nepal substations and loads

POWER EVACUATION SYSTEM STUDY FOR SELECTED HYDROPOWER PROJECTS PROJECTS IN WESTERN NEPAL

DISSERTATION Submitted in partial fulfillment of the requirements of Master of Engineering in Electrical Power Engineering

Manohar Manohar Shrestha

Department of Electrical and Electronics Engineering

School of Engineering

Kathmandu University

December 2005

POWER EVACUATION SYSTEM STUDY FOR SELECTED HYDROPOWER PROJECTS IN WESTERN NEPAL

DISSERTATION Submitted in partial fulfillment of the requirements of Master of Engineering in Electrical Power Engineering

By:

Manohar Manohar Shrestha

Under supervision of:

Mr. Surya Prasad Adhikari Planning and Design Engineer Engineering Department Butwal Power Company Ltd. and

Mr. Lalt Bickram Rana Assistant Professor Department of Electrical and Electronics Engineering School of Engineering


Department of Electrical and Electronics Engineering

School of Engineering


December December 2005

ACKNOWLEDGEMENT

I would like to express sincere and profound gratitude to our Project Supervisors Mr. Surya Pd. Adhikari and Mr. Lalit B. Rana for helping me to complete this project with valuable guidance whenever I faced problem during the course of dissertation. I would also like to express my hearty thanks to Dr. Bhupendra Bimal Chhetri, HOD electronics and electrical department, KU, for providing necessary material and uninterrupted access to computer lab for project work. Special thanks go to Mr. D.D Joshi, M.D AutoCarto Pvt. Ltd. for providing relevant data required for the study and Er. Kiroj Shrestha, Western Grid Office, NEA for helping to get existing present data of Western Nepal from Western Central Office, NEA. NEA. At last, I am very much thankful to my classmates and colleagues whose sincere efforts have inspired me to be with them in the pursuit of academic goals.

ABSTRACT

Electricity Power Evacuation from small hydro power plant is emerging as challenge for the entire entrepreneur who wishes to enter in the field of hydro power sector. The increasing load demand and availability of power market around the clock in Nepal has evoke many capitalist to invest in hydro power sector. This thesis studies the present and will identify future power evacuation system performance in certain area of Lamjung district from different power plants Khudi (KHP) 3.5 MW, Lower Nyadi (LNHP), 4.5 MW and Lower Khudi (LKHP), 2 MW. The thesis studies existing and proposed power evacuation system and carries out detail study stu dy of an existing transmission line and conduct detail study of power evacuation systems from KHP, LNHP and LKHP. The thesis also studies the performance of distribution system for Lamjung district. The methodology adopted for carrying out evacuation study is based on following:

•

Collection of data regarding existing and proposed electrical system.

•

Preparation of program/software for technical and financial analysis of evacuation system

•

Identification of different transmission line alternatives and selection of best option.

•

Study performance performance of evacuation sys tem. tem.

•

Study performance of distribution system.

For studying power evacuation system transmission capacity, available transmission margin and transmission are taken into consideration. For distribution system performance study computer programs are developed. Spreadsheet for calculation of transmission line performance performance and Carl1.0 (Load flow software for radial distribution network) network) for studying distribution feeders has been updated.

TABLE OF CONTENTS GLOSSARY OF ABBREVIATIONS

i

LIST OF FIGURES FIGURES

ii

LIST OF TABLES

iii

CHAPTER 1

INTRODUCTION 1

1.1

General

1

1.2

Objectiv Objectivee

1

1.3

Backgrou Background nd

2

1.4

Performance Performance standard for Grid

2

CHAPTER 2

EXISTING ELECTRICAL SYSTEM IN STUDY AREA 4

2.1

Existing power plants in western Nepal

4

2.2

Under Study Small Hydro Power Plant in Western Nepal

4

2.3

Existing Existing Grid transmission system in western Nepal

5

2.4

Existing Electrical Network in Some District of Western Nepal.

6

CHAPTER 3

METHODOLOGY 11

3.1

Data Collection

11

3.2

Transmission line alternative

12

3.3

Available Transmission Capacity

13

3.4

Transmission Margin

13

3.5

Performance Performance of Transmission Transmission line

13

3.6

Distribution system planning

13

3.7

Spread Sheet Calculation for Conductor selection and Voltage [2]

14

3.8

Carl 1.0

18

3.9

Netbas Simulation

18

3.10

Evacuation System for KHP, LNHP and LKHP.

19

CHAPTER 4

RESULTS AND DISCUSSIONS DISCUSSION S 20

4.1

Existing Existing System Result

20

4.2

KHP Evacuation Evacuation System

25

4.3

Results of LNHP Evacuation Evacuati on System

33

4.4

KHP and LNHP Evacuation Evacuati on system

34

4.5

System with KHP, LNHP and LKHP

41

4.6

KHP, LNHP, LKHP and Chame substation

42

4.7

Load flow analysis of four feeders of Udipur S/S

43

CHAPTER 5

CONCLUSION AND RECOMMENDATION 45

REFERENCES

48

APPENDICES

Appendix

A:

Transmission line Design Procedur e

Appendix

B:

Load Flow Analysis in Electric Power distribution

Appendix

C:

SLD of Existing Electrical Network

Appendix

D:

Spread Sheet Results

Appendix

E:

Netbas Results

Appendix

F:

Carl1.0 Results

Appendix

G:

List All Power source and Cost

GLOSSARY OF ABBREVIATIONS Abbreviation INPS KHP LNHP LKHP NEA JHP BPC DOED SHPP WI VDC LEDCO ACSR USC S/S KSw/S USS DuSS AkSS DaSS

Full-Form Integrated Nepal Power System Khudi Hydro Power Lower Nyadi Hydro Power Plant Lower Khudi Hydro Power Plant Nepal Electricity Authority Jumdi Hydro Power Butwal Power Company Department of Electricity Department Small Hydro Power Project Winrock International Village Development Committee Lamjung Electricity Development Company Aluminum Conductor with Steel Reinforcement US Cent Substation Khudi Switching Station Udipur Substation Dumre Substation AnbuKhaireni Damauli Substation

First in Page

2 2 2 5 5 5 8 9 9 15 21 26 31 31 31 31

i

LIST OF FIGURES Figure No.

Caption

Page

2.1

5 MVA 33/11 kV Udipur Substation

10

3.1

Conductor optimization sheet using spreadsheet

17

4.1

Existing Electrical System of Lamjung District

20

4.2

Conductor selection for KHP evacuation

26

4.3

KHP evacuation system

27

4.4

Conductor optimization chart for LNHP only

34

4.5

Conductor and voltage chart for KHP and LNHP

36

4.6

KHP and LNHP evacuation system

37

4.7

KHP, NHP and LKHP evacuation system

42

4.8

Evacuation system with Chame load

43

ii

LIST OF TABLES Table No. 2.1 2.2 2.3 2.4 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 4.11 4.12 4.13 4.14 4.15 4.16 4.17 4.18 4.19 4.20 4.21 4.22 4.23 4.24 4.25 4.26 4.27 4.28 4.29 4.30 4.31 4.32 4.33 4.34 4.35

4.36

Caption Small Hydro Power Plants of Western Nepal SHP projects (1-10 MW) in Western Nepal Existing 132 kV Transmission Line of Western Nepal Feeder Status of 5 MVA, 33/11 kV Udipur S/S Full S/S load, Existing System 70% S/S load Existing System 50% S/S load Existing System 30% S/S load Existing System 10% S/S load Existing System 100% S/S load with 'Wolf' Existing System 80% S/S load with 'Wolf' Existing System 50% S/S load 'Wolf' Existing System Spread Sheet calculation for KHP evacuation system (0.9 km) Spread Sheet calculation for KHP evacuation system (14.9km) Full load, KHP evacuation System 70% load, KHP evacuation System 50% load, KHP evacuation System 30% load KHP evacuation System 10% load KHP evacuation System 100% load with 'Wolf' KHP evacuation System 50% load with 'Wolf' KHP evacuation System 100% S/S load, effect in existing system with KHP 70% S/S load, effect in existing system with KHP 50% S/S load, effect in existing system with KHP 30% S/S load, effect in existing system with KHP 10% S/S load, effect in existing system with KHP LNHP evacuation System LNHP and KHP 33 kV transmission line LNHP and KHP 66 kV transmission line 100% substation load, KHP and LNHP power evacuation 70% substation load, KHP and LNHP power evacuation 50% substation load, KHP and LNHP power evacuation 30% substation load, KHP and LNHP power evacuation 10% substation load, KHP and LNHP, power evacuation 100% load, effect in existing system, KHP &LNHP evacuation 70% load, effect in existing system, KHP &LNHP evacuation 50% load, effect in existing system, KHP &LNHP evacuation System Performance with KHP, LNHP and LKHP System performances with KHP, LNHP, LKHP and Chame Substation. Load flow result of four feeders of Udipur S/S.

Page 4 5 6 10 21 21 22 22 23 23 24 24 25 26 27 28 28 29 29 29 30 31 31 32 32 33 33 35 35 38 38 39 39 39 40 41 41 42

43 44

iii

Chapter 1 Introduction

CHAPTER 1

Introduction 1.1

General

Nepal, with its very difficult geographic structure, grid expansion to remote area has been very costly approach for rural electrification as well as to extend for small hydropower interconnection. Mainly these areas are planned based on the electricity distribution purposes. This thesis tries to develop the methodology especially for evacuating power from small hydropower plant in western Nepal by focusing on grid connection as well as local consumption using existing infrastructure. Nepal is divided into five development regions, 14 zones and 75 districts. Western development region is one of the development regions which comprises of three zones, Lumbini, Dhaulagiri and Gandaki and has 16 districts. The total generating capacity of interconnected power system of Nepal is 613.557 MW in total, of which about 556.5 MW is from Hydro Power Stations and 57 MW from Diesel and multi-fuel Power Stations. Obviously with the emerging scenario of increased power production, expansion of transmission and distribution system becomes essential. The project thesis, will study power evacuation options for different small hydropower plant by using the transmission line design program developed for this purpose and analyze new local market for energy consumption, necessary to evacuate growth in power production.

