In the previous Topic “The Electrical Distribution Architecture – Part Three“ , 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:
- Activity,
- Site topology,
- Layout latitude,
- Service reliability,
- Maintainability,
- Installation flexibility,
- Power demand,
- Load distribution,
- Power Interruption Sensitivity,
- Disturbance sensitivity,
- Disturbance capability of circuits,
- 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:
8- Load distribution
#
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Characteristic
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Definition
|
Choice
|
|
8
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Load Distribution
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A
characteristic related to the uniformity of load distribution (in kVA / m²)
over an area or throughout the building.
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Uniform
distribution: the
loads are generally of an average or low unit power and spread throughout the
surface area or over a large area of the building (uniform density).E.g.:
lighting, individual workstations
|
|
Intermediate
distribution: the
loads are generally of medium power, placed in groups over the whole building
surface area. E.g.: machines for assembly, conveying, workstations, modular
logistics “sites”
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|||
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localized
loads: the loads are generally
high power and localized in several areas of the building (non-uniform
density).E.g.: HVAC
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The following table summarizes the effect of Load distribution Method on the Configuration of Electrical Distribution Architecture:
Configuration of Electrical Distribution Architecture
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Loads Distribution
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||
Localized Loads
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Intermediate Distribution
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Uniform Distributed
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Layout#1
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Layout#1
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Layout#2
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Layout#2
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Layout#1 (see fig.1): 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.1): 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 (1): effect of Load distribution Method on the Configuration of Electrical Distribution Architecture |
9- Power Interruption Sensitivity
#
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Characteristic
|
Definition
|
Choice
|
|
9
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Power Interruption Sensitivity
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The
aptitude of a circuit to accept a power interruption.
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“Sheddable”
circuit:
possible to shut down at any time for an indefinite duration
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Long interruption
acceptable:
interruption time > 3 minutes *
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Short
interruption acceptable:
interruption time < 3 minutes *
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No interruption
acceptable.
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*
Indicative value, supplied by standard EN50160: “Characteristics of the
voltage supplied by public distribution networks”.
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We can distinguish various levels of severity of an electrical power interruption, according to the possible consequences:
- No notable consequence,
- Loss of production,
- Deterioration of the production facilities or loss of sensitive data,
- Causing mortal danger.
and This is expressed in terms of the criticality of supplying of loads or circuits as follows:
- Non-Critical: The load or the circuit can be “shed” at any time. E.g.: sanitary water heating circuit.
- Low Criticality: A power interruption causes temporary discomfort for the occupants of a building, without any financial consequences. Prolonging of the interruption beyond the critical time can cause a loss of production or lower productivity. E.g.: heating, ventilation and air conditioning circuits (HVAC).
- Medium Criticality: A power interruption causes a short break in process or service. Prolonging of the interruption beyond a critical time can cause a deterioration of the production facilities or a cost of starting for starting back up. E.g.: refrigerated units, lifts.
- High Criticality: Any power interruption causes mortal danger or unacceptable financial losses. E.g.: operating theatre, IT department, security department.
and The following table summarizes the suitable Power Interruption Sensitivity for different Configurations of Electrical Distribution Architecture (Supply side of Transformers) (see fig.2):
Power Interruption
Sensitivity
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||||||
Long interruption acceptable
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Short interruption acceptable
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|||||
Power Demand
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<
630KVA
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≤
1250KVA
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≤
2500KVA
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>
2500KVA
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>
2500KVA (And Several Buildings)
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Configuration Of Electrical Distribution Architecture
(Supply side of Transformers)
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LV
(No Transformers)
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MV
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||||
Single-Line / Single Feeder
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Ring-Main
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Duplicate Supply / Open Ring 1 MV Substation
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Duplicate Supply With Double Busbars / Open Ring 2 MV
Substations
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|||
Fig (2):Configurations of Electrical Distribution Architecture (Supply side of Transformers) |
and The following table summarizes the suitable Power Interruption Sensitivity for different Configurations of Electrical Distribution Architecture (Load side of Transformers) (see fig.3):
Power Interruption Sensitivity
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|||||||
Long interruption acceptable
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Short or No interruption acceptable
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Long interruption acceptable
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Shedd
able
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||||
Power Demand
|
<
630
KVA
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≤
1250
KVA
|
≤
2500
KVA
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≤
2500KVA
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>
2500
KVA
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>
2500
KVA
(And Several Buildings)
|
Any
|
Configuration Of Electrical Distribution Architecture
(Load side of Transformers)
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Radial
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Radial
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-
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Double Ended
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Ring
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Ring
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Shedd
able Load
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Two-Pole
Configuration
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|||||||
Two-Pole
Configuration
With Two
½ MLVS And No
Link
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|||||||
-
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Interconnected Switchboards
|
Fig (3): Configurations of Electrical Distribution Architecture (Load side of Transformers) |
10- Disturbance sensitivity
#
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characteristic
|
Definition
|
choice
|
|
10
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Disturbance sensitivity
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The
ability of a circuit to work correctly in presence of an electrical power
disturbance.
