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Need help with Mxxumium Demand and design

1323 Views 5 Replies 5 Participants Last post by  kkboy
Hi Guys and girls. I live in Australia and have to do a electrical installation design for school. Can anyone help me with it please.
Must be australian standards thanks

Electrical installation planning

The Commercial/Industrial complex consists of 4 units. The main switchboard is supplied by a service line from a 400/230v, 750kA transformer located 0.3km from the complex. The PSC (A-N) at the point of supply is stated as 12.8kA. The complex has one MEN at the main board. The metering for each unit is at the switchboard.

The sub boards to unit 1,2,3 in the complex are supplied by X90 multicore cables with circular copper conductors and installed unenclosed and touching in a common trench as a category B underground wiring system. The cables are laid in sand and protected with concrete slabs and have 800mm of cover. The sub board in unit 4 is supplied from the main switchboard as a separate underground wiring system in its own trench.

The metering sub main to unit 1 is 48 meters from the main board.
The advertising sign is supplied from the main board and has a cable length of 125 meters and is installed in the same trench as the sub mains to units 1,2, and 3.













LOAD GROUP ITEM DESCRIPTION DISTRIBUTION Calculation Phase Calculated MD
A B C A B C
18 Lighting 350W Mercury Vapor 1.5A 6 6 6
1 Advertising Sign X
24 Double 10A Outlets 10 7 7
9 Single 15A Outlets 3 3 3
2 3 Phase 15A Outlets X
X X
X X
X
3 3Phase Motors (6.8A) X
X
X X
X
X X
X
X
1 3 Phase Air-con @ 35A X X X
2 3.6kW HW instant X
X X
X
TOTAL














2) Select the appropriate cable sizing using AS3008.1 for the sub mains taking into account the method of installation. Fill in the information relating to the tables and columns in AS3008.1

Tb.____ Item No._____
Tb_____ Item No______

What (if any) de ratings apply.

TABLE ITEM COLUMN DE-RATING DE_RATING CONDITION



Show all working out








Select a Cable from the Table to Satisfy these requirements.



Selected Cable Size_______________mm2

3) Calculate the voltage drop for the installation so that the cable size chosen meets the current carry capacity and the voltage drop requirements.
You are allowed a 0.9% voltage drop for this sub main. Show all working out.






Calculated Voltage Drop for the proposed cable =

Permitted Voltage Drop =
Cable Rating of cable as installed in this installation __________A

4) Select the maximum allowable circuit breaker to protect the 3Phase Sub-mains. A list of Available circuit breakers is shown below.

Circuit Breaker Rating ____________A

20 125 350
25 160 400
32 175 450
40 200 500
50 225 550
80 250
100 300




5)What is the maximum kA rating of the circuit breakers installed in the switchboard (in unit 1) to protect final sub circuits? (A-N values) show working out.







Rating ________________________________

6) Calculated the maximum allowable operating internal fault loop impedance for the sub-mains. (show all working out)






Internal Fault Loop Impedance- ____________________

7) Using AS3008.1 Calculate the actual resistance of the Earth wire when measured from MEN to the sub board earth link Prior to connection to the supply. Show working out.



Actual Resistance- _______________
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Hi Jt2013
I can certainly help you out and check your answers. Let me know what your stuck on and i will prompt you in the right direction. Dont worry about what others say on here, i think its just an Electricians attitude. I havent met a smart eletrician yet. WHen i was doing my refrigertaion trade i was told you had to have your brain removed to ba an electrician. I didnt believe that until i worked with a few and to this day i dont know how they got there license as simple problems they could not solve. Im assuming thats why no one is trying to help you out as really they dont know the answer. my email is [email protected]
Just send me what you have done and i will have a look. Im a thermal dynamic engineer but have worked out electrical assemments before. I suggest you change your trade to refrigeration after your apprenticeship finishes. Much more money and satisfaction.
 
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