IMPROVING VOLTAGE PROFILE AND REDUCING LOSS IN
THE HANOI POWER DISTRIBUTION SYSTEM
CONSIDERING DISTRIBUTED GENERATIONS AND CAPACITOR
BANKS
CẢI THIỆN CHẤT LƯỢNG ĐIỆN ÁP VÀ GIẢM TỔN THẤT TRONG
HỆ THỐNG LƯỚI PHÂN PHỐI TP. HÀ NỘI
CÓ XEM XÉT ĐẾN NGUỒN PHÂN TÁN VÀ BỘ TỤ
A thesis submitted in partial fulfillment of the requirements for the
Degree of Master of Engineering in
Energy
Asian Institute of Technology
School of Environment, Resources and Development
ii
Acknowledgements
The author would like to express his deepest gratitude to his advisor,
the chairman of the thesis examination committee, Dr. Mithulananthan.
N.
The author would also like to thank Dr. Weerakorn. O and Prof. Sam R.
Shretha for their kindness in serving as members of examination
committee and for their valuable suggestions and advice throughout
this study.
The author wishes to convey his thank to the Electricity of Vietnam for
generously granting the scholarship so that he could pursue this
valuable master degree.
The author also thanks Ha Noi Power Company (HPC) for providing
him the opportunity to pursue this valuable master degree, to the staff
and officers of HPC, for their assistance during the data collection
phase.
Many thanks are also sending to the faculty and staff members of
Energy Program, especially to Mr. Pukar Mahat, for their help during
the study.

CAPO – Optimal Capacitor placement
DG – Distributed Generation
EVN – Electricity of Viet Nam
E2 – Long Bien distribution substation
HPC – Ha Noi Power Company
kWh – kilowatt hour
kW – kilowatt
kV, V – kilovolt, volt
kVAr – kilovar
kVA – kilovolt ampe
km – kilometer
MW – megawatt
PSS/ADEPT – Power System Simulator – Advance Distribution Engineering
Productivity Tool
pf – power factor
pu – per unit
v
Tables of Contents
Chapter Title
Page
Title i
Acknowledgements ii
Abstract iii
List of abbreviations iv
Tables of Contents v
List of tables ix
1. Introduction 1
1. Mở đầu Error! Bookmark not defined.
1.1 Background 1
1.2 Statement of problem 2

4.2 Optimal DG placement when DG Supply Real Power Only 25
4.3 Optimal DG placement when DG Supply Reactive Power Only 27
4.4 Optimal DG placement when DG supply P and consumes Q 27
5. Methodology 29
5. Phương pháp luận Error! Bookmark not defined.
5.1 Overview of methodology 29
5.2 Optimal DG placement to reduce system real power loss 30
Software Tools 31
5.3 Optimal Capacitor Placement Using PSS/ADEPT Application 33
5.3.1 About the PSS/ADEPT Software 33
5.3.2 Analyze Network in PSS/ADEPT 33
5.3.3 Load Flow Analysis in PSS/ADEPT 34
5.3.4 Calculating Capacitor Placement 35
5.4 System data 37
6. Results and conclusions 38
6.1 Optimal Distributed Generation 38
6.1.1 Results of Radial Feeder 983-E2 38
1. Type 1: DG supply real power only: 38
2. Type 2: DG supply real power and consume reactive power: 40
6.1.2 Results of Radial Feeder 979-E2 42
1. Type 1: DG supply real power only: 42
2. Type 2: DG supply real power and consume reactive power: 45
6.2 Optimal Capacitor Placement 47
6.2.1 Results of Radial Feeder 983-E2 48
1. Results of Load flow analysis 48
2. Results of CAPO 48
6.2.2 Results of Radial Feeder 979-E2 50
1. Results of Load flow analysis 50
2. Results of CAPO 51
7. Conclusions 54

45
Figure 6-10: Optimal DG size at each bus type 2 case 979-E2 46
Figure 6-11: Real power loss when DG installed at each bus with optial size
type 2 case 979-E2 46
Figure 6-12: Voltage profile before and after DG installed type 2 case 979-E2
47
Figure 6-13: Voltage profile of feeder 983E2 before capacitor placement -
plotted by PSS/ADEPT 48
Figure 6-14: Voltage profile before and after capacitors placement by CAPO
50
Figure 6-15: Voltage profile of feeder 979E2 before capacitor placement 51
viii
Figure 6-16: Voltage profile of feeder 979E2 before and after capacitor
placement by CAPO 52
ix
List of tables
Table Title Page
Table 2-1: Available capacities of DG for various technologies 11
Table 6-1: Ranking of buses for loss reduction type 1 case 983-E2 ( Appendix
B) 39
Table 6-2: Ranking of buses for loss reduction type 1 case 983-E2 (Appendix
B) 41
Table 6-3: Ranking of bus for loss redution type 1 case 979-E2 44
Table 6-4: Ranking of bus for loss redution type 2 case 979-E2 46
Table 6-5: Compare the results of case 983-E2 52
Table 6-6: Compare the results of case 979-E2 52
1
1. Introduction
1.1 Background
Electric power distribution system engineering has been designed to deal with

