IBTM601a Presentation v5

8/8/2019 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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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


Equal intervals per each busbar run.

Balance the voltage drop


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4. Improvement



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4. Improvement



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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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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.



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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!

IBTM601a Presentation v5

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