LABELLING & IDENTIFICATION

SECTION – 11

1. 
   MV Network Design requirements (11-22 KV)
   

1. 
   Ring Supply consisting of two feeders (two-feed ring) is mainly granted for power supply as normal feeding arrangement. Three-feed ring arrangement may be adopted for cases where all MV switchgears/ RMUs are installed in one location to ensure the specific supply reliability.
   
2. 
   For reliable power supply; N-1 offline criterion is considered. Hence, in case of power failure in one of the feeders, the other feeder should be capable to meet whole demand for maximum 6 hours duration.
   

3. 
   DEWA standard 11 kV cable sizes are 3/C 300mm² Copper XLPE, 3/C 240mm² Copper XLPE, and 3/C 240mm² Aluminum XLPE. DEWA standard 22 kV cable size is 3/C 300mm² Aluminum XLPE.
   

4. 
   The maximum sustained load of 11kV feeder is 175A/3MW (for 300mm² Copper XLPE cables – summer rating).
   

5. 
   The maximum sustained load of 11kV feeder is 160A/2.7MW (for 240mm² Copper XLPE cables – summer rating).
   

6. 
   The maximum sustained load of 22kV feeder is 165A/5.6MW (for 300mm2 Aluminum XLPE cables – summer rating).
   

7. 
   For bulk loads such as furnaces or district cooling requiring direct HV supply (private equipment's), space for metering units at party’s premises/substation shall be considered. Necessary documents, drawings and SLD shall be submitted for comments/approval at design stage.
   

8. 
   Single unit load demand shall not exceed the maximum sustained current of MV cable/feeder, which is maximum 175A/3MW for 11kV feeder and 165A/5.6MW for 22kV feeder.
   

9. 
   Parallel operation of MV feeders are not allowed at any circumstances, and accordingly proper interlocking (Electrical & Mechanical) shall be provided wherever required.
   

10. 
    Standby generators are not allowed to operate in parallel with network. Therefore, proper interlocking shall be provided where it is required.
    

11. 
    Comply with the planning levels of voltage flicker based on IEC 61000. Accordingly, voltage dip calculations during motor starting shall be submitted along with the motor specification, starting characteristics, number of motor starts per day, SLD drawings etc. for approval at design stage.
    

12. 
    For loads that injects harmonics currents into network, harmonic study shall be prepared and approved at the design stage, to comply with the planning limits of Harmonic Emissions for voltage and current based on IEC 61000-3-6: ed2.0-2008 and IEC 61000–3-12: ed2.0-2011 respectively.
    

13. 
    Harmonics and Flickers measurements shall be conducted after commissioning of project and report of measurements shall be submitted.
    

14. 
    Maximum allowable number of cables per trench for 11kV cables is 20 arranged in maximum two layers. (2.5 to 3-meter trench width on both sides of the road, close to 132/11kV S/S and 2.0/1.5 meters elsewhere depending on load distribution).
    

15. 
    Maximum allowable number of cables per trench for 22kV cables is 10 arranged in maximum one layer. (2.5 to 3-meter trench width close to 132/22kV S/S and 2.0 meter elsewhere).
    

16. 
    Clearance of minimum 2 meters shall be maintained between any MV cable trench and the surrounding heat sources such as 132kV cable trench.
    

17. 
    Horizontal spacing between MV cables is 150mm (edge to edge for MV cables) and vertical spacing between layers is 100mm (edge to edge applicable for 11kV cables).
    

18. 
    Separate corridor shall be allocated for MV cable laying within project’s premises along the road to ensure avoiding crossing between 132kV and MV cables.
    

19. 
    Backfilling to be used for MV cables with soil resistivity below 1.6⁰C-m/W with the following conditions:
    
    1. 
       At maximum moisture content of 2% or less.
       
    2. 
       At 90% of compaction
       

20. 
    Single line diagram illustrating the protection schemes along with relay setting calculation shall be submitted for comments and approval at design stage.
    

2. General Requirements for Substation Construction within Private plot

1. 
   The substation must be positioned in dedicated room or housing.
   

2. 
   Basement substation should have transformer room in 1^st basement only.
   
3. 
   LV electrical room must be adjacent to substation room/space, if main panel is private.
   

4. 
   Wet area above substation shall not be provided. In exceptional unavoidable situation DEWA shall be referred for specific advice refer Appendix. 13.
   

5. 
   Single room substation clear height should be 3.7M (minimum) at ground floor. RMU room should have a clear height of 3.0m (minimum) in split/basement substation.
   

6. 
   Transformer room height at basement should be 3.0m (minimum).
   

7. 
   Finished floor level (FFL) of substation room is to be maintained 0.15m to 0.30m higher than the outside adjacent ground level (towards door side) refer [Appendix 14- 15]
   

8. 
   Level difference of transformer room at basement level is to be maintained between 0.075m to 0.15m higher than the outside adjacent ground level (towards door side).
   

9. 
   Construction of the project should not be commenced prior to obtain the substation approval.
   

10. 
    Pocket substations are not allowed to install at petrol station and inside the building.
    

11. 
    No expansion joints are allowed in RMU/Transformer room and as well as roof of the room.
    

11.3 Substation Location & Access

1. 
   Substation room/RMU room to be directly located on RTA/Public Road or Sikka.
   

2. 
   In case Substation/RMU room is located on Sikka, the sikka should have a minimum clear width of 6.1m. However if the proposed RMU room location is less than 12m away from the main road then the sikka can be accepted with minimum clear width of 3.0m.
   
3. 
   24 hours DEWA direct open to sky access from the plot limit to the Substation/RMU room (if setback confirmed in affection plan issued by competent authority) shall be provided.
   
4. 
   In case of split room/basement room arrangement transformer room can be located on internal driveway having a clear 3.0m wide & 3.0 high and direct access from RTA road.
   

Page 3 of 9

11.4 Substation Types and Area

1. 
   Single Room Substation (RMU & Transformer in same room Ground Floor)
   

Area	33 m2	For 1x1000/1500 KVA transformer (minimum width of 4.57m)
	54 m2	For 2x1000/1500KVA transformers (minimum width of 6.1m)
	25 m2	Extra space for every additional transformer
	10 m2	Extra space required for four and above transformers (additional equipment’s)

2. 
   Split room Substation (RMU & Transformer In separate rooms Ground Floor)
   

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