sizes and the locations to take part in the distribution networks in order to
improve voltage profile and minimize loss. The second part uses PSS/ADEPT
software to find the optimal capacitor banks placement
2
1.2 Statement of problem
Hanoi Power Company (HPC) is a utility that serves almost 450,000
customers in seven urban districts and seven rural districts of Ha Noi. In the
recent years, HPC had implemented a lot of management methods and
upgrading projects to reduce voltage drop, technical and non-technical power
loss However, regardless of all the attempts made, losses are running at
unacceptable percentage, about 11%.
At presently, the growth of energy consumption in Ha Noi is very high. In
order to meet customer demand, Ha Noi distribution network needs to be
planned to improve quantity and quality of electricity supply to meet social
and economical development of Ha Noi in coming years.
Two effective options to reduce power loss and voltage drops are using shunt
capacitors to compensate reactive power in primary feeders and using DG as
an alternative. Now there is a few shunt capacitors installed in primary
feeders. On the other hand, distributed generation is a new term with Viet
Nam, so there is no DG installed in HPC network at that time.
For a long time, capacitor bank is contributed in the whole distribution system
operation. However, with number of benefits that installation of DGs in the
distribution system can bring [see 2.3.2], the DG alternative becomes very
attractive to achieve the objectives.
In recent years, many researches and studies show that DGs provide various
benefits to the system when they are properly planed and operated. On the
other hand, improper placement and operation will degrade the power quality,
reliability and control of the power system, also may lead to even higher loss.
Thus, feasibility studying about DGs should be also carried out as good
options in planning period.

1- Existing transmission and distribution system in Hanoi Power
Company will be used in the study
2- This study is implemented in one of distribution substation of Hanoi
Power distribution network.
3- Only power balance constraint is considered.
4- DG in this study implies small size generation at the distribution
level and these DGs must have ability to generate reactive power.
1.5 Expected results
This thesis studies the methods how to reduce power loss and voltage drop in
distribution system by compensating reactive power using shunt capacitor
banks and DGs. The expected results are the followings:
1. Examination of one existing distribution substation loss and capabilities
of reduction in power loss as well as improvement of voltage profile.
2. Desirable locations and sizes of DGs.
3. Desirable locations and sizes of shunt capacitors.
4. Expected loss reduction, voltage profile improvement.
With the results will be obtained, the author expect that HPC will put these
methods in operation to reduce power loss and to improve voltage profile.
At present, the author viewpoint is that the optimal capacitor placement
method is more feasible than the optimal DG placement method. Further, the
4
author expects that the second method will be applied in HPC network in near
future.
5
2. Literature review
Reducing voltage drop and power loss is one of the biggest challenges in
electric power utility of developing countries. The electricity demand is
growing sharply. As a result of this, a poor voltage profile as well as higher
loss can be reality if no proper measures are put in placed. While the utilities
are not having sufficient funds for expansion their grid and source, it is

of them fall under non-technical losses. The reduction in system loss can
6
result in substantial saving in energy as well as increase in the power capacity
supply.
Generally, the loss in distribution system is higher in comparing with
transmission system. According to EVN report, in 2004, the shares of loss are
technical distribution loss 61%, non-technical loss 5%, and transmission loss
34%.
Traditionally, there are number of solutions to reduce distribution system
losses, such as network reconfiguration, load balancing, introduction of higher
voltage level, reconductoring, and capacitor installation, etc. Among these,
capacitor placement is considered as one of the most economical option.
Nearly years, distributed generation has been considered as the good
alternative with various benefits.
2.2 Distributed Generation
2.2.1 Development of Applications DGs
Trend in supplying electricity, for few decades now, is mainly through the
hierarchical systems include generation, transmission, and distribution
system. In recent year, with the development of new technologies, many types
of Distribution Generation are successfully applied, mainly in developed
countries.
Although having lot of challenges, more and more DGs are coming to the
market basically with electricity liberalization. This is clearly indicated by
increasing share of DG in electricity market. In the United State, for example,
DG resources or on-site generation cover more than 30% of installed capacity.
This trend is likely to accelerate as deregulation of electric power markets is
materialized. According to International Council on Large Electric System
(CIGRE) report, contribution of DGs in Denmark and the Netherlands has
reached 37% and 40% respectively [29]. Electric Power Research Institute’s
(EPRI) study forecasts that 25% of new generation will be distributed by 2010

