Analysis of existing distribution system and feasibility study on underground distribution system of BaidamFeeder, Lakeside Pokhara

1. ANALYSIS OF EXISTING DISTRIBUTION LINE AND
FEASIBILITY STUDY ON UNDERGROUND CABLE SYSTEM,
LAKESIDE POKHARA
Bishal Rimal(BEL-070-213)
Himal Chaulagain(BEL-070-218)
Manoj Sah(BEL-070-224)
Paras Subedi(BEL-070-228)
Project Supervisor: Er.Rajendra Dhakal

2. Electric power distribution is the final stage in the delivery of
electric power; it carries electricity from the transmission system to
individual consumers.
Radial Distribution System
Ring Main Distribution System
Network Distribution System
Load flow study is numerical analysis of the flow of electric power
in an any system. Load flow studies basically comprises of the
determination of
Voltage and power angle
Active Power
Reactive Power
losses
INTRODUCTION

3. An Overhead power line is a structure used in electric power
transmission and distribution to transmit electrical energy along
large distances. It consists of one or more conductors
suspended by towers or poles
Underground cables transmit power across densely populated
or areas where land is costly or environmentally sensitive
load forecasting Load forecasting is a technique used by
energy providing companies to predict the energy needed to
meet the demand and supply equilibrium

4. ETAP
Platform which gives the solution for Generation,
Transmission, Distribution, Industrial,
Transportation, and Low-Voltage Power Systems
Google Earth
Geobrowser that accesses satellite and aerial
imagery, ocean bathymetry, and other geographic
data over the internet to represent the Earth as a
three-dimensional globe
Software used

5.  OSMTracker for Android
This application allows us to record our
track, save waypoints(geotagging).
The output of our recording can be export
into GPX file format and we can open it
through Google Earth.

6. To analyse the peak power demand ,losses and voltage drop on
the feeder.
To analyse the reliability of the feeder.
OBJECTIVE

7. To forecast the load demand for 15 years.
To analyse the feasibility in replacing the overhead
distribution line by underground cable
Economic estimation of underground system

9.  Data collection
NEA
Private transformer load record
No. of transformer
Single line diagram of Baidam feeder
Collection of Peak load data of past 8 fiscal years
METHODOLOGY
BAIDAM FEEDER Private NEA
Number of transformer 35 42

11.  Daily load log sheet of Baidam feeder 28April
2017
0
500
1000
1500
2000
2500
3000
3500
4000
4500 1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
9:00
10:00
11:00
12:00
13:00
14:00
15:00
16:00
17:00
17:30
18:00
18:30
19:00
19:30
20:00
20:30
21:00
22:00
23:00
24:00:00
Daily load curve
Kw

12. Field Survey
 With the help of OSMTracker for Android (for obtaining GPS
coordinate of transformer location) and Google Earth (for plotting
the transformer and its line route distance measurement)
OSMTRACKER
GPX GOOGLE EARTH Plot the location on map
Transmission lengthETAP

14. ETAP Simulation
Following assumption are made for the simplicity of analysis.
All peak load occurs at the same time for all transformer.
All three phase are balanced.
Power factor: 0.85
All transformers are solidly grounded.
No private consumer use reactive power compensator.

15. We simulate the existing distribution system on ETAP
under three conditions:
Simulation of existing system using data of 28 April
2017
Simulation of existing system using annual peak load
of fiscal year 73-74.
Simulation of existing system replacing overhead line
by underground cable beyond Jarebar using annual
peak load of fiscal year 73-74

16. Load Forecasting
Available Data: 66/67 to 72/73- During Load Shedding
73-74-During No Load Shedding
Trend analysis method.
From that peak load with load shedding data we forecast
the peak load of fiscal year 73/74 assuming load shedding
Relative percentage peak load variation between load
shedding period and without load shedding period is
13.95% using peak load of fiscal year 73/74

18. 1. Simulation of existing system using data of 28 April
2017
Peak load: 3848KW @power factor 0.85
Peak KVA: 4528KVA
Demand factor: 0.47
Average Private Transformer loading: 18%
Average NEA transformer loading: 71%
Total Active power loss: 294.5KW
Percentage active power loss: 7.65%
Total reactive power loss: 383.5 KVAR
Percentage voltage drop: 11.46%
End terminal voltage: 9.74KV
RESULT AND ANALYSIS

19. 2.Simulation of existing system using annual peak
load of fiscal year 73-74
Peak load: 6397KW @power factor 0.85
Peak KVA: 7526KVA
Demand factor: 0.78
Average Private Transformer loading: 50%
Average NEA transformer loading: 100%
Total Active power loss: 860.2KW
Percentage active power loss: 13.45%
Total reactive power loss: 1073.9 KVar
Percentage voltage drop: 20.75%
End terminal voltage: 8.8KV

