Download - IBTM601a Presentation v5
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Department of Mechanical Engineering
Master of Science in Intelligent Building Technology
and Management
IBTM 601A Electrical Facilities in Intelligent Buildings
Group Project
Busbar Volt Drop In The Building
THE HONG KONG UNIVERSITY OF SCIENCE AND TECHNOLOGY
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CONTENT
1. Introduction
2. Problem
3. Investigation Results
4. Improvement
5. Conclusion & Analysis
6. Reference
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1. Introduction
1.1 Building Description
Property: Global Gateway (HK) ()
Type: Office / Warehouse
Location: Tsuen Wan, New Territories
No. of Storey: 27 nos.
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1.2Busbar System
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Rating Busbar No. Location Purpose
3200A LVH-ESS From G/F SWBD 7B to Cark Park Level2 SWBD 4, 5 & 6
Essential Power
1600A SW7-
MSB-7A
From G/F SWBD 7B to 13/F SWBD
MSB-7A
Normal Power
1600A SW7-
MSB-7B
From G/F SWBD 7B to 13/F SWBD
MSB-7B
Normal Power
1250A MSB-AC7 From G/F SWBD 7B to 27/F SWBD
MSB-AC7B
A/C Plant
1.2Busbar System
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2. Problem
The voltage drop phase L1 of MSB-7B busbars route is
abnormally higher than the other 2 phases.
Busbar
No.
Length
(m)
Voltage in supply side (volt) Voltage in load side (volt)
L1-N L2-N L3-N L1-N L2-N L3-N
SW7-
MSB7A
202 222 222 222 217 217 217
SW7-MSB7B
260 219 220 219 211.5 217 215
MSB-AC7 311 219 219 221 216 216 218
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2. Problem
Length(m)
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1. High contact resistance at the concerned busway joints due to
insufficient torque tightening.
2. High resistance at the concerned flat elbow bends due to
improper welding or materials being supplied. Based on the
drawing, please note the concerned area have quite a few
numbers of flat elbow bends.
3. Low conductivity of the conductor due to its impuritymaterials supplied.
4. The run is exceptionally long (260m) which created higher
inductance.
3. Probability factor affect
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4. Improvement
4.1 Torque test for the joint bolts
4.2 Ductor test for busbar
4.3 Adding the transposition unit
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4. Improvement
4.1 Torque test for the joint bolts
Check the tightening torque of bolts not fitted with torquenuts. For bolts fitted with torque nuts, check the head has
broken-off.
Check the bolt length exceeding the nut (10mm): some bolts
should be removed and then put back, but left un-tightened.
Mark each tightened nut using indelible varnish. As well as a
means of self-inspection to ensure correct tightening torque,
it also allows any untightening to be identified.
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4. Improvement
4.1 Torque test on the joint bolts
All joint bolts of busbar were fixed as per the method statement of
manufacturer.
Bolt Tightening torque Bolt Tightening torque
HM 16 16 mdaN HM 12 7 mdaN
HM 14 12 mdaN HM 10 5 mdaN
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4. Improvement
4.2 Ductor test for busbar
Use the digital low resistanceohmmeter
To test the busbar joint condition
The results are listed as below:
Resistance Test in m
Busbar no. Rating N-L3 N-L2 N-L1 L3-L2 L3-L1 L2-L1
SW7-MSB7B 2000A 10.859 10.861 10.835 10.882 10.854 10.858
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4.3 Adding the transposition unit
Adding the transposition unit
To minimize the inductance effect
3 nos. of phase transposition units are to be added
4. Improvement
Each busbar enclosure contains 3 phases and all 3 phases are in
the same length.
It was identified that there are no abnormality with the resistance
values of the 3 live phases + neutral phase.
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4. Improvement
1
2
3
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4. Improvement
N
L3
L2
L1
N
L2
L1
L3
N
L2
L1
L3
N
L1
L3
L2
N
L1
L3
L2
L3
L2
L1
Section 1 Section 3Section 2
4.3 Adding the transposition unit
Equal intervals per each busbar run.
Balance the voltage drop
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4. Improvement
4.3 Adding the transposition unit
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4. Improvement
4.3 Adding the transposition unit
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4.3 Adding the transposition unit
4. Improvement
The anticipated voltage drop around= (219-211.5)+(220-217)+(219-215)/3
= 4.8 V
% of Volt drop = (4.8/220)X100%
= 2.2% < 4%
The voltage drop is complied with the EMSD requirement (between the
supply terminals and the fixed current using equipment does not exceed
4% of the nominal voltage of the supply.
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5.Conclusion & Analysis
R
XL
XC
))(( 22CL
XXRZ !Total Impedance:
XL
XC
R
))sin(( 22CL
XXRZ ! U
Total Impedance, Z increased
Then total power loss will increased
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5.Conclusion & Analysis
A
B
C
b
aa
c
L/3 L/3 L/3
A
B
C
710]log3log22
1[ !
b
chj
r
bcL
A
710]log3log22
1[ !
c
ahj
r
caL
B
710]log3log22
1[ !
a
bhj
r
abL
C
Individual Inductance [A/metre length]:
)(3
1C
TLLLL !
metreHr
abchLT /10)log2
2
1( 7
3
!
Total Inductance (Transpose at equal intervals):
Total power loss
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To avoid this problem, the transposition unit
shall be installed in construction period as per
the ASD requirement.
Use the non-segtegated bus ducts.
5.Conclusion & Analysis
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6.Reference
Design Fundamentals for Low-Voltage Distribution and control
Frank W. Kussy/Jack L. Warren
ASD Electrical installation General Specification
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ENDEND
&&
THANK YOU!THANK YOU!