The Electrical Distribution Architecture – Part Three


In the previous Topic “ The Electrical Distribution Architecture – Part Two “ , I list the Tasks required for application of Electrical Distribution architecture design process , they were: 

  • Assigning of electrical installation characteristics,
  • Assigning of Technological characteristics,
  • Using Architecture assessment criteria,
  • Step (1): Choice of distribution architecture fundamentals,
  • Step (2): choice of architecture details,
  • Step (3): choice of equipment,
  • Recommendations for architecture optimization.

And I began explaining the first task: Assigning of electrical installation characteristics which include the following categories or possible values:

  1. Activity,
  2. Site topology,
  3. Layout latitude,
  4. Service reliability,
  5. Maintainability,
  6. Installation flexibility,
  7. Power demand,
  8. Load distribution,
  9. Power Interruption Sensitivity,
  10. Disturbance sensitivity,
  11. Disturbance capability of circuits,
  12. Other considerations or constraints.

Today, I will continue explaining other tasks for helping you to use Electrical Distribution architecture design process professionally.

You can review the following previous topics for more information and good following:




5- Maintainability




#
characteristic
Definition
choice
5
Maintainability
Features input during design to limit the impact of maintenance actions on the operation of the whole or part of the installation.

Minimum: the installation must be stopped to carry out maintenance operations.

Standard: maintenance operations can be carried out during installation operations, but with deteriorated performance. These operations must be preferably scheduled during periods of low activity.

Enhanced: special measures are taken to allow maintenance operations without disturbing the installation operations.

The Maintainability level is determined to be (minimal, standard and enhanced) based on the following factors: 

  1. The Activity importance of the building. 
  2. The site topology of the building. 
  3. The power demand of the building. 

The following table summarizes the effect of these factors on the Maintainability level and fig (1) represents the Configuration of Electrical Distribution Architecture in each case:




Characteristic To Consider
Configuration of Electrical Distribution Architecture (Supply side of Transformers)
LV
(No Transformers)
MV
Single-Line / Single Feeder
Ring-Main
Duplicate Supply / Open Ring 1 MV Substation
Duplicate Supply With Double Busbars / Open Ring 2 MV Substations
Activity
Any
Any
Any
Hi-tech, sensitive Office, Health-Care
Any
Site Topology
Single Building
Single Building
Single Building
Building With One Level or Several Buildings
Several Buildings
Power Demand
< 630kva
≤ 1250kva
≤ 2500kva
> 2500kva
> 2500kva
Maintainability
Minimal
Minimal or Standard
Standard
Enhanced
Enhanced



Fig (1): Configuration Of Electrical Distribution Architecture (Supply side of Transformers)


6- Installation flexibility


#
characteristic
Definition
choice
6
Installation Flexibility
Possibility of easily moving electricity delivery points within the installation, or to easily increase the power supplied at certain points. Flexibility is a criterion which also appears due to the uncertainty of the building during the pre-project summary stage.

Examples:
 - Industrial building: extension, splitting and changing usage.
- office building: splitting
   

No flexibility: the position of loads is fixed throughout the lifecycle, due to the high constraints related to the building construction or the high weight of the supplied process. E.g.: smelting works.

Flexibility of design: the number of delivery points, the power of loads or their location are not precisely known.

Implementation flexibility: the loads can be installed after the installation is commissioned.

Operating flexibility: the position of loads will fluctuate, according to process re-organization.


The Installation Flexibility level is based on the following factor:

  1. Method of Loads distribution in each floor. 


Method of Loads distribution in each floor will be one of the following types:
  1. Localized Loads: localized in certain, fixed and separated positions. 
  2. Intermediate distribution: Localized in certain positions but distributed along the floor. 
  3. Uniform distributed: loads spread out along the floor. 

The following table summarizes the effect of Installation Flexibility level and Method of Loads distribution on the Configuration of Electrical Distribution Architecture:


Installation Flexibility Level
Loads Distribution
Localized Loads
Intermediate Distribution
Uniform Distributed
No Flexibility
Layout#1
Layout#1
Layout#2
Design Flexibility
Implementation Flexibility
Layout#2
Operation Flexibility

Where:

Layout#1 (see fig.2): The Electrical Distribution Architecture will be that each final load or final panelboards has its directly connected cable to the main low voltage switchgear.

Layout#2 (see fig.2): The Electrical Distribution Architecture will be that many loads or final panelboards will be connected to a busway or bus trunking system directly connected to the main low voltage switchgear.

Fig (2)


7- Power Demand

#
Characteristic
Definition
Choice
7
Power demand
The sum of the apparent load power (in kVA), to which is applied a usage coefficient. This represents the maximum power which can be consumed at a given time for the installation, with the possibility of limited overloads that are of short duration.

< 630 kVA

630 – 1250 kVA

1250 -  2500 kVA

> 2500 kVA

The following table, fig (1) in above and fig (3) summarize the effect of Power Demand on the Configuration of Electrical Distribution Architecture:


Power Demand
< 630KVA
≤ 1250KVA
≤ 2500KVA
> 2500KVA
> 2500KVA (And Several Buildings)
Number Of Transformers
1
1
> 1
> 1
> 1
Number Of MV/LV Transformer Substation
1
1
1
> 1
> 1
Configuration Of Electrical Distribution Architecture (Supply side of Transformers)
LV
(No Transformers)
MV
Single-Line / Single Feeder
Ring-Main
Duplicate Supply / Open Ring 1 MV Substation
Duplicate Supply With Double Busbars / Open Ring 2 MV Substations
Configuration Of Electrical Distribution Architecture (Load side of Transformers)
Radial
Radial
-
Ring
Ring
Two-Pole Configuration
Two-Pole Configuration With Two ½ MLVS And No Link
-
Interconnected Switchboards
-
Double Ended


fig (3): Configuration Of Electrical Distribution Architecture (Load side of Transformers)


In the next topic, I will continue explaining other Electrical installation characteristics. So, please keep following. 




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