electrical codes are hampering the development of the DGs and these barriers
are expected to be overcome by the restructuring of electricity industry [28].
DG’s penetration in power system is increasing, and in the future power
system might look like the one shown in Figure 2.2 (Source: Distributed
Utility Associates).
2.2.2 Benefits of DG
• Development in distributed generation technologies, constraints on
construction of new transmission lines, increasing customer demand for
highly reliable electricity, electricity market liberalization, and concern
about climate change [26].
• It provides a relatively low capital cost compared to its central counterpart
in response to incremental increases in power demand and avoid
transmission and distribution (T&D) capacity upgrades by locating power
where it is most needed [36].
• DG can defer capital cost of new transmission and distribution lines, reduce
transmission and distribution line loss, and improve power quality and
system reliability [32].
• DG can provide standby power during interruption and can significantly
increase the efficiency of energy utilization and thus may reduce global
emissions at lower costs [38], [39].
• It can result in peak shaving helping the energy supplier to reduce the cost
of generation and also provide ancillary service [38], [39].
8
• DG may level the load curve, improve the voltage profile across the feeder
and reduce the loading of the branches [40].
• Central generating companies can reduce load on their transmission
equipment, provide local voltage support and increase economical benefits
with DG [41].
• Government can use them to introduce competition in the electricity supply
market and thus create price reduction [41].

− Compact, easy to install, easy to repair.
− Lower capital cost and low electricity cost compared to any other DG
technologies
* Disadvantages:
− Not a quietest of DG, they require considerable muffling, which reduce
output and fuel efficiency.
− Fuel efficiency rather low compared to some other DG types
b Reciprocating Engines
Reciprocating engines are the most widely used type of power source for
distributed generators. They use diesel or natural gas as their fuel. Almost all
engines used for power generation are four-stroke and operate in four cycles.
10
* Advantages
− Low-cost manufacturing base and simple maintenance needs.
− Quick start-time and can be used for peak load shaving.
* Disadvantages
− Exhaust emissions, noise and vibration.
− Power quality is not as high as in inverter-based technologies such as
fuel cells and micro-turbines.
c Photovoltaic
The basic unit of PV is a cell that may be square or round in shape, made of
doped silicon crystal. Cells are connected to form a module or panel and
modules are connected to form an array to generate the required power. Cells
absorb solar energy from the sunlight, where the light photons force cell
electrons to flow, and convert it to dc electricity. Normally an array, cells
connected in series, provides 12V to charge batteries.
* Advantages:
− No fuel and maintenance costs.
− No pollution.
− Extremely reliable and durable.

from chemical energy through electrochemical processes. It provides clean
power and heat for several applications by using gaseous and liquid fuels.
Fuel cell capacities vary from kW to MW for portable and stationary units,
respectively. There are different types depending on the electrolyte used such
as proton exchange membrane or polymer electrolyte membrane fuel cell
(PEMFC), alkaline fuel cell (AFC), direct methanol fuel cell (DMFC),
phosphoric acid fuel cell (PAFC), molten carbonate fuel cell (MCFC) and
solid oxide fuel cell (SOFC). Like the reciprocating engines, they can regulate
the voltage of the bus at which they are connected.
* Advantages:
− Higher efficiency compared to conventional generations (about 60%)
− Low noise and pollution level
* Disadvantages
− Need power electronic interface to regulate the output voltage.
2.2.4 Standard Sizes of Distributed Generation on Market
The typical available sizes per module of DG on the market in [32] will help
system planners to select the correct size that they need. Table 3.1 shows the
range of capacity for DG of different technologies.
Table 0-1: Available capacities of DG for various technologies
N
o
Technology
Typical available size per
module
1.
Internal combustion engines
5 kW -10 MW
2.
Combustion turbines
1 -250 MW

