Forced Ventilation(Only for basement transformer rooms)

11.6 Forced Ventilation(Only for basement transformer rooms)

1. 
   Must have minimum two sides ventilation with aluminum louver doors and fixed aluminum louvers window. Fixed aluminum louver window(s) should be at 0.6m above outside level.
   
2. 
   Total minimum Grill area is 14.9 m² for 1000kVA transformer and 18.6m² for 1500kVA transformer.
   
3. 
   Adequate independent mechanical ventilation to be provided as per requirements for transformer room at basement level by providing calculations supporting the adequacy of mechanical ventilation proposed for maintaining the ambient temperature in the substation at maximum of 55 deg C based on outside air temperature of 48 deg C. [Appendix 18].
   

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7. Methods of equipment transportation to Basement Transformer rooms

7. 
   Substation cable arrangement (subject to DEWA design)
   

1. 
   Cutout at 0.95m depth from outside level (towards road/sikka) should be provided for HV cable entry. [Appendix 15]
   
2. 
   Cable route/arrangement from plot limit to the Substation (if setback confirmed in affection plan issued by competent authority) to be through cable trench with removable slab as per DEWA section TT [Appendix 19] or cable tray at high level basement.
   
3. 
   If cables not passing through traffic area, buried cables or cable ducts along with manholes at both ends can be proposed subject to DEWA approval.
   
4. 
   Cable trench inside substation should have a clear depth of 0.95m from finished floor of substation. [Appendix 15]
   
5. 
   For basement/split substation, transformer room cable trench depth of 0.50m from finished floor can be acceptable subject to DEWA approval.
   
6. 
   For cable tray arrangement clear depth of 0.95m from finished floor of Substation up to bed of the tray with minimum clear depth of 0.45m between bottom of the slab and the bed of the tray.
   
7. 
   Cable installation/maintenance space of minimum 1.2m to be provided at least one side in case of cable tray arrangement.
   

8. 
   The cable tray should pass through public/open area and not through any closed area / room (there shall be no services, pipes, etc. below the cable tray).
   
9. 
   Cable route from RMU to transformer room is preferred to be straight (Without turns / bends) (the bending radius to be considered R= 0.95m if any)