Power System Architectures for the Commercial Buildings – Part Five

In the previous Topic; Power system architectures for the commercial buildings – Part Four, I explained the forth type of Power system architectures for the commercial buildings which was “High-rise building, type 3: Transformers at remote location” and today I will explain the fifth type; High-rise building, type 4 & 5: Distributed supply, cables/Busbars” as follows.

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

• General Electrical Design Requirements for Commercial Buildings

• Specific Electrical Design Requirements for Commercial Buildings

• Power system architectures for the commercial buildings – Part One

• Power system architectures for the commercial buildings – Part Two

• Power system architectures for the commercial buildings – Part Three

High-rise building, type 4 & 5: Distributed supply, cables/Busbars

Conditions for using this power system architecture: 

1- The max. Number of floors for this power system architecture (i) must be (i >20).

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


2- If the floor area of the building ≤ 1,000 m2 & the total area of the building > 20,000 m2

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

• Power required ≥ 2,000 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 4 & 5: Distributed supply, cables” power system architecture:

We have a building with 3,600 KVA total load power, 25 floors and floor area 1,000 m2 with total area 25,000 m2.

Solution selected for this building is using the “High-rise building, type 4: Distributed supply, cables” power system architecture as follows:

Design solution	Advantages of this solution	Benefits from this solution
Using distributed transformers Splitting into two supply sections	Short LV cables, low power losses, reduction of fire load	Economical, simplified fire protection
Radial network	Transparent structure	Easy operation and fault localization
(2)Transformer module with 3 × 630 kVA each	Voltage stability, lighter design	Optimized voltage quality, economical
Redundant supply unit: – Generator 500 kVA (30 %) (the smaller the generator, the greater the short-circuit current must be compared to the nominal current) – UPS 2x250 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	Economical
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 for connecting the LVMDs)	EMC-friendly power system	Protection of telecommunications Equipment from electromagnetic interference (e.g. to prevent lower transmission rates at communication lines)
Use Wiring / main route as cables	Central measurement of current, voltage, power, e.g. for billing, cost center allocation	Cost transparency, cost saving

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

“High-rise building, type 4: Distributed supply, cables” power system architecture

 

Where:

NPS	Normal power supply
FD	Floor distribution boards
PCO	Power company or system operator
FF	Firefighters
HVAC	Heating – Ventilation – Air conditioning
MS	Medium-voltage switchboard
LVMD	Low-voltage main distribution
SPS	Safety power supply
UPS	Uninterruptible power supply
z	Power monitoring system

The same power system architecture can be used but with Wiring / main route as busbars and in this case it will be called as “High-rise building, type 5: Distributed supply, busbars” And the Solution selected for this building is using the “High-rise building, type 5: Distributed supply, Busbars” power system architecture as follows:

Design solution	Advantages of this solution	Benefits from this solution
Using distributed transformer Splitting into two supply sections	Short LV cables, low power losses, reduction of fire load	Low costs
Radial network	Transparent structure	Easy operation and fault localization
(2) Transformer module with 3 × 630 kVA each	Optimized voltage stability	Optimized voltage quality, economical
Redundant supply unit: – Generator 500 kVA (30 %) (the smaller the generator, the greater the short-circuit current must be compared to the nominal current) – UPS 2x250 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	Economical
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 for connecting the LVMDs)	EMC-friendly power system	Protection of telecommunications Equipment from electromagnetic interference (e.g. to prevent lower transmission rates at communication lines)
Use Wiring / main route as Busbars to the sub-distribution boards	Low fire load, flexible power distribution	Safety, time savings during restructuring
	Few outgoing feeders in the distribution, small distribution	Minimized space requirements for electric utilities room
	Small, minimized rising main busbar	Less space requirements for supply lines
	Easy installation	Cost reduction

By using busars and for this example the power system architecture will be as follows:

“High-rise building, type 5: Distributed supply, Busbars” power system architecture

 

Where:  

NPS	Normal power supply
FD	Floor distribution boards
PCO	Power company or system operator
FF	Firefighters
HVAC	Heating – Ventilation – Air conditioning
MS	Medium-voltage switchboard
LVMD	Low-voltage main distribution
SPS	Safety power supply
UPS	Uninterruptible power supply
b	4-pole switch for connecting the LVMDs
z	Power monitoring system

In the next Topic, I will show complete comparison between these power system architectures for commercial buildings. So, please keep following