This thesis carries out evacuation study to incorporate the major changes in the power scenario of the western part of Nepal. A power Generation expansion study for different small hydropower plant is used for the transmission expansion studies. This report carries out evacuating system study for different selected hydropower plants that will be connected to grid in the coming years.

1.2

Objective

The major objectives of this thesis is to find out suitable power evacuation system for existing, under implementation and up coming projects analyzing existing transmission line. The project

1


also focuses on study of the selected existing distribution system in case of local power evacuation. The areas of work in this thesis consist of:

•

To select Suitable Small Hydro Power Plant in Western part of Nepal.

•

To get related data regarding existing electrical network of the area in the vicinity.

•

To find out transmission line alternatives.

•

Develop software in spread sheet in EXCEL to find out best transmission alternatives considering technical aspects.

•

To study system performance using Netbas Simulation.

•

To perform distribution system planning using distribution load flow software.

1.3

Background

In addition to government owned power development agencies (like NEA, MOW, WECS, and EDD) the private power development agency, Butwal Power Company is also actively participating in Generation, Transmission and Distribution of electrical power to INPS as well as local consumers. Butwal Power Company Limited (BPC) is the first private sector Power Company of Nepal. Today BPC is a leading Hydropower developer of the country. There are many small hydro power plants that have been identified in western part of Nepal which are under study. Each year few new hydro power generating potential sites are identified and undergo pre feasibility study followed by feasibility study. After completion of feasibility study power purchase agreement is signed with Nepal Electricity Authority (NEA). BPC is involved in developing 3.5 MW Khudi Hydro Power Plant (KHP), and studying feasibility study for 2 MW Lower Khudi (LKHP) and 2 MW Jhumdi (JHP) Hydro Power project. Power evacuation design is very necessary to get PPA signed and the design should be based on performance standard of grid.

1.4

Performance standard for Grid

Objective:

The objective of the Performance Code is to specify the minimum technical standards to ensure efficient and reliable operation of Grid [1].

2


Power Quality:

To ensure power quality as per NEA Grid Code standard voltage variation, frequency variation and transmission loss should be as follows: a.

Voltage Variation

The system operator shall ensure that the power supply voltage in the grid at major connection points during normal operating condition shall not deviate by more than +/- 10% of its normal value. b.

Frequency Variation

The system operator shall ensure that the fundamental frequency in the system is maintained between 48.75 Hz. and 51.25 Hz. i.e. +/- 2.5% of 50 Hz, which is the nominal value of fundamental frequency. c.

Transmission Loss

The grid owner shall ensure that the transmission loss does not exceed 4.5 % of the received energy.

1.5

Grid Connection Requirement

As per NEA Grid Code requirement, generator shall maintain Power Factor between 0.85 lagging and 0.95 leading [1].

3

Chapter 2. Existing Electrical System in study area

CHAPTER 2

Existing Electrical system in Study Area 2.1

Existing power plants in western Nepal

In western region there are three zones and sixteen districts. Electricity service is available in all districts through INPS grid (in eleven districts) and isolated small hydro power stations (in remaining 5 districts). In either case the electricity service is made available only in limited area. The total generation of western region is 260.49 MW and most of the generation plants of the region are situated in Gandaki Zone. The major hydropower plants in this region are 75 MW Marsyandi, 5.1 MW Andhikhola, 14.8 MW Modikhola, 144 MW Kaligandaki 'A', and 15 MW Gandak. The total installed capacity of major hydropower plants is 253.9 MW. There are twelve existing small hydro power plants of different sizes in western region with total installed capacity of 6590 kW [2]. Table 2.1: Small

SNo.

Zone

District

Hydro Power Plants of Western Nepal

Power Plant

Installed Capacity (kW)

Year of Commissioning

1 Gandaki Kaski Phewa 1088 2 Lumbini Rupandehi Tinau 1024 3 Dhaulagiri Baglung Baglung 200 4 Dhaulagiri Mustang Jomsom 240 5 Gandaki Syrrgja Syanja 80 6 Gandaki Kaski Seti 1500 7 Gandaki Manang Chame 45 8 Gandaki Manang Manang 80 9 Gandaki Gorkha Arughat 150 10 Dhaulagiri Myagdi Tatopani-I 1000 11 Dhaulagiri Myagdi Tatopani-I I 1000 12 Gandaki Lamjung Sangekhola 183 Note: SPC=Sange Power Company; source: System planning, NEA

2.2

1967 1978 1981 1983 1984 1985 1987 1988 1990 1991 1995 2002

Developer NEA NEA NEA NEA NEA NEA NEA NEA NEA NEA NEA SPC

Under Study Small Hydro Power Plant in Western Nepal

It is worth mentioning here that many Independent Power Producers (IPP) are showing strong interest in the development of small hydro power plant in Nepal. In western region only, there

4


are altogether 24 new small hydro power plants have been identified by private promoters. List of Identified S mall Hydro Power Plants identified by private promoters are tabulated below. Table2.2: Small

SN.

Project Name

Hydro Power Projects (1-10 MW) in Western Nepal

Project Location

Promoter

Installed Capacity (MW)

Bhimkhola

Baglung

Butwal Power Company

Bijayapur 1

Kaski

Bhagwati HP Development Company (P) Ltd

2

3

Daraudi

Gorkha

Shreerup Hydropower Pvt.Ltd.

5

DOED/SH PP DOED

4

Dharam Khola

Baglung

The Gorkha Hydropower P Ltd.

5

BPC

5

Dudh Khola

Manang

Swet Bhairb Pvt Ltd.

6

Dordi I

Lamjung

Shah Consult Pvt. Ltd.

7

Ghami Khola

Mustang

8

Jumdikhola

9

1 2

3.1

Informati on Source DOED

10

DOED

8

DOED

Cosmic Hydropower Pvt Ltd

2.5

DODE

Gulmi

Butwal Power Company Ltd.

2

DOED

Karuwa

Kaski

Jhyamolongma Hydropower Dev. Co.(P) Ltd.

6

DOED

10

Khudi

Lamjung

Lamjung Electricity Development Co. P Ltd

3.6

SHPP/WI

11

Kotre

Kaski

Machhapuchhre HP Development Company

3

SHPP/WI

12

Lower Myagdi

Myagd i

Nect Center Pvt.Ltd & Him Consult

5

DOED

Kaski

Arjun Prashad Paudy al

5

DOED

14

Madkyu Khola SHP Madi – 1 Hydro

15

Mardi Khola

Kaski

Gandaki hydro power Development P. Ltd.

16

Mardi Khola MD-1

Kaski

N/A

Lamjung

Baverian Hydropower Nepal P Ltd

4.9

SHPP/ WI

13

17 Nyadi II

Kaski

Annapurna Group P/ltd.

10 3 10

BPC DOED BPC

18

Pati Khola SHP

Parbat

Unified HP Pvt Ltd.

1.5

DOED

19

Paudi Khola SHP

Lamjung

N/A

1.5

DOED

20

Ridi Khola

Gulmi

Ridi Hydropower Development Co.Pvt.Ltd

1.8

DOED

21

Seti hydrop ower

Kaski

Seti Hydropower Development Co. (P) Ltd

10

22

Shardi Khola SHP

Kaski

Sarimati Deepal Poudel

1.7

DOED

Upper Dharam A SHP Upper Seti - 1

Baglung

Ghumte Hydropower Pvt Ltd

4.5

DOED

Kaski

Seti Hydropower Development Co. (P) Ltd

3

DOED

23 24

2.3

SHPP/ WI

Existing Grid transmission system in western Nepal

The available grid transmission voltage in western region is only 132 kV and sub transmission voltage is 33 kV. Grid transmission line is connected from east to west through Bardghat, Butwal and Shivapur areas and from north to south through Pokahara area. Bardghat is one of the major grid substations in south western part having power sources from Gandak, 15 MW power station and National Grid. Bardhaghat is connected to Bharatpur by 132 kV single

5


circuit transmission line in the east, with Butwal by 132 kV double circuit transmission line in the west and with Gandak power station by 132 kV double circuit transmission line. Butwal is another major junction of south-western part of the National Grid having power sources from National Grid, Andhi Khola, Tinau, Gandak, and Kali Gandaki 'A' power station. Butwal is connected with Bardhghat by 132 kV single circuit transmission line in the east, with Shivapur by 132 kV single circuit transmission line in the west and with Kali Gandaki 'A' power station by 132 kV double circuit transmission line. Shivapur (Chanauta) is also major junction of south-western part of the National Grid having power sources from INPS. This S/S is connected with Butwal S/S in the east and Lamahi S/S in the west by 132 kV single circuit transmission line. Pokhara S/S is connected to Bharatpur via Damauli in the south and is connected to Modi in the north. The existing transmission lines of western region are tabulated below. Table 2.3: Existing

Area

132 kV Transmission Line of Western Nepal

Voltage Level

Lamahi--Shivpur Shivpur--Butwal Butwal--Bardghat Bardghat--Gandak Bardghat--Bharatpur Bharatpur--Damauli Damauli--Pokhara Pokhara--Modi Bharatpur-- Marsyangdi Marsyangdi--Suichatar I Source: System Planning, NEA

132 132 132 132 132 132 132 132 132 132

No. of Circuit single single double single single single Single Single Single Single

Conductor Code

Line Length (km)

Bear Bear Bear Panther Panther Wolf Wolf Bear Duck Duck

51 61 43 14 70 39 46 37 25 83

Substations in Pokhara, Damauli, Bardghat, Butwal and Chanauta areas are the main power sources for western region [2].