|
|
Low
Sensitivity:
disturbances in supply voltages have very little effect on operations. E.g.:
heating device.
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|
Medium Sensitivity:
Voltage
disturbances cause a notable deterioration in operations. E.g.: motors,
lighting.
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|||
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High
Sensitivity:
Voltage
disturbances can cause operation stoppages or even the deterioration of the
supplied equipment. E.g.: IT equipment.
|
Types of disturbances with an impact on circuit operations:
- Brown-outs,
- Over voltages,
- Voltage distortion,
- Voltage fluctuation,
- Voltage imbalance.
Effect of Disturbance sensitivity value on Configuration of Electrical Distribution Architecture:
The sensitivity of circuits to disturbances determines the design of shared or dedicated power circuits. Indeed it is better to separate “sensitive” loads from “disturbing” loads. E.g.: separating lighting circuits from motor supply circuits. This choice also depends on operating features. E.g.: separate power supply of lighting circuits to enable measurement of power consumption.
And the following table summarizes the suitable Disturbance sensitivity value for different Configurations of Electrical Distribution Architecture (Load side of Transformers)( see fig.3):
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Disturbance sensitivity value
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|||||
Low Sensitivity
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High Sensitivity
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|||||
Configuration Of Electrical Distribution Architecture
(Load side of Transformers)
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Radial
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Sheddable Load
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Two-Pole
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Interconnected Switchboards
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Ring
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Double Ended
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11- Disturbance capability of circuits
#
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Characteristic
|
Definition
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Choice
|
|
11
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Disturbance capability of circuits
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The
ability of a circuit to disturb the operation of surrounding circuits due to
phenomena such as: harmonics, in-rush current, imbalance, High Frequency
currents, electromagnetic radiation, etc.
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Non Disturbing
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Moderate Or Occasional Disturbance
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|||
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Very disturbing
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This characteristic is related to the above characteristic “Disturbance sensitivity” for far extent and they must be studied together for obtaining an optimal Configuration of Electrical Distribution Architecture.
The following table summarizes the effect of Disturbance capability of circuits on Configuration of Electrical Distribution Architecture (Load side of Transformers):
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Disturbance
Capability Of Circuits Value
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Non Disturbing
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Moderate Or Occasional Disturbance
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Very disturbing
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Action Taken For Configuration Of Electrical
Distribution Architecture (Load Side Of Transformers)
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no specific precaution to
take
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Separate power supply may
be necessary in the presence of medium or high sensitivity circuits. E.g.:
lighting circuit generating harmonic currents.
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A dedicated power circuit
or ways of attenuating disturbances are essential for the correct functioning
of the installation. E.g.: electrical motor with strong start-up current, welding
equipment with fluctuating current.
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In the next topic, I will continue explaining other Electrical installation characteristics and Technological characteristics. So, please keep following.
م علي
ReplyDeleteشكرا علي مجهوداتك التي لن لن تنكر بإذن الله
وأرجو منك تبني مشروع متكامل تتعرض فيه لتطبيق هذه القواعد في صورتها العملية مثل وثائق المشروع الحسابية والرسومات فإنها كفيلة لإكساب المتعلمين مثلي الثقة اللازمة قبل البحث والقراءة المجردة عن التطبيق
eng. shady
ReplyDeleteshortly, I will post a complete electrical design for one project and I will provide design criteria, the calculation sheets ,drawings, specs, etc. but after explaining the basis for doing this electrical design as I try to do here in my design courses.
so, please keep following and you will get your request.