20. 3.Simulation using underground cable beyond
Jarebar
Peak load: 6397KW @power factor 0.85
Peak KVA: 7526KVA
Demand factor: 0.78
Average Private Transformer loading: 50%
Average NEA transformer loading: 100%
Total Active power loss: 788.6KW
Percentage active power loss: 12.32%
Total reactive power loss: 1005.4 KVAR
Percentage voltage drop: 17.96%
End terminal voltage: 9.0244KV

21. Losses
 Transformers and power lines are major source of Technical losses
in power distribution system.
 Unbalanced loading is another factor which results to losses in
electric distribution line
0
200
400
600
800
1000
1200
Active power loss Reactive power
loss
Chart Title
Existing system
using annual peak
load of fiscal year 73-
74
Underground cable
beyond Jarebar
Figure: Comparison of losses

22. Reduction of peak loss=71.6KW
LF=0.441
LLF=0.3LF+0.7LF2 = 0.268
Reduction on Average power loss=LLF*peak power loss
=19.18 KW
Average annual energy saving= 19.18*365*24
=168094 KWhr
Less spacing between the conductors the cables have much
capacitance, so draw higher charging current. Thus the line
capacitance compensates the reactive power demand and hence
reactive power demand decreases.
Reduction in total reactive power loss = 1073.9-1005.4
=68.23KVAR.

23. Voltage Drop
Lower voltage drop in underground system than overhead
system due to lower inductance because of smaller spacing
between conductor cable in underground distribution system
20.75
17.96
Existing system using annual peak load
of fiscal year 73-74
Underground cable beyond Jrebar
Percentage voltage drop
Also the surge voltage on the
underground system is
smoothed down as surge energy
is absorbed by the sheath
Voltage drop O/H = 20.75%
Voltage drop U/G = 17.96%

24. Reliability indices
Reliability
Indices
Overhead Distribution
System
Underground
Distribution System
SAIFI 4.9039 f /customer. yr 4.4499 f / customer.yr
SAIDI 320.82 hr/customer. yr 322.31 hr/customer.yr
CAIDI 65.423 hr / customer
interruption
72.429 hr / customer
interruption
ASAI 0.9634 pu 0.9632 pu

25. Load forecast
Using exponential model , MAPE= 3.32%
Load at (n) number of year = 4.136*exp(0.0526*number of year)
(considering 66/67 as base year)
0
2
4
6
8
10
12
14
16
KW
Peak load MW
during load
shedding
forecasted Peak
load without
Loadshedding MW
Figure: Forecasted load vs fiscal year

26. S.N. Year
Peak load MW during load
shedding(MW)
Peak load without Load shedding(
MW)
1 66-67 5.263 4.528
2 67-68 5.393 4.640
3 68-69 5.441 4.681
4 69-70 5.62 4.836
5 70-71 6.138 5.281
6 71-72 6.964 5.992
7 72-73 7.012 6.033
8 73-74 7.289 6.397
9 74-75 - 6.640
10 75-76 - 6.998
11 76-77 - 7.376
12 77-78 - 7.775
13 78-79 - 8.195
14 79-80 - 8.6376
15 80-81 - 9.1041
16 81-82 - 9.5958
17 82-83 - 10.114
18 83-84 - 10.660
19 84-85 - 11.236
20 86-87 - 11.842
21 87-88 - 12.482
22 88-89 - 13.156

27. Load Forecast
The peak demand after 15 years will be 13.867 MW.
Generally as according to various research papers it has been
concluded that 11KV system can economically carry sufficient
current to handle about 10MVA load at reasonable distance
probably 15 Km from primary substation.
Thus, the present lines couldn’t supply the power reliably and
efficiently in near future
Thus if peak load continues to increases in this similar trend, our
present system can’t handle its load reliably after 2079-80.

28.  Selection of cable
 After 2079-80 the current feeder is unable for a reliable power
supply in the service area
So, for FY 2079-80
Annual peak load=8.5MW
System voltage=11KV
Peak value of current through the cable =
8500
3∗11∗0.85
=
524.86A
 From cable selection table, For 525A current for duct bank, 630mm2
single core AL XLPE 11KV cable with ampacity 550A is selected
for straight run of feeder beyond Jarebar i.e. 4.29km
FEASIBILITY STUDY ON UNDER GROUND
CABLE SYSTEM

29.  For long and heavily loaded braches we select the 3 core XLPE
cable of size 185mm2 with ampacity 290A for the approximate
distance of 6.65km
 For smaller branching, 3 core XLPE cable of size 70mm2 with
ampacity 165A is selected for approximate distance of 2.61km
 Cable laying method
 Direct laying
 Draw-in system
 Solid system
According to our requirement in the service area considering the
reliability and economy, draw in system is preferred

