Power System Architectures for the Commercial Buildings – Part Four

In the previous Topic; Power system architectures for the commercial buildings – Part Three, I explained the first type of Power system architectures for the commercial buildings which was “High-rise building, type 1&2: Central power supply, cables/Busbars” and today I will explain the forth type; High-rise building, type 3: Transformers at remote location as follows.

You can also review previous topics about electrical design requirements for commercial buildings for good following-up:

High-rise building, type 3: Transformers at remote location

Conditions for using this power system architecture: 

1- The max. Number of floors for this power system architecture (i) must be (10 < i ≤ 20) (i.e. i =10 to 20 floors)

Note: All buildings have number of floors > 4 are high rise buildings.

2- If the (Ground area / total area) of the building ≤ 1,000 m2 / 20,000 m2

3- If the power density of the building loads have the following limits:

  • Power required ≥ 1,500 kW.
  • Segmentation of power required 80 % utilized area (i.e. functional area like Offices, Briefing rooms, Data center, Canteen kitchen with casino, Heating/ventilation/air conditioning, Fire protection and Transport) And 20 % side area (i.e. shafts, fountains, green area, sky lighting area and etc.).

4- If the power supply needed for the building have the following requirements:

  • Supply types 100 % total power from the public grid; (Supply of all installations and consumer Devices available in the building).
  • 10–30 % of the total power for safety power supply (SPS) from generators; (Supply of life-protecting facilities in case of danger, e.g.: Safety lighting, Elevators for firefighters, Fire-extinguishing equipment).
  • 5–20 % of the total power for uninterruptible power supply (UPS); (Supply of sensitive consumer devices which must be operated without interruption in the event of a NPS failure / fault, e.g.: Tunnel lighting, airfield lighting, and Servers / computers and Communications equipment).

Example for using “High-rise building, type 3: Transformers at remote location” power system architecture:

We have a building with 1,800 KVA total load power, 15 floors and floor area 1,000 m2 with total area 15,000 m2.

Solution selected for this building is using the 
"High-rise building, type 3: Transformers at remote location” power system architecture as follows: 

Design solution
Advantages of this solution
Benefits from this solution
Splitting into two supply sections

Short LV cables, low power losses, reduction of fire load

Economical, simplified fire

Radial network

Transparent structure

Easy operation and fault localization

2 Transformer module with 2 +1 X 630 kVA, (distributed Transformers)

Voltage stability, lighter design

Optimized voltage quality,

Redundant supply unit:
– Generator 800 kVA (30 %) (the smaller the generator, the greater the short-circuit current must be compared to the nominal current)
– UPS 400 kVA (15 %)

Supply of important consumers on all floors in the event of a fault, e.g. during power failure of the public grid
Increased reliability of supply

Safety power supply

Safety power supply in acc. With DIN VDE 0100-718

Supply of sensitive and important consumers

Uninterruptible supply of
consumers, e.g. during power failure of the public grid

Use Medium-voltage switchgear from type SF6 gas-insulated

Compact Design; independent of climate

Minimized space requirements for
electric utilities room; no
maintenance required

Use Transformer from type cast-resin with reduced losses

Low fire load, indoor installation


Use Low-voltage main distribution with  central grounding point
( which splitting of PEN in PE and N to the TN-S sys (4-pole switches at the changeover points)

EMC-friendly power system

Protection of telecommunications
Equipment from electromagnetic
interference (e.g. to prevent lower transmission rates at communication

Use Wiring / main route as cables

Measurement of current, voltage, power, e.g. for billing, centrally per floor in LVMD

Central data processing

For this example the power system architecture will be as follows:

"High-rise building, type 3: Transformers at remote location” power system architecture

Normal power supply
Floor distribution boards
Power company or system operator
Heating – Ventilation – Air conditioning
Medium-voltage switchboard
Low-voltage main distribution
Safety power supply
Uninterruptible power supply
Power monitoring system

In the next Topic, I will explain the “High-rise building, type 4&5: Distributed supply, cables /Busbars ” power system architecture. So, please keep following.

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