The Electrical Distribution Architecture – Part One

Introduction :

Today, I will begin introducing and explaining the new course” 
EE-2: Basic Electrical design course – Level I " , the first topics in this course will be about how to: 

  • Determine the electrical requirements, needs or Characteristics for any building, these Characteristics will be used as inputs for the preliminary design phase or what we call “Draft Design Stage”
  • Provide different schematic diagrams with different connections configuration which will be suitable for the building electrical requirements, needs or Characteristics taken from point (1). 
  • Select optimal power sources and distribution network. 
  • Select the equipment from the manufacturers’ catalogues. 
  • Draw the final designed single line diagram. 

The best draft design (preliminary design) can be obtained by choosing the optimal solution resulted from mixing of:

  • The architect’s ideas that will define the organization of the building according to user requirements and building Characteristics. 
  • Ideas for The designers of different technical sections (lighting, heating, air conditioning, fluids, etc.), which will combine the user requirements and building Characteristics.
  • Requirements of The user’s representative. 
  • Requirements of Local Building regulations and codes which must be followed to get the local authorities approvals. 

Note: the best electrical system architecture is the one satisfying the various performance criteria that interest the customer who will use the building at different phases in its life cycle.

The process of Mixing and selecting optimal solutions for the above items is called "The architecture design process”.

Architecture design process Levels

The architecture design process is used only at the Draft Design stage. It generally covers the following levels (See Fig.1):

  1. MV/LV main distribution, 
  2. LV power distribution, 
  3. The terminal distribution level (as a general idea only). 

Fig (1) architecture design process Levels

Architecture design process Steps

The architecture design process includes 4-stage processes as follows (see fig.2):

  • Step (1): Choice of distribution architecture fundamentals, 
  • Step (2): choice of architecture details,
  • Step (3): choice of equipment,
  • Step (4): Assessment step.

Fig(2) architecture design process steps

Step (1): Choice of distribution architecture fundamentals

a- Step function:
Providing different schematic diagrams with different connections configuration for the utilities network, MV circuits, number of power transformers, number and distribution of transformation substations, MV back-up generator, etc.

b- Step Inputs:
  • The electrical Characteristics which based on the building type and its usage. 

c- Step Outputs:
At the end of this step, we have several distribution schematic diagram solutions, which are used as a starting point for the single-line diagram. The definitive and detailed single-line diagram is confirmed at the end of the step 2.

Step (2): choice of architecture details

a- Step function:
Defining the electrical installation in more detail by making choices for Centralized or decentralized distribution, Presence of back-up generators, Presence of uninterruptible power supplies, Configuration of LV circuits, etc.

b- Step Inputs:
  • Several distribution schematic diagram solutions obtained from step (1). 
  • Implementation and operation criteria of the building defined by all parties. 

c- Step loops:
The process loops back into step (1) if the Implementation and operation criteria of the building are not satisfied. An iterative process allows several assessment criteria combinations to be analyzed.

d- Step Outputs:
At the end of this step, we have a detailed single-line diagram.

Step (3): choice of equipment

a- Step function:
Selecting equipment from the manufacturers’ catalogues like MV/LV substation, MV switchboards, Transformers, LV switchboards, Busbar trunking, UPS units, Power factor correction and filtering equipment.

b- Step Inputs:
  • A detailed single-line diagram obtained from step (2). 
  • technological characteristics. 
  • manufacturer catalogues. 
  • Choices of architecture and other designer of different technical sections which must satisfy the technological characteristics/criteria. 

c- Step loops:
This stage is looped back into step 2 if the technological characteristics/criteria are not satisfied.

d- Step Outputs:
At the end of this step, we have a technological solution.

Step (4) : Assessment step

a- Step function:
This assessment step allows the Engineering Office to have figures as a basis for discussions with the customer, architect and other parties.

b- Step Inputs:
  • A technological solution obtained from step (3). 
  • Assessment Criteria. 
  • Optimization recommendations. 

c- Step Loops:
According to the result of discussions between the customer, architect and other parties based on this Assessment and after applying the Optimization recommendations
, it may be possible to loop back into step (1), step (2) or step (3). 

d- Step Outputs:
At the end of this step, we have a definitive and detailed Electrical Distribution architecture for the building under design. 

Application of Architecture design process:

The application of Architecture design process will include the following tasks:

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

I will begin to explain these tasks one by one in the following paragraphs and topics.

First: Assigning of electrical installation characteristics

Electrical installation characteristics are the main installation characteristics enabling the defining of the fundamentals and details of the electrical distribution architecture, and these characteristics will 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.

1- Activity of Building (see fig.3)

Main economic activity carried out on the site.

1.            Industrial buildings 

2.            Commercial buildings 

3.            Residential buildings 

4.            Agricultural buildings 

5.            Educational buildings 

6.            Transportation buildings 

7.            Religious buildings 

8.            Parking and storage 

9.            Military buildings 

10.         Governmental buildings 

11.         Cultural buildings 

12.         Other buildings

Fig (3) different activities for buildings

Please review the links in below for choice the right activity:

1- Industrial buildings Design Requirements:

2- Commercial buildings Design Requirements:

3- Health Care Facilities buildings Design Requirements:

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