2.4

Existing Electrical Network in Some Districts of Western Nepal.

To understand the existing electrical network up to distribution level in the western region data showing the present distribution status of some of the district is explained below. 1.

Palpa

In this district there are altogether 113,361 number of consumer including domestic, commercial, non-commercial, industrial and others. In this district electrification is done using

6


both 11 kV and 33 kV distribution systems. The total 11 kV distribution line length is 60 km and 33 kV distribution line lengths are 118 km. Most of the electrified areas are electrified using 33/0.4 kV, 99 numbers of distribution transformers of various sizes. In this district there is one area substation of capacity 6/8 MVA with three feeders East feede r (40 nos. of 11/0.4 kV transformers), Bazaar feeder (10 nos. of 11/0.4 transformers) and West feeder (30 nos. of 11/0.4 transformers). This substation receives power from Andhi Khola hydro power station and Butwal grid S/S. There are no existing power plants and also no new identified small power plants undergoing study.

2.

Parbat

As per NEA, in Parbat district the total number of consumers including domestic, industrial, commercial, noncommercial and others is 6,941. In Parbat distribution level voltage is 33 kV and 33/0.4 kV distribution transformer is used for power distribution to consumers. There is also 11 kV distribution line in this district and the line length is 26.39 km. The 33 kV distribution line lengths is 89.79 kV. There is no area substation in Parbat and no grid substation also. In case of power station, there are no existing power plants. Pati Khola SHP, 1.5 MW is the only small hydro power identified by Unified HP Pvt. Ltd. in this district which is now undergoing feasibility study.

3.

Syanja

According to the information obtained from Syanja Branch, NEA, total number of consumer including domestic, industrial, commercial, noncommercial and others is 11,200. In this district Private sector Company, BPC is involved in distributing electricity to about 14,000 numbers of consumers. Total Number of 33/0.4 kV Distribution transformer is 16. In this district also, distribution has been done in two voltage levels 33 kV and 11 kV. The total line length of 33 kV distribution line is 18.93 km and the total line length of 11 kV distribution line is 129.29 km. There are two are area substation under NEA, Badkhola, 33/11 kV, 1.5 MVA substation and Mirmi, 33/11 kV, 500 kVA substation. There is one existing power station, Andhi Khola, 5.1 MW, which has 5.3/33 kV substations with three feeders, Walling feeder with total connected load of 3265 kVA, Galyang feede r with total connected load of 3205 kVA

7


and NEA feeder, which is connected to Butwal grid substation passing through 200-kVA load. All these feeders feed load in 33 kV voltage level.

4.

Gulmi district

The Gulmi District is one of the districts of Lumbini Zone in Western Development Region. There are altogether 79 VDCs in this district. Tamghas is the district head quarter. Electrification in Gulmi district is very small compare to its size in terms of geography as well as demography. Only 24 VDCs out of 79 have been partially electrified from 33 kV sub transmission line joining 5 MW Andhikhola hydropower plant, 40 (1x10 and 1x30) MVA Butwal Grid substation and 12 MW Jhimruk hydropower plant. At present the total number of consumers is 8793 including industrial, commercial and others are enjoying benefits from electricity service in the district. Based on this, the electrification ratio of the district is only about 15%. Sub Transmission and Distribution Lines

There is no area substation in this district. 33 kV line network has been used to distribute electricity with 33/0.4 kV distribution transformers. The 33 kV line originating from Andhikhola enters the district at Aslewa, which is 17 km from source and joins 33 kV line of Butwal Grid substation at Baletaksar at a distance of about 77 km from the source. This 33 kV line further links the 33 kV subtransmission line from Jhimruk hydropower plant at Wangla in Arghakhanchi and Tamghas in Gulmi district, forming a looped network of 33 kV, which covers the load centers of both the districts. The total 33 kV line length in the district is approximately 158 km. All the existing 33/0.4 kV distribution tappings in the district have been shown in the single line diagram in Appendix C. This distribution network is consisting of fifty one (51) 33/0.4 kV distribution transformers of various capacities from 25 KVA to 100 KVA [3]. In this district, two upcoming small hydro power projects are identified and undergoing study. Jumdi hydro power (JHP), 2 MW is under feasibility study by Butwal Power Company (BPC) and Ridhi Khola SHP, 1.8 MW is also under feasibility study carrying out by Ridhi Hydro Power Development Company.

8


5.

Lamjung

Lamjung is one of the districts of Gandaki zone in western development region of Nepal. The existing electrical network in the Lamjung district is comparatively small. According to 8th power report, NEA, in Lamjung district only 24 VDCs out of 61 VDCs have partial access to electricity from a single 1.5 MVA, 33/11 kV substation at Udipur. About 4600 (year: 2001) numbers of consumer including industrial, commercial, and other have access to electricity in the district. This data shows that the electrification ratio of about 11% and the total energy consumption is about 1472 MWhr. (Year: 2001). One distinct electric power generating activity in the district is the 183 kW, small-scale hydropower plant, which is under operation at Sange (of Taghrin VDC) by a private company, LEDCO.

Source Substation In Lamjung there is only one 5 MVA, 11/33 kV area substation at Udipur. Source for this area substation is 132/33 kV Grid substation at Damauli which is 34.5 km from Udipur. In between Damauli Grid substation and Udipur substation there is another 5 MVA, 33/11 kV substation at Dumre from where 20 km long 33 kV transmission line is tapped directly to feed Udipur substation. Besisahar headquarter of Lamjung district and the area in the vicinity is electrified from four different outgoing feeders from Udipur substation. Small part of Tanahu district is also electrified from this substation. The four feeders are Besisahar, Okhari, Bhote Odar and Nayagaon.

Sub Transmission and Distribution Lines In Lamjung district the only sub transmission line is 20 km long Dumre-Udipur 33 kV overhead line constructed on wooden poles using ACSR conductor 65 sq. mm (equivalent copper area) “Dog”. In case of distribution lines, about 229 km of (including proposed 128 km) 11 kV line is distributing electricity up to consumer premises. The conductor used in 11 kV distribution line are ACSR “Rabbit” and “Weasel”. There are 115 numbers of 11/0.4 kV distribution transformer of varying capacities from 25 kVA to 200 kVA including existing and proposed transformers on four outgoing feeders from Udipur substation. Four out of 105 transformers are located in Tanahu district. The existing electrical network in Lamjung district is presented in

9


Appendix C. The 11 kV outgoing feeder from Udipur S/S and total connected load in each feeder of this district is presented below [3].

Figure 2.1: 5 MVA, 33/11 Udipur Substation

Feeder status of 5MVA, 33/11 Udipur substation. Name of Feeders Total No. of Transformer Total kVA Besisahar Feeder 36 1400 Okhari Feeder 17 550 Bhote Odar Feeder 45 2125 Majhgau Feeder 17 575 Total Connected kVA 4650 Table2.4:

Power Plants

Khudi, KHP (3.5 MW) is undergoing construction in this district, and is expected to connect with the NEA Grid at Udipur substation. Lower Nyadi Hydro Power with installed capacity of 4.5 MW is upcoming hydropower which also gets access to grid through 33 kV transmission line connecting to Udipur substation. Middle Marshyangdi, 70 MW, Hydro power plant is also under construction and is going to generate power at the end of 2006. Besides these mentioned hydro power plants there are many other possibility of power generating sites available in this district. Lower Khudi, 2 MW, and Upper Nyadi 10 MW are already identified and are undergoing study.

10

Chapter 3. Methodology

CHAPTER 3

Methodology In Nepal, there are immense opportunities in the field of hydro power development. The record shows that Nepal has theoretical hydro power potential of 83,000 MW out of which 42,000 MW is technically and economically feasible. In Nepal many of I ndependent Power Producers (IPP) are showing strong interest in the development of small scale hydropower. Usually for small hydro Power, power evacuation is becoming great challenge because of difficult geographic structure and absence of electrical network/grid in the vicinity. Arrangement for accessing grid substation will make most of the small hydro power plant economically not feasible so for the small power plant which has enough possibility of local power consumption, it is required to develop a methodology that will make access to grid as well as satisfy local power demand. Keeping this in mind, this thesis tries to concentrate in identifying the evacuation system of Khudi Hydropower (KHP), Nyadi Hydro Power (NHP) and Lower Khudi Hydropower (LKHP) in western Nepal. Further, detail analysis of evacuation system of Khudi and Nyadi Hydro Power will be carried out using software developed in spread sheet, Carl 1.0-distribution load flow software and Netbas Simulation. The methodology adopted for identifying and designing evacuation system is mainly based on the availability of data for any selected small hydro power. The data collected in this regard should comprise of information on geography, demography, existing electrical network and future power expansion plans. After data collection comes analysis part, the analysis part is divided into two parts viz. technical and financial. Technical analysis results in feasibility of selected transmission line alternative regarding technical parameter like voltage, line length, power to be transmitted, power factor and efficiency. Financial analysis will decide in selection of one alternative among many technically feasible alternatives.