12.
Fuel cells, molten carbonate
250 kW – 2 MW
13.
Fuel cells, proton exchange
1 kW – 250 kW
14.
Fuel cells, solid oxide
250 kW – 5 MW
15.
Geothermal
5 – 100 MW
16.
Ocean energy
100 kW – 1 MW
17.
Sterling engine
2 – 10 kW
18.
Battery storage
500 kW -5 MW
2.3 Distribution Power Flow Algorithms
In order to analysis DG in the distribution system, the first step is to run a
distribution load flow with DG. The results can be analyzed to see the
technical viability of a DG in the distribution system.
Load flow is very important in power system operation and planning as it
provides the picture of steady state operating condition. It is desirable to know
the system operating condition at different loading levels for efficient and
reliable operation of the power system. Many real time and planning
applications require an efficient and robust power flow algorithm. Newton

one feeding node. The method first converts the multiple-source mesh
network into an equivalent single-source radial type network by setting
dummy nodes for the break points at distributed generators and loop
connecting points. Then the traditional ladder network method can be applied
for the equivalent radial system. Following each of the iterations of the
equivalent radial system, the power injected at the break points must be
updated by an additional calculation through a reduced order impedance
matrix.
Salama et al. [58] have presented a very simple but robust method - the ladder
formula. Essentially, the ladder network method treats the radial system as
two basic element types: the network natural elements (impedance) and
voltage control current sources (system loads) at each load node. The forward
sweep is mainly a voltage drop calculation from the sending end to the far end
of a feeder or a lateral; and the backward sweep is primarily a current
summation based on the voltage updates from the far end of the feeder to the
sending end.
Berg et al.[59] presented a backward method which used a backward
procedure to update the equivalent impedance at the sending end. The main
idea of this method is to treat the load as constant impedance. So if the
equivalent impedance is convergent, the whole system convergence will be
reached. This method is very costly and quite sensitive to the system load
level and load distribution, as well as the system structures.
Baran et al.[60] presented a forward method. In this method, the sending end
voltage becomes the main concern of the system convergence. Voltage drop
and the information on system structure have been considered in the forward
sweep. The voltage-sensitive load current can be included in the system
model. However, this method still has disadvantages. Oriented from ladder
network concepts, the 'branch flow equations' are essentially solved by a
14
Newton-Raphson approach which makes this method complex and costly.

formulated the problem with some variations of the above objective function.
Some of the early works have not considered capacitor cost in the
formulation. Some others have included system capacity release and load
growth into the problem formulation.
GA is a well tool to use in optimal capacitor placement [12-14], [18-20] and it
is the fact that GA has been successfully applied to the capacitor placement
problem. In this method, the parameter sets (sizes and locations) are coded.
GA operation will select a population of the coded parameters with highest
15
level and perform a combination of mutation, crossover to generate the better
set of parameters.
A technique applying fuzzy set theory [21], [22] is also applied to solve the
problem. In this technique, voltage and power loss indices are modeled by
membership functions and a fuzzy expert system containing a set of heuristic
rules that performs the inference to determine a capacitor placement
suitability index of each node. Capacitor would be placed at the node with
highest suitability.
Based on all of the method above, many programs are developed to solve the
problem of optimal capacitor placement. Most of current commercial software
is using numerical programming method to solve the optimal capacitor
problem.
Among these, the PSS/ADEPT software written by Shaw Power Technologies
proved an efficient tool for optimal capacitor placement in distribution system
that considers both fixed and switched capacitors, as well as economics
concerns [24].
2.5 DG Placement Techniques
With more and more DGs coming into distribution system, it is always
desirable to place them properly. Proper placement will reduce distribution
system loss, also provide free available capacity for power transmission and
reduce equipment stress. By proper DG placement, we can defer investment

methodology aims to minimize the capital investment and operation cost of
distribution company along with payment made toward the loss reduction,
power generated and cost of the power purchased from the grid and it also
compares the cost of network expansion with the DG installation. This
technique sometimes gives the solutions which are not practical and hence
planner experience decisions are required.
A genetic algorithm (GA) based distribution generation placement technique
to reduce overall power loss in distribution system is presented in [65]. B-loss
coefficient is used to find the system loss. The technique uses Genetic
Algorithm Toolbox and both the optimal size and location can be found from
it. Three more genetic algorithm based method for determining the DG size
and location is presented in [79]. Another genetic algorithm based DG
placement technique is presented in [48]. This algorithm finds the optimal
size and place where we can install DG, so as to reduce the system loss. The
technique is used to solve the DG placement problem in medium voltage
distribution system. GA is suitable for multi-objective problem and gives near
optimal solution but it is computationally intensive and suffers from excessive
convergence time and premature convergence.