# Power System Architectures for the Commercial Buildings – Part Three

In the previous Topic; Power system architectures for the commercial buildings – Part Two , I explained the Second type of Power system architectures for the commercial buildings which was “Low building, type 2: Two supply sections” and today I will explain the third type; High-rise building, type 1&2: Central power supply, cables/Busbars as follows.

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

High-rise building, type 1&2 : Central power supply, cables/Busbars

Conditions for using this power system architecture:

1- If the following rule is verified:

The number of building floors must not exceed the max. Number of floors for High-rise building, type 1: Central power supply, cables (i) calculated by equation#1.

If:

Max. Side length of the building = a (in meter)

One Floor area A = a2 (in square meter)

Height per floor = h (in meter)

Then:

Max. Number of floors for one supply section (i) ≤ (100 – 2a) / h          (equation#1)

If the number of floors exceed the max. Number of floors for "High-rise building, type 1: Central power supply, cables " (i) calculated by equation#1, then we must use other types of power system architecture.

Notes:
• The max. Number of floors for High-rise building, type 1: Central power supply, cables (i) must be ≤ 10.
• All buildings have number of floors > 4 are high rise buildings.

2- If the (Ground area / total area) of the building ≤ 1,000 m2 / 10,000 m2.

3- If the power density of the building loads have the following limits:
• Power required ≤ 2,000 kVA.
• 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 1: Central power supply, cables” power system architecture:

We have a building with 1,000 KVA total load power, 10 floors and floor area 1,000 m2 with total area 10,000 m2.

Solution selected for this building is using the “ High-rise building, type 1: Central power supply, cables” power system architecture as follows:

 Design solution Advantages of this solution Benefits from this solution Using Central transformer supply close to load center Simple network configuration, low power losses Only one electric utilities room required, easy and low-cost operation of electric system Radial network Transparent structure Easy operation and fault localization Transformer module with 2 × 630 kVA, Voltage stability, lighter design Optimized voltage quality, economical Redundant supply unit: – Generator 400 kVA (30 %) (the smaller the generator, the greater the short-circuit current must be compared to the nominal current) – UPS 200 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 system) 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 1: Central power 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 2: Central power supply, busbars” And the Solution selected for this building is using the “ High-rise building, type 1: Central power supply,
busbars ” power system architecture as follows:

 Design solution Advantages of this solution Benefits from this solution Using Central transformer supply close to load center Simple network configuration, low power losses Only one electric utilities room required, easy and low-cost operation of electric system Radial network Transparent structure Easy operation and fault localization Transformer module with 2 × 630 kVA, Optimized voltage stability Operation that is gentle on the user's equipment, economical equipment Redundant supply unit: – Generator 400 kVA (30 %) (the smaller the generator, the greater the short-circuit current must be compared to the nominal current) – UPS 200 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 system) 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 Central measurement of current, voltage, power, e.g. for billing, cost center allocation Safety, time savings during restructuring Few branches 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 saving

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

 “ High-rise building, type 1: Central power supply,  busbars ” power system architecture

In the next Topic, I will explain the “High-rise building, type 3: Transformers at remote location” power system architecture. So, please keep following