for that purpose, consisting of a solderless connector enclosed in watertight rubber housing covering the entire assembly.
   

1. 
   Provide insulated cable supports to relieve any strain imposed by cable weight or movement.
   

1. LOW-VOLTAGE EQUIPMENT

1. 
   Mount the low voltage bushings and hot stick in the low voltage compartment.
   
2. 
   The low-voltage leads shall be brought out of the tank by epoxy pressure tight bushings, and shall be standard arrangement per ANSI.
   
3. 
   Tin-plate the low-voltage neutral terminal and isolate from the transformer tank. Provide a removable ground strap sized in accordance with the NEC and connect between the neutral and ground pad.
   

1. TRANSFORMERS

1. 
   Transformers shall be three-phase, liquid-immersed, isolated winding, and self-cooled by natural convection.
   
2. 
   The kVA ratings shown on the drawings are for continuous duty without the use of cooling fans.
   
3. 
   Temperature rises shall not exceed the NEMA TR1 standards of 149˚ F [65˚ C] by resistance, and 180˚ F [80˚ C] hotspot at rated kVA.
   
4. 
   Transformer insulating material shall be mineral oil and shall be in accordance with ASTM D 3487.
   
5. 
   Transformer impedance shall be not less than 4.5% for sizes 150 kVA and larger. Impedance shall be as shown on the drawings.
   
6. 
   Sound levels shall conform to NEMA TR1 standards.
   
7. 
   Primary and Secondary Windings for Three-Phase Transformers:
   
   1. 
      Primary windings shall be wye-connected, unless noted otherwise on the drawings. Provide isolated neutral bushings for primary wye- connected transformers.
      
   2. 
      Secondary windings shall be wye-connected, except where otherwise
      

indicated on the drawings. Provide isolated neutral bushings for secondary wye-connected transformers.

1. 
   Secondary leads shall be brought out through pressure-tight epoxy bushings.
   
1. 
   Primary windings shall have four 2.55 full-capacity voltage taps; two taps above and two taps below rated voltage.
   
2. 
   Core and Coil Assemblies:
   
   1. 
      Cores shall be grain-oriented, non-aging, and silicon steel to minimize losses.
      
   2. 
      Core and coil assemblies shall be rigidly braced to withstand the stresses caused by rough handling during shipment, and stresses caused by any possible short-circuit currents.
      
   3. 
      Coils shall be continuous-winding type without splices except for taps. Material shall be copper.
      

1. 
   Coil and core losses shall be optimum for efficient operation.
   
2. 
   Primary, secondary, and tap connections shall be brazed or pressure type.
   
3. 
   Provide end fillers or tiedowns for coil windings.
   
1. 
   The transformer tank, cover, and radiator gauge thickness shall not be less than that outlined in ANSI.
   
2. 
   Accessories:
   
   1. 
      Provide standard NEMA features, accessories, and the following:
      
      1. 
         No-load tap changer (Provide warning sign).
         
      2. 
         Lifting, pulling, and jacking facilities.
         
      3. 
         Globe-type valve for oil filtering and draining, including sampling device.
         
      4. 
         Pressure relief valve.
         
      5. 
         Liquid level gauge and filling plug.
         
      6. 
         A grounding pad in the medium- and low-voltage compartments.
         
      7. 
         A diagrammatic nameplate and operating instructions enclosed by a transparent cover located in the low-voltage compartment.
         
      8. 
         Dial-type liquid thermometer with a maximum reading pointer and an external reset.
         
      9. 
         Hot stick. Securely fasten hot stick within low-voltage compartment.
         
   2. 
      The accessories shall be made accessible within the compartments without disassembling trims and covers.
      
3. 
   Transformers shall meet the minimum energy efficiency values per NEMA TP1:
   

KVA	(%)
75	98.1
112.5	98.3
150	99.0
225	99.0
300	99.0
500	99.1
750	99.2
1000	99.2
1500	99.3
2000	99.4
2500	99.4