30.  Duct Specification
 Type
i. Stone ware pipes
ii. GI pipes
iii. Cast Iron Pipe
iv. Spun Reinforced Concrete Pipe
v. HDPP or PVC pipe
Among these HDPP pipes are selected for undergrounding due to its
low initial cost, lighter weight, longer lifespan, low maintenance cost
and faster assembly
Size and Configuration
i. For a single cable duct diameter shouldn’t less than 10cm
ii. For a more than one cable duct diameter shouldn’t less than
15cm
Following configuration can be used for our project

31. Figure: Cross-sectional view of duct configuration

32.  Manholes and Joint
 For clear working space for performing necessary maintenance
manhole size be 6ft * 3ft
 Joint should provide the required electrical connection as well as the
mechanical support
Figure: Manhole Figure: Typical cable joint

33.  Protection against Fault
 Pad-mounted fused switches
 Pad-mounted vacuum fault interrupter
 Pad-mounted breakers or reclosure
 Cable end capping
 Cold shrink cap
 Heat shrink cap
 Denso seal

34. Cable Installation
Winch pulling
Laying cable from a moving drum trailer
Pulling in by hand
Bond pulling
Winch pulling or laying of
cable direct from a moving
cable drum trailer is to be
preferred because it is less
arduous with fewer people

35.  Economic Calculation
 Approximate cost for undergrounding the portion of service region
of Baidam feeder (beyond Jarebar) is summarized below:
S.N Parameter Cost (Rs.)
1 Cable Cost 5,72,82,400
2 Duct Cost 4,82,00,000
3 Manhole Construction
Cost
27,20,000
4 Excavation Cost 9,45,520
5 Installation Cost 3,54,570
6 Jointing Accessories Cost 4,40,630
7 Protection System Cost 23,68,800
Total 11,23,11,920

36. The excavation of cable route in already settled area is
difficult, resulting in more expense of economy
The problem for traffic during the excavation of cable route is
very significant. So, we might have to compromise our
working schedule and local sound pollution during working
hours
Dusts produced after excavation, can cause the air pollution in
the city. Thus, the project must be completed within short
period of time
Water pipes and drainage system are the vital components of
city thus must be considered throughout the excavation period
The routing of the cable during crossing of the main road
Possible Obstacles

37. After simulating the present system under two condition, we
conclude that in underground system the active power loss is
reduced thereby reducing annual energy lost cost
The present value of peak load is 6.397MW. If this trend
normally continues to increase, the present system is not capable
to carry the power economically, after fiscal year 2079-80 due to
economic limitation of 11kv line
Though the initial cost of installation of underground cable
distribution system is higher than that for overhead system, the
operating cost and the maintenance cost for underground
distribution is much lower than that for the overhead system
CONCLUSION

38. In terms of rate of interruption of supply, we can conclude that
underground system is more reliable than overhead system
because there is very less chance of affecting the system by
lightning, wind, storm and ice
Since all the cables and other accessories are buried under the
ground level, so, the underground cable system provides an
adequate level of safety to the public and tourists, and helps in
maintaining the natural beauty
Summarizing, we concluded that underground distribution
system provides a higher level of managerial and safety
benefits than the overhead distribution system

39. Following recommendation can be made to reduce losses in present
context
 Loading on each phase should be balanced as far as possible
 Most of the private transformers in the feeder run at low loading
condition causing high No load loss .So transformer of proper size
should be provided to the private consumer considering the future
possible load growth
 Installation of shunt capacitors for improvement of power factor in
the proper places.
 Good workmanship during the repair and maintenance is also a
includable factor to reduce the minor non technical losses
 For reliable performance after fiscal year 2079-80, the feeder must
be divided into two parts
RECOMMENDATION

40. [1] (Nagrath, 2014)D.P Kothari and I.J Nagrath “Power System
Engineering”, second edition
[2 (Gupta, 2012)] J.B Gupta “Electrical Installation Estimating and
Costing”, ninth edition
[3]http://www.theiet.org/forums/forum/messageview.cfm?catid=205&th
readid=62888
[4] Navaraj Poudel, Sumit Adhikari, Bhupendra Shaud, and Manoj
Kumar Yadav, “Comparative study of different feeders in Kudhar
substation” BE final year Project, IOE Paschimanchal, Campus.
[5] http://ieeexplore.ieee.org/abstract/document/667402/
[6] http://www.thestate.com/opinion/letters-to-the-
editor/article41203599.html
[7] http://www.jainvidyut.com/pdf/raychem-pricelist-2013.pdf
References

41. THANK YOU!!!