3.1

Data Collection

From data collection regarding existing electrical network of different district of western Nepal, help in locating the power house site of new coming small hydro power plants. Exact location of most of the new under study power plant is not known so knowledge of existing

11


electrical network including 11 kV distribution, 33 kV distribution or sub transmission line, 33/11 kV substation and 132/33/11 kV Grid substation is very essential because ultimately the power generated must be evacuated there. Difficulty in designing power evacuation system is quite similar for almost all identified new small hydro power plants. All hydro power station sites are far from major load centers and obviously far from grid access. So, in this thesis, for studying evacuation system of western Nepal, Lamjung district is selected because, in Lamjung district there are comparatively smaller hydropower plants identified by different IPPs and are under going different stages of study. The small hydropower plants identified in this district are 3.5 MW Khudi Hydro Power (KHP), 4.5 MW Lower Nyadi Hydro Power (LNHP), 2 MW Lower Khudi Hydro Power (LKHP) and 10 MW Upper Nyadi Hydro Power Plant (UNHP). Among these, Khudi Hydro Power Plant has started construction work, and detail study of Lower Nyadi Hydro Power is under progress. Now, for designing evacuation system for these two hydro power plants, data based on geography and demography is acquired from topographic map, data regarding all existing as well as proposed electrical network of whole Lamjung district is taken from 8th Power Report, NEA, and some of the data related to electrical infrastructure have been updated with the latest data acquired during field visit of Western Nepal. The existing electrical network of Lamjung district is presented in Appendix C.

3.2

Transmission line alternative

Topographic Map shows all required information regarding land, water, lakes, pond, rivers, stream, canals, dams, bridge, mountains, hills, valleys cliffs, towns, cities, roads, boundaries and other geographic and demographic features. Study of Topographic map gives the preliminary idea about the transmission line route. Selection of transmission line route is based on a procedure which should consider restricting factor like safety, engineering and technology, system planning, environmental, institutional and aesthetics. The transmission route selection is based on available right of way and results of system analysis. Usually the route is selected within the country on private right of way in order to obtain most possible direct route and to stay away from road, buildings, highway etc. After finalizing the transmission route/s technical and financial analysis is carried out for choosing best alternative

12


if there are many. Detail study for identifying the transmission line route is out of scope of this thesis. For carrying out technical and financial analysis of the selected transmission line, program developed on MS excel will be used, followed by Netbas simulation for studying system performance, finally using available data distribution system planning is carried out with Carl1.0 (program for load flow calculation of 11 kV radial distribution network).

3.3

Available Transmission Capacity

Transmission Capacity is the maximum power that can be delivered from power generating station to the distribution station. Transmission capacity depends on line length, size of conductors and voltage level. While determining transmission capacity of new transmission system, possibility of addition of new power plant is to be considered. Available Transmission Capacity (ATC) is difference between transmission margin and present line loading.

3.4

Transmission Margin

Transmission margin is the maximum allowable power that can be transmitted without violating the transmission line criteria which may be performance standard or control and protection settings used in primary and secondary distribution substations.

3.5

Performance of Transmission line

Efficiency and Voltage regulation are the key parameters that determine the performance of transmission line. For any type of transmission line, calculation based on ABCD constants for determining efficiency and regulation can be done using computer program. If the efficiency and regulation are not within prescribed value then it is necessary to revise the calculation using thick conductor cross-section and changing the conductor configuration. In some cases it may be necessary to use a higher transmission voltage in the revised design. Detail of transmission line design is presented in Appendix A.

3.6

Distribution system planning

The project will focus on the present distribution system and will work out for future distribution planning which is the most important parameter required for designing power evacuation system. Transmission and distribution planning is done so that present and future power required by local consumer is identified and help in designing required evacuation system. Distribution planning will be done using load forecasting of study area which includes

13


study of load growth pattern and load flow analysis. This thesis covers the load flow analysis part only.

3.7

Spread Sheet Calculation for Conductor selection and Voltage [2]

For the selection of optimum conductor size and transmission voltage a program is developed in spread sheet. The selection is based on capitalized cost per km of transmission line. This method is mainly applicable to transmission lines that are not subject to load growth. Such transmission line would be from new power plants to the nearest grid connection point in the existing system. Another important use of this spread sheet is to "screen" the number of alternatives down to a manageable level before full system studies are undertaken. Basic Formula

The selection of transmission lines for the planned power plants in Nepal are based on economic evaluation of different line/tower solutions over the lifetime of the project. The optimization takes into account the investment cost, cost of transmission losses and operation and maintenance costs. The calculation is performed on a km transmission line basis and is as such not dependent on the length of the transmission line. The following formulas apply to the calculation: K Total = K Invest ment + K Losses + K o& m

[NRs. / km]

Eq. 1

[kNRs. / Km]

Eq. 2

[NRs. / km]

Eq. 3

2

K Losses

 P  =  Peak   . R.T Loss .k E . D U  Rated 

K O& M = K Investment .

C O & M 100

D .

Where, P Peak =Maximum Transmitted Power [MW], U Rated = Rated AC line Voltage [kV], R = AC line resistance [? / km], T Loss = Loss Duration [hours], k E = Energy Cost [NRs/kWh], D = Discount Factor, C O& M = Annual Operation & Maintenance cost [% of initial investment].

14


Plant Loss Duration

The equivalent loss duration is calculated from the plant factors. The equivalent loss duration should be understood as the time the plant will have to operate on rated capacity in order to produce the annual losses, and is calculated from: T Loss

=

2 T Utilisatio n

8760

2 2  1  T Utilizatio   n   .1 + 1 −  2  8760 2     

[Hours]

Eq. 4

Energy Cost

The energy cost normally to be used for optimization of transmission line is the long run marginal cost of generation. In Nepal, it has been agreed that an average incremental cost of generation better reflects the real value and is therefore used. The average incremental cost of generation is 6.02 USC/kWh. Operation & Maintenance

The operation and maintenance cost of transmission line is set to 1.5% of initial investment by NEA. Typical figures range from 0.5% to 1.5%, and Nepal may be in the upper range of this due to the recurring monsoon and frequent landslides. An annual operation and maintenance cost of 1.5% has therefore been used in the optimization. Annual Outage

Outage means power transmission failure due to unavailability of transmission line during faulty condition. In Nepal, for 132 kV transmissions line the annual outage is taken as 0.28hrs/km. Discount Factor

The discount factor represents the discounted value of fixed annual payments of one unit each year of the lifetime. With 25 years technical lifetime and 10% discount rate, the discount factor is 9.08.

 (1 + i) N − 1 DF =  N   i (1 + i ) 

Eq. 5

Where, DF is discount factor, i is discount rate in percent, N is Number of compounding periods in years.

15


Spreadsheet Result:

Input to the spreadsheet program are line length, power factor, voltage level and power to be transmitted from generation source to distribut ion substation. The program will carry out transmission line design analysis using selected four different conductors from a given list. The result is the outcome of technical and financial analysis. For technical analysis the program will give, voltage regulation, efficiency of line and line loss. Changing either conductor size or voltage level, the result can be made within required voltage regulation and efficiency. Financial analysis is based on transmission line cost with selected conductor only. For more than one conductor satisfying both criteria i.e. voltage regulation and efficiency the best conductor is selected for minimum K Total in given in Equation 1. Input

Input parameters in spread sheet calculation for selecting conductor are power to be delivered in MW, line length (L) in km and power factor (Cosf ). Testing criteria

The selected conductor should meet both efficiency and voltage regulation criteria. If one of these criteria is violated, the conductor is not suitable for the transmission line. As per NEA Grid Code efficiency should be not less than 95.5% and voltage regulation should be ±10 %. Voltage Regulation

Voltage regulation of a line is the change in voltage at the receiving end when full load at a given power factor is removed keeping sending end voltage constant.

=

% Re gulation

V rnl − V rfl

Eq. 6

V rfl

Where, V rnl

=

magnitude of receiving-end voltage at no load.

V rfl

=

magnitude of receiving-end voltage at full load.

Transmission Efficiency η line

=

P R P s

* 100%

Eq. 7

Where, P R

=

Power to be delivered at receiving end

Ps

=

Power sent at the sending end

16


Conductor and Voltage Optimzation

4800

4300

3800

Weasel_33 Rabbit_33

] . s 3300 R N k [ t s o2800 C d e z i l 2300 a t i p a C

Beaver_33 Dog_33 Tiger_33 Wolf_33 Lynx_33 Panther_33 Dog_66 Wolf_66

1800

Panther_66 Lion_66

1300

800

300 1 Mw

2MW

3MW

4MW

5MW

6 MW

7MW

8 MW

Peak Load [MW]

Figure 3.1: Conductor

optimization sheet using spreadsheet

17


3.8

Carl 1.0

In order to evaluate the performance of a power distribution network and to examine the effectiveness of proposed alterations to a system in the planning stage, it is essential that a load flow analysis of the network is carried out. The load flow studies are normally carried out to determine: 1.

The flow of active and reactive power in network branches.

2.

Effect of additions or alterations on a system.

3.

Optimum system loading conditions.

4.

Optimum system losses.

Input

For this software-Carl1.0, the input parameters are related to the 11 kV radial distribution feeders only. Input data related to 11 kV feeder are; substation capacity (MVA), voltage level (kV), name of load centers, name of sending end node and receiving end node, distribution load (kVA of 11/0.4 kV distribution transformer), power factor, length of 11 kV line between sending end and receiving end of a branch and finally type conductor. This software allows only three conductor options viz. 'dog’, ‘rabbit’ and ‘weasel’ because in Nepal, only conductors ‘dog’, ‘rabbit’ and ‘weasel’ are used in the distribution level. Output

The output of the software is directly saved in the MS Excel sheet. The results of load flow are; total power loss in each branch feeders (sum of loss in all branches), total power flow in each branch, minimum voltage in percent; voltage drop in each branch, voltage at each receiving end, location of node with minimum voltage, length of different type of conductor used, total power loss of the feeder and total power flow in the feeder. Using this software conductor selection, feeder load management and voltage regulation can be done. This software is used just to study the status of local load centers.

3.9

Netbas Simulation

This software is developed by Powel Company, Norway. Netbas Simulation is very helpful in solving load flow ana lysis, short circuit analysis and other power system analysis. In this thesis, Netbas is used for determining the system performance after connecting a small power plant in

18


the existing electrical network. The comparison between status of existing electrical network before and after connecting new power plant will definitely help in selecting best evacuation option for upcoming hydropower plant. As per grid code, NEA, in Nepal study of system performance is necessary for any new hydro power plant more than 1 MW, willing to connect to the grid. System performance shall include the following information: 1.

Power flow direction during different time frame, loading conditions.

2.

Change in voltage regulation in existing electrical network

3.

Change in transmission line loss in existing electrical network.

These required data can be easily determined using Netbas Simulation

3.10 Evacuation System for KHP, LNHP and LKHP. The methodology described above is used to study evacuation system of KHP, LNHP and LKHP in Lamjung district. These power plants are under different stages of development. The present status shows that KHP will come first then LNHP and at last LKHP. For all these power plants the nearest available existing grid is 33/11 kV, 5 MVA, Udipur substation which is fed by 132/33 kV grid substation at Damauli, 34.5 km away at Tanahu district. There are no other options available for power evacuation from these power plants. Therefore, this thesis concentrates on detail study for evacuating power using existing transmission system for different loading conditions.

19

Chapter 4. Results and Discussion

CHAPTER 4

Results And Discussions Existing system in Lamjung district is shown below. Udipur substation is 14 km away from Dumre substation and connected with 33 kV transmission line with conductor 'dog'. Dumre, Udipur and Anbu Khaireni substations are fed by Damauli 132/33 substation through 14.5 km long 33 kV transmission line from Damauli S/S to Dumre S/S. Single line diagram of existing 33 kV sub transmission network is shown in figure below.

Figure 4.1: Existing Electrical System of Lamjung District

4.1

Existing System Result

Existing system analysis will help in finding out the present performance and make us able to compare with different options of addition of hydro power plant or addition of bulk load. Three area substations Dumre S/S, Udipur S/S and Anbu S/S and one grid substation, Damauli S/S will be affected by addition of upcoming SHP. Load flow is carried out for different loading condition.

20


Case I : Full Load

In 100% load, i.e. 15 MVA (sum of full load of three substation, 13.5 MW at 0.9 pf), swing bus- Damauli substation will generate 14.83 MW including line losses. Maximum voltage drop is at Udipur which is 13.68 % i.e. voltage at Udipur is only 28.486 kV. In this case DamauliDumre line section is over loaded, 106.23%. The result of Netbas Simulation for full load case is tabulated below. Table.4.1: Full Sub Stations Load, Existing System

Conductor

Dog

Generation at Damauli (slack bus)

14.83 MW, 8.32 Mvar

Total voltage independent load

13.5 MW, 6.58 Mvar

Total Loss in line sections

1.33 MW, 1.74 Mvar

Total % of transmission Loss

8.97 %

Max. Voltage Drop and location

13.68 %, Udipur

Heaviest loaded line

Damauli-Dumre, 106.23%

Case II: 70 % Load

In 70% load, i.e. 10.5 MVA (9.45 MW at 0.9 pf), the swing bus, Damauli substation will generate 10.045 MW including line losses. Maximum voltage drop is at Udipur which is 9.11% i.e. voltage at Udipur is only 29.995 kV. In this case Damauli- Dumre section is heaviest loaded line, 71.22 %. The result of Netbas Simulation for this case is tabulated below. Table.4.2: 70 % Substations Load, Existing System

Conductor

Dog


10.045 MW, 5.39 Mvar


9.45 MW, 4.61 Mvar


0.6 MW, 0.78 Mvar

Total % of transmission Loss

6.35 %


9.11 %, Udipur



21


Case III: 50 % Load

In this case all three area substations are considered to be operated in half load only. Total generation in Damauli S/S is 7.04 MW including losses 0.29 MW in all line sections and the total load of all substations is 6.75 MW. The maximum voltage drop is 6.71 % at Udipur S/S, which is 30.92 kV. The heaviest loaded line is Damauli-Dumre, 49.6%. Table 4.3: 50% Substations L oad, Existing System

Conductor

Dog


7.04 MW, 3.67 Mvar


6.75 MW, 3.29 Mvar


0.29 MW, 0.38 Mvar

Total % of Transmission Loss

4.12 %


6.31 %, Udipur


Damauli-Dumre,49.6%

Case IV: 30 % Load

In this test case all substations are considered to b e running in 30% loading. Total power drawn from Damauli S/S is 4.15 MW including 0.099 MW losses in all line sections. The maximum voltage drop is 3.69 % at Udipur which is 31.78 kV. In this case also the heaviest loaded line is Damauli-Dumre, 29.06%. Table.4.4: 30 % Substations Load, Existing System

Conductor

Dog


4.15 MW, 2.01 Mvar


4.05 MW, 1.97 Mvar


0.099 MW, 0.13 Mvar


2.38 %


3.69%, Udipur



22


Case V: 10 % Load

In this test case all substations are considered to be running in 10 % loading. Total power drawn from Damauli S/S is 1.36 MW including 0.01 MW losses in all line sections. The maximum voltage drop is 1.2 % at Udipur which is 32.605 kV. Table4.5: 10 % Substations Load, Existing System

Conductor

Dog


1.36 MW, 0.67 Mvar


1.35 MW, 0.66 Mvar


0.01 MW, 0.14 Mvar


0.74 %


1.2%, Udipur


Damauli-Dumre,

Case VI: 100% load with “Wolf”

In full load capacity, with conductor ‘wolf’ the total system loss is 6.05% which is unacceptable and the voltage drop is 10.41%, so the existing system will be inefficient even if conductor wolf is used. Table 4.6: 100% Substations load with 'wolf', Existing system

Conductor

Wolf


14.37 MW, 8.15 Mvar


13.5 MW, 6.58 Mvar


0.87 MW, 1.57 Mvar


6.05 %


10.41 %, Udipur


Damauli-Dumre

Case VII: 80% load with “Wolf”

In 80% load capacity the total line loss is 4.5% and maximum voltage drop is 8.1%. Generation at Damauli S/S is 11.31 MW and total substation load is 10.8 MW.

23


Table 4.7: 80 % Substations load with 'wolf', Existing system

Conductor

Wolf


11.31 MW, 6.215 Mvar


10.8 MW, 5.26 Mvar


0.511 MW, 0.952 Mvar


4.5%


8.1 %, Udipur



Case VIII: 50% load with “Wolf”, Existing System

In this case the system performance is within acceptable limits. The voltage regulation of 4.88% and total transmission loss of 2.8% with total gene ration of 6.95 MW at slack bus makes the system quite normal. Table 4.8: 50% Substat ions load with 'Wolf', Existing system

Conductor

Wolf


6.95 MW, 3.64 Mvar


6.75 MW, 3.3 Mvar


0.195 MW, 0.35 Mvar


2.8 %


4.88 %, Udipur


Damauli-Dumre,49.0%

Discussion: Existing Electrical Network

Usually the substation capacity is determined from the peak load forecast of 15th year from the date of its construction. The analysis of system is carried out for different loading condition in the substations. From load flow analysis using Netbas simulation it is found that transmission capacity of Damauli-Dumre 33 kV transmission line is 13.5 MW without over loading. Full capacity of this line cannot be used because of poor voltage regulation (13.68 %) and transmission loss (8.97 %). From Case III Transmission Margin is 7 MW. If the total load demand exceeds 50%- case III, then the total transmission loss exceeds 4% and in this case the total power drawn from Damauli S/S (swing bus) is 7 MW. For Case I, II and III, there is no 24


Available Transmission Capacity in existing system because total line loss is more than 4%. In case IV the total line loss is only 2.38% so more power can be drawn from Damauli S/S therefore ATC is 2.54 MW and in case V ATC is 5.68 MW. As the existing system performance using conductor ‘dog’ is very inefficient when the load demand exceeds 50% of total substation capacity. Therefore for better performance conductor with higher cross section shall be used. Analysis of system performance using conductor ‘wolf ‘ shows that the existing system will be acceptable up to load demand of 80% of total substation capacity. By changing the existing conductor "Dog" with conductor "Wolf" the transmission margin can be increased to 11 MW.

4.2

KHP Evacuation System

This section shows the analysis for Khudi Hydro Plant (KHP) power evacuation. As Lower Nyadi Hydro Project (LNHP) is also coming in near future so the Khudi Switching Station will connect both power sources and feed down to Damauli S/S through Udipur S/S and Dumre S/S. First step is to analyze transmission system of KHP up to Khudi Switching station (KSw/S) and then Udipur S/S using spreadsheet calculation. Transmission line from KHP to Khudi switching station is only 0.9 km and this line will be used only for transferring power from KHP to Khudi switching station. From spread sheet calculation in 33 kV voltage level conductor ‘Beaver’, ‘Dog’, ’Wolf’ and ‘Panther’ is found to be technically feasible but financial analysis shows that conductor ‘Wolf’ is the best having lowest NPV of Investment (inclusive of losses, O&M and outages over the period of 25 years). The spread sheet result is tabulated below: Table 4.9: Spread Sheet Calculation for KHP Evacuation System

Conductor Line Length (km) Receiving End Voltage (kV) Voltage Regulation (%) Line Losses (kW) % transmission loss Line Efficiency (%): Power Delivered (MW)

Technical Part Beaver 0.9 32.95 0.23 4.80 0.2 99.86 3.49

Economical Part NPV of Investment inclusive of losses, 1556 O&M and outages (NRs.'000)

Dog

Wolf

Panther

0.9 32.96 0.13 3.44 0.1 99.9 3.49

0.9 32.97 0.1 2.3 0.07 99.93

0.9 32.97 0.09 1.72 0.05 99.95

1375

1335

1378

25



4800

4300

3800 ] . s 3300 R N k [ t s o 2800 C d e z i l 2300 a t i p a C

Weasel_33 Rabbit_33 Beaver_33 Dog_33 Tiger_33 Wolf_33 Lynx_33 Panther_33

1800

1300

800

Wolf 33

300 1 Mw

2MW

3MW

4MW

5MW

Peak Load [MW]

Figure 4.2: Conductor Selection for KHP evacuation

Before LNHP connected to the Khudi Switching Station KHP will get connected in Udipur Substation through 14km long 33 kV transmission line from Khudi Switching Station to Udipur S/S. Now in this case the total transmission length is 14.9 km and spread sheet calculation shows that conductor "Wolf" is best and have lowest NVP of Investment. The details of spread sheet result are tabulated below. Table.4.10: Spread Sheet calculation for KHP Evacuation System

Conductor Line Length (km) Power to be Transmitted (MW) Receiving End Voltage (kV) Voltage Regulation (%) Line Losses (kW) % transmission loss Line Eficiency (%): Power Delivered at the load end (MW) NPV of Investment inclusive of Losses, O&M and Outages (NRs.’000)

Technical Part Beaver 14.9 3.50 32.11 2.71 79.48 2.21 97.79 3.41 Economical Part 25696

Dog 14.9 3.50 32.29 2.16 56.90 1.59 98.41 3.43

Wolf 14.9 3.5 32.44 1.69 38.16 1.07 98.93 3.45

Panther 14.9 3.5 32.52 1.44 28.45 0.8 99.2 3.46

22717

22083

22803

For studying the affect of connecting KHP to Udipur S/S Netbas Simulation is used. Power from KHP will get grid access at Udipur S/S and will feed power to local area through 33/11

26


kV Udipur S/S. The excess power is transmitted to Dumre S/S and feed power there also and finally excess power will be transmitted to Grid. Netbas Simulation is carried out for studying the following system performance under different loading condition of Substations.

Figure 4.3: KHP Evacuation System

Case I: Full load

In full load, i.e. 15 MVA (13.5 MW at 0.9 pf), swing bus i.e. Damauli substation will generate 10.73 MW including line losses. Power generation from Khudi Power plant is 3.5 MW. Maximum voltage drop is at Anbu Khaireni which is 8.66 % i.e. voltage at Anb u Khaireni is only 30.14 kV. In this case Damauli- Dumre line section is heaviest loaded with 73.58%. The result of Netbas Simulation for full load case is tabulated below. Table.4.11: Full Load, KHP Power Evacuation

Conductor Generation at Damauli (slack bus) Total Generation Total voltage independent load Total Loss in line sections % of total transmission line loss Max. Voltage Drop and location Heaviest loaded line

Dog 10.73MW, 4.85 Mvar 14.23 MW, 7.7 Mvar 13.5 MW, 6.58 Mvar 0.68 MW, 0.9 Mvar 4.77 % 8.66%, AnbuKhareni Damauli-Dumre, 73.58%

27


Case II: 70% load In 70% load, i.e. 10.5 MVA (9.45 MW at 0.9 pf), the swing bus, Damauli substation will

generate 6.27 MW including line losses. Power generation from KHP is 3.5 MW. Maximum voltage drop is at AnbuKhaireni which is 5.75 % i.e. voltage at AnbuKhaireni is only 31.1 kV. In this case Damauli- Dumre section is heaviest loaded line, 45.7 %. The result of Netbas Simulation for this case is tabulated below. Table.4.12: 70 % Substation Load, KHP Powe r Evacuation


Dog 6.27 MW, 3.76 Mvar 9.77 MW, 5.15 Mvar 9.45 MW, 4.61 Mvar 0.29 MW, 0.38 Mvar 2.97 % 5.75%, AnbuKhareni Damauli-Dumre, 45.7%

Case III: 50% load In this case all three area substations are considered to be operated in half load only. Total

power drawn from Damauli S/S is 3.44 MW including losses 0.16 MW in all line sections and the total load of all substations is 6.75 MW (at 0.9 pf). Power gene ration from KHP is 3.5 MW. The maximum voltage drop is 3.94% at AnbuKhaireni S/S, which is 31.70 kV. The heaviest loaded line is KHP-Khudi Sw/S, 30.91%. Table.4.13: 50 % Substatio n Load, KHP Power Evacuation


Dog 3.44 MW, 3.15 Mvar 6.94 MW, 3.64 Mvar 6.75 MW, 3.3 Mvar 0.16 MW, 0.21 Mvar 2.3 % 3.94 %, AnbuKhaireni KHP-Khudi Sw/S,30.91 %

Case IV: 30% load In this case all substations are considered to be running in 30% loading. Total power drawn

from Damauli S/S is 0.69 MW including 0.11 MW losses in all line sections. Power generation from KHP is 3.5 MW. Power generation from KHP is 3.5 MW. The maximum voltage drop is 2.21 % at AnbuKhaireni which is 32.27 kV. In this case also the heaviest loaded line is KHP-Khudi Sw/S, 30.8 %.

28


Table.4.14: 30 % Substatio n Load, KHP Power Evacuation

Conductor Generation at Damauli (slack bus) Total Generation (MW) Total voltage independent load Total Loss in line sections % of total transmission loss Max. Voltage Drop and location Heaviest loaded line

Dog 0.69 MW, 2.64 Mvar 4.19 MW, 2.26 Mvar 4.05 MW, 1.97 Mvar 0.11 MW, 0.15 Mvar 2.62 % 2.21%, AnbuKhaireni KHP-Khudi Sw/S, 30.8%

Case V: 10% load In this case all substations are considered to be running in 10 % loading. Total power fed to

Damauli S/S is 1.98 MW including 1.43 MW losses in all line sections. Power generation from KHP is 3.5 MW. The maximum voltage drop is 0.55 % at AnbuKhaireni which is 32.82 kV. In this case also the heaviest loaded line is KHP-Khudi Sw/S, 32.39%. Table.4.15: 10 % Substation Load KHP Power Evacuation


Dog -1.98 MW, 2.21 Mvar 1.53 MW, 1.0 Mvar 1.35 MW, 0.66 Mvar 0.143 MW, 0.19 Mvar 9.34 % 0.55%, AnbuKhaireni KHP-Khudi Sw/s, 32.39%

Case VI: 100% load with conductor ‘wolf’

As from economical analysis conductor ‘wolf’ is the best one. Using this conductor the total transmission loss is 3.42%. Maximum voltage drop is 7.33% only. The power drawn from Damauli S/S is 10.52 MW and power generation from KHP is 3.5 MW. Table.4.16: 100% Load with 'Wolf', KHP power evacuation


Wolf 10.52MW, 5.23 Mvar 14.02 MW, 7.62 Mvar 13.5 MW, 6.58 Mvar 0.48 MW, 0.84 Mvar 3.42 % 7.33%, AnbuKharireni Damauli-Dumre, 73.4%

29


Case VII: 50% load with conductor ‘wolf’

In this case using wolf conductor the system performance is very much improved. The total line loss is only 1.62% and maximum voltage drop is 3.41% at AnbuKhaireni. Table.4.17: 50% Substation Load with 'Wolf', KHP power evacuation


Wolf 3.39 MW, 3.11 Mvar 6.89 MW, 3.62 Mvar 6.75 MW, 3.29 Mvar 0.112 MW, 0.196 Mvar 1.62 % 3.41%, AnbuKhaireni KHP-Khudi Sw/S, 30.94%

Effect in NEA line:

Udipur S/S is feeding in Lamjung district through outgoing four feeders. Power source for this S/S is Damauli grid S/S 34.4 km away. KHP, on the other hand is only 14 .9 km away from Udipur S/S and connecting 33 kV transmission line from KHP to Udipur will change the existing electrical system. Existing transmission line sections are Udipur S/S to Dumre S/S (USS to DuSS), Dumre SS to Damauli SS (DuSS to DaSS) and Dumre SS to AkSS (Dumre SS to Anbu Khaireni SS).

Case I: 100 % loading

With addition of KHP in Udipur S/S line losses in three existing section of NEA has improved also voltage drop in these sections has greatly reduced. The total losses in these line sections reduce from 1.326 MW to 0.606 MW. The maximum voltage drop in Dumre – Damauli section has also improved from 10.29 % to 6.61 %. The result shows that if KHP is connected then Udipur, Anbu Khaireni and Damauli S/Ss can be run in full load without violating the voltage regulation and efficiency limits. The result from Netbas Simulation is tabulated below.

30


Table.4.18: 100% Substation Load, effect in existing system with KHP.

SNo

Section

Length, km

1

USS to DuSS

2

DuSS to DaSS DuSS to AkSS

3

New Line Loss (kW) 7.88

Previous V New Drop % V Drop %

20

Previous Line Loss (kW) 170.06

5.03

0.408

14.5

1058.17

507.74

10.29

6.61

12

97.92

91.13

2.92

2.69

Total 1326.15

606.75

Case II: 70% loading

After addition of power from KHP in Udipur S/S line losses in three existing section of NEA has improved. Voltage drop in these sections has greatly reduced. The total losses in these lines sections reduce from 0.594 MW to 0.238 MW. The maximum voltage drop in Dumre – Damauli section has also improved from 6.63 % to 4.26 %. The result shows that if KHP is connected then Udipur S/S, Anbu Khaireni S/Ss and Damauli S/S can be run without violating the voltage regulation and efficiency limits. The result from Netbas Simulation is tabulated below. Table.4.19: 70% Substation Load, effect in existing system with KHP.

SNo

Section

1

USS to DuSS

2


3

Length, km 20

Previous Line Loss 75.15

New Line Loss 1.17

Previous V New Drop V Drop 3.17 1.91

14.5

475.6

195.75

6.63

4.26

12

43.95

41.94

1.85

1.76

Total 594.7

238.86

Case III: 50 % loading

After addition of power from KHP in Udipur S/S line losses in three existing section of NEA has improved. Voltage drop in these sections has greatly reduced. The total losses in these lines sections reduce from 0.288 MW to 0.111 MW. The maximum voltage drop in Dumre – Damauli section has also improved from 4.51% to 2.84 %. The result shows that if KHP is connected then Udipur S/S, Anbu Khaireni S/Ss and Damauli S/S can be run in without

31


violating the voltage regulation and efficiency limits. The result from Netbas Simulation is tabulated below. Table.4.20: 50% Substation Load, effect in existing system with KHP.

SNo

Section

1

USS to DuSS

2


3

Length, km 20


New Line Loss 10.93


14.5

230.59

79.61

4.51

2.84

12

21.29

20.6

1.25

1.21

Total 287.97

111.14

Case IV: 30 % Loading

After addition of power from KHP in Udipur S/S line losses in three existing section of NEA has improved. Voltage drop in these sections has greatly reduced. The total losses in these lines sections reduce from 0.098 MW to 0.064 MW. The maximum voltage drop in Dumre – Damauli section has also improved from 2.58 % to 1.53 %. The result shows that if KHP is connected then Udipur S/S, Anbu Khaireni S/Ss and Damauli S/S can be run in without violating the voltage regulation and efficiency limits. The result from Netbas Simulation is tabulated below. Table.4.21: 30% Substation Load, effect in existing system with KHP

SNo

Section

1

USS to DuSS

2


3

Length, km 20


New Line Loss 30.32


14.5

79.22

27.24

2.58

1.53

12

7.31

7.15

0.71

0.71

Total 98.82

64.71

Case V: 10 % Loading

After addition of power from KHP in Udipur S/S line losses in three existing section of NEA has improved. Voltage drop in these sections has greatly reduced. The total losses in these lines sections increase from 0.01 MW to 0.091 MW. The maximum voltage drop in Dumre–Damauli section has also improved from 0.82 % to 0.33 %. Unlike other cases the

32


result shows that in lightly loaded condition system performance is better with out KHP. The result from Netbas Simulation is tabulated below. Table 4.22: 10% Substation Load, effect in existing system with KHP.

S.No

Section

1

USS to DuSS

2


3

Length, km 20


New Line Loss 58.17


14.5

8.43

32.14

0.82

0.33

12

0.78

0.77

0.23

0.29

Total 10.31

4.3

91.48

Results of LNHP Evacuation System

LNHP to Khudi switching station is about 7 km and this is the only alternative to evacuate power to grid. Power generation from LNHP is 4.5 MW. This power has to be evacuated to nearest available grid and that would be Udipur S/S which is 14 km away from Khudi switching station. New 33 kV, 7 km long transmission line is needed for power evacuation. From spreadsheet calculation station following results is obtained. Table 4.23: LNHP evacuation system

Conductor Efficiency Voltage Regulation % of transmission loss NPV of Investment

Beaver 98.65 1.63 1.35 16,780

Dog 99.03 1.3 0.97 14,163

Wolf 99.35 1.02 0.65 12,854

Panther 99.51 0.87 0.49 12,664

Details of spread sheet calculation are presented in Appendix D. Conductors "Panther" is recommended because of lowest investment.

33



4800

4300

3800 ] . s 3300 R N k [ t s 2800 o C d e z i l 2300 a t i p a C

Weasel_33 Rabbit_33 Beaver_33 Dog_33 Tiger_33 Wolf_33 Lynx_33 Panther_33

1800

Panther_33 Panther_33

1300

Panther_33 Panther_33

Panther_33

800

300 1 Mw

2MW

3MW

4MW

5MW

Peak Load [MW]

Figure 4.4: Conductor Optimization chart for LNHP only

Discussion:

From technical analysis conductors ‘beaver’, ‘dog’, ‘wolf’ and ‘Panther’ all are acceptable but from conductor optimization chart in Figure 6: for evacuating power of 4.5 MW conductor ‘Panther’ will be economical.

4.4

KHP and LNHP Evacuation system

Power Evacuation from Khudi Hydro Power and Nyadi Hydro Power will be more fruitful if certain portion of power can be consumed locally. The priority is given for local consumption because such small hydro power plant located very far from grid access. After connecting NHP and KHP at Khudi switching station the total power will be directly fed to 5 MVA, 33/11 Udipur substation through 14 km long 33 kV new transmission line and excess power after satisfying local demand in Udipur substation will be fed to Dumre Substation through 20 km long existing 33 kV transmission line and the rest at 132/33/11 kV, Damauli Grid Substation through 14.5 km long 33 kV existing transmission line. From spread sheet calculation for power transmission in 33 kV level and 66 kV level from Khudi Switching station to Udipur Substation following results are obtained.

34


Table 4.24: LNHP and KHP 14 km long 33 kV transmission line

Conductor Employed

Dog

Line Length (km)

Wolf 14

Voltage Regulation (%) Line Losses (kW) % transmission loss Line Eficiency (%): Power Delivered at the load end (MW) NPV of Investment inclusive of Losses, O&M and Outages. (NRs.’000)

Lion

8

14 8

14 8

14 8

31.27

31.65

31.84

31.91

5.24

4.10

3.51

3.31

353.54

237.06

176.77

157.23

3.77

2.56

1.92

1.71

96.23

97.44

98.08

98.29

8.62

8.74

8.80

8.82

78,395

60,528

52,264

50,009

Power to be Transmitted (MW) Receiving End Voltage (kV)

Panther

Table 4.25: LNHP and KHP 14 km long 66 kV transmission line

Conductor Employed

Dog 14

Lion

8

14 8

14 8

65.10 1.37 88.38 0.97 99.03 8.89

65.29 1.08 59.27 0.65 99.35 8.92

65.39 0.93 44.19 0.48 99.52 8.93

65.42 0.88 39.31 0.43 99.57 8.94

44,876

42,255

41,883

42,185

Power to be Transmitted ( MW)

NPV of Investment inclusive of Losses, O&M and Outages. (N Rs.’000)

Panther 14 8

Line Length (km)

Receiving End Voltage (kV) Voltage Regulation (%) Line Losses (kW) % transmission loss Line Eficiency (%): Power Delivered at the load end (MW)

Wolf

In this case conductor dog, wolf , panther and lion all can be used because all satisfy the prescribed technical criteria but if better efficiency and voltage regulation is to be considered then higher conductor is to be chosen. From conductor optimization chart 66kV conductor 'Panther' is the best option for power evacuation.

35



4800

4300

3800

Weasel_33 Rabbit_33

] . s 3300 R N k [ t s o2800 C d e z i l 2300 a t i p a C

Beaver_33 Dog_33 Tiger_33 Wolf_33 Lynx_33

Panther_66

Panther_33 Dog_66 Wolf_66

1800

Panther_66 Lion_66

1300

800

300 1 Mw

2MW

3MW

4MW

5MW

6 MW

7MW

8 MW

9 MW

Peak Load [MW]

Figure 4.5: Conductor and Voltage selection for KHP and LNHP

36


Discussion:

Although for transmitting 15 MW power from KSw/S to Udipur S/S 66 kV, conductor 'Panther' is most economical, it is only for transmission line. If 66 kV is chosen the substation cost will make the NPV of Investment greater than transmission system with conductor 'Dog'. Netbas Result:

Netbas Simulation gives us the clear picture of system performance during full load, normal load and off load. For analyzing existing system performance load flow is carried out for 100% load, 50% load and 10% load of substation capacity. The result is presented below

Figure 4.6: KHP and LNHP evacuation system

Case I: Full Load In full load, i.e. 15 MVA (13.5 MW at 0.9 pf), swing bus i.e. Damauli substation will

generate 6.33 MW including line losses. Power generation from KHP and LNHP are 3.5 MW, 4.5 MW respectively. Maximum voltage drop is at Anbu Khaireni which is 7.95 % i.e . voltage at Anbu Khaireni is only 30.37 kV. In this case Damauli- Dumre section is heaviest

37


loaded line with 57.35 %. The result of Netbas Simulation for full load case is tabulated below. Table.4.26: 100% substation load, KHP and LNHP power evacuation

Conductor Generation at Damauli (slack bus) Total Generation Total voltage independent load Total Loss in line sections % of Total Transmission Loss Max. Voltage Drop and location Heaviest loaded line

Dog 6.33 MW, 6.68 MVAR 14.33 MW, 7.33 MVAR 13.5 MW, 6.53 MVAR 0.739 MW, 0.971 MVAR 5.15% 7.95%, AnbuKhaireni Damauli-Dumre, 57.53%

Case II: 70% load

In 70% load, i.e. 10.5 MVA (9.45 MW at 0.9 pf), the swing bus, Damauli substation will generate 2.15 MW including line losses. Power generation from KHP and LNHP are 3.5 MW and 4.5 MW respectively. Maximum voltage drop is at AnbuKhaireni which is 5.38% i.e. voltage at AnbuKhaireni is only 31.22 kV. In this case Khudi Sw/S-Udipur S/S section is heaviest loaded line, 49.91%. The result of Netbas Simulation for this case is tabulated below. Table 4.27: 70% substation load, KHP and LNHP power evacuation

Conductor Generation at Damauli (slack bus) Total Generation Total voltage independent load Total Loss in line sections % of Total Transmission Loss Max. Voltage Drop and location Heaviest loaded line

Dog 2.15 MW, 6.14 MVAR 10.15 MW, 5.73 MVAR 9.45 MW, 4.58 MVAR 0.607 MW, 0.796 MVAR 5.98% 5.38%, AnbuKhaireni Khudi Sw/S-Udipur SS, 49.91%

Case III: 50% load

In this case all three area substations are considered to be operated in half load only. Total power fed to Damauli S/S is 0.53 MW including losses 0.63 MW in all line sections and the total load of all substations is 6.75 MW (at 0.9 pf). Power generation from KHP and LNHP are 8 MW. The maximum voltage drop is 3.76% at AnbuKhaireni, which is 31.76 kV. The heaviest loaded line is Khudi Sw/S-Udipur S/S, 50.62%.

38


Table 4.28: 50% substation load, KHP and LNHP power evacuation

Conductor Generation at Damauli (slack bus) Total Generation Total voltage independent load

Dog -0.53 MW, 5.87 MVAR 7.47 MW, 4.45 MVAR 6.75 MW, 3.27 MVAR

Total Loss in line sections % of Total Transmission Loss Max. Voltage Drop and location Heaviest loaded line

0.63 MW, 0.823 MVAR 7.8% 3.76%, Anbu Khudi Sw/s–USS, 50.62 %

Case IV: 30% load In this case all substations are considered to be running in 30% loading. Total power fed to

Damauli S/S is 3.13 MW including 0.0.724 MW losses in all line sections. Power generation from KHP and LNHP are 3.5 MW and 4.5 MW respectively. The maximum voltage drop is 2.2 % at AnbuKhaireni which is 32.27 kV. In this case also the heaviest loaded line is Khudi Sw/S-Udipur S/S, 52 %. Table 4.29: 30% substation load, KHP and LNHP power evacuation

Conductor

Dog

Generation at Damauli (slack bus) Total Generation Total voltage independent load

-3.13 MW, 5.67 MVAR 4.87 MW, 3.3 MVAR 4.05 MW, 1.96 MVAR

Total Loss in line sections % of Total Transmission Loss Max. Voltage Drop and location Heaviest loaded line

0.724 MW, 0.95 MVAR 9.05% 2.2%, AnbuKhaireni Khudi Sw/S-Udipur S/S, 52.01%

Case V: 10% load

In this case all substations are considered to be running in 10 % loading. Total power fed to Damauli S/S is 5.66 MW including 0.89 MW losses in all line sections. Power generation from KHP and LNHP are 3.5 and 4.5 MW respectively. The maximum voltage drop is 0.71 % at AnbuKhaireni which is 32.76 kV. In this case also the heaviest loaded line is Khudi Sw/S-Udipur S/S, 53.96%. Table 4.30: 10% substation load, KHP and LNHP, power evacuation

Conductor Generation at Damauli (slack bus)

Dog -5.66 MW, 5.54 MVAR

Total Generation Total voltage independent load

2.34 MW, 2.24 MVAR 1.35 MW, 0.65 MVAR

Total Loss in line sections % of total Transmission Loss Max. Voltage Drop and location Heaviest loaded line

0.89 MW, 1.17 MVAR 11.125%** 0.71 %, AnbuKhaireni KH-1 – KH-3, 53.96 %

39


Discussion

Using spreadsheet calculation it is found that, to transmit 6.65 MW from Khudi Sw/S to Damauli S/S, conductor 'Bear' will make total transmission loss reduced to 4.0 %, if it is used to transmit power from Khudi Sw/S to Damauli S/S. Loss in 14 km line section to transmit 8 MW from Khudi Sw/s to Udipur S/S is 44.19 kW, loss in 20 km line section to transmit 7.55 MW from Udipur S/S to Dumre S/S is 142.43 kW and loss in 14.5 km lo ng transmission from Dumre S/S to Damauli S/S is 80.11 kW resulting total transmission loss of 266.13 kW. Effect in NEA line Case I: 100 % loading

With addition of KHP and LNHP in Udipur S/S, line losses in three existing section of NEA has improved; also voltage drop in these sections has greatly reduced. The total losses in these line sections reduce from 1.32 MW to 0.63 MW. The maximum voltage drop in Dumre – Damauli section has also improved from 10.29 % to 2.6 %. The result shows that if KHP and LNHP are connected then Udipur, Anbu Khaireni and Damauli S/Ss can be run in full load without violating the voltage regulation and efficiency limits. The result from Netbas Simulation is tabulated below. Table 4.31: 100% load, effect in existing system, KHP &LNHP evacuation

SNo

Section

Length, km

1

USS to DuSS

2


3

20

Previous Line Loss (kW) 170.06

New Line Previous V New Loss Drop % V Drop (kW) % 229.9 5.03 0.45%

14.5

1058.17

309.8

10.29

2.6%

12

97.92

89.41

2.92

2.64%

Total 1326.15

629.11

Case II: 70% loading

After addition of power generated from KHP and LNHP in Udipur S/S line losses in three existing section of NEA has improved. Voltage drop in these sections has greatly reduced. The total % of transmission losses in these lines sections reduce from 6.3% to 3.6 %. The result from Netbas Simulation is tabulated below.

40


Table 4.32: 70% load, effec t in existing system, KHP &LNHP evac uation

SNo

Section

1

USS to DuSS

2 3


Length, km 20

Previous Line Loss kw 75.15

14.5 475.6 12 43.95 Total 594.7

New Line Loss, kw

146.57 154.47 41.46 342.5

Case III: 50 % loading

After addition of power from KHP and LNHP in Udipur S/S line losses in three existing section of NEA has improved. Voltage drop in these sections has greatly reduced and with acceptable limit. The total losses in these lines sections increases from 0.288 MW to 0.63 MW. The result from Netbas Simulation is tabulated below. Table.4.33: 50% load, effec t in existing system, KHP &LNHP eva cuation

SNo

Section

Length, km

1

USS to DuSS

20

2 3


14.5 12

Previous Line Loss, kw 36.09

230.59 21.29 Total 287.97

New Line Loss, kw 207.77

126.95 20.45 355.17

Discussion

After addition of power generated from KHP and LNHP the performance of existing line of NEA (from Damauli S/S to Udipur S/S) has improved for 70% and 100% loading case but for load 50% and less performance is worse because all the excess power has to be fed to Damauli S/S which 34.5 km away from Udipur S/S.

4.5

System with KHP, LNHP and LKHP

There is possibility of coming another Hydro Power 500 m away from KSw/S (Khudi switching station). This new power plant is Lower Khudi Hydro Plant with capacity of 2 MW. There is only one option for evacuating power from LKHP at KSw/S. The system performance using Netbas Simulation shows that addition of this power plant will make existing system inefficient. In full load case total transmission loss is 5.33% and maximum voltage drop is 7.37% at Anbu Khaireni.

41


Figure 4.7: KHP, LNHP and LKHP e vacuation system Table.4.34: System Performance with KHP, LNHP and LKHP

Substation Loading (%) 100 70 50 30

Total Generation, MW 15 10.5 10 10

Total loss in line sections MW MVar 0.8 1.048 0.901 1.182 1.022 1.223

% of total transmission loss 5.33% 8.64% 8.64 % 12.23 %

Max. Voltage drop, location 7.37%, AnbuKhaireni 5.2%, AnbuKhaireni 3.81 % 2.48 %

Discussion

From above table, only in full load case existing system looks fine but in lightly loaded condition the system will be worse. Using conductor 'Lion' in new section KSw/S-USS the total transmission loss can be reduced to 4.68%.

4.6

KHP, LNHP, LKHP and Chame substation

Chame substation is located in Manang district. In Chame the proposed substation size is 1.5 MVA. This S/S is 50 km away from Khudi switching station. Using transmission voltage 33 kV with conductor 'dog' the system performance is checked in NETBAS simulation and is tabulated below.

42


Figure 4.8: Evacuation system with Chame load Table 4.35 System performances with KHP, LNHP, LKHP and Chame substation

Substations Total loading (%) 100 70 50 30

Total Generation, MW 15.67 10 10 10

Total loss in line % of total sections MW transmission loss 0.75 0.88 0.994 1.22

4.7% 8.77% 9.94 12.22%

Max. Voltage drop, location (%) 7.34%, Anbu 3.76%, Anbu 2.39% 2.48%

Discussion:

In full load, only 5.67 MW power is drawn from Damauli S/S and total generation from three power plants is 10 MW. From NETBAS calculation the highest loss of 1.22 MW will occur during 30% of total substation loading i.e. 4.05 kW and the transmission loss in percentage is 12.22 %. Maximum voltage drop of 7.34 % is at AnbuKaireni.

4.7

Load flow analysis of four feeders of Udipur S/S

Power evacuation from Nyadi Hydro Power (NHP) and Khudi Hydro Power (KHP), to local consumer is possible with four outgoing feeders of 5 MVA, 33/11 Udipur substation. The four feeders are Besisahar, Bhoteodar, Okhari and MajhGau with total connected load (TCL) of 1050 kVA, 1950 kVA, 550 kVA and 450 kVA respectively. Load flow analysis of these feeders using Carl1.0 for peak load time gives the clear picture of local power flow.

43


The result of load flow analysis of each feeder is given below. Detail result is presented in Appendix F. Table.4.36: Load flow result of four feeders of Udipur S/S.

Feeder Name

Total

Total

Active

Reactive

Minimum

Conductor, km

Connected

Power fed

Power

Power

Voltage

Load

(kW)

Loss

Loss

(%)

Dog

Rabbit

Weasel

(kW)

(kVar)

(kVA)

Besisahar

1050

973.59

33.39

39.01

93.56

13.4

6.72

16.8

Bhoteodar

1950

1660

100.33

80.48

90.21

16.5

15.9

34.9

Okhari

550

443.68

3.68

2.08

98.9

0

9

18

MajhGau

450

388.39

5.89

3.33

97.38

0

12

20

Discussion:

From load flow analysis of four feeders it is found that feeder Bhoteodar is worst of all, having minimum voltage (at farthest end) of 90.21% and total feeder loss of 6.04%. This feeder uses 16.5 km of conductor 'dog', 15.9 km of conductor 'Rabbit' and 34.9 km of conductor 'Weasel'. To make local power evacuation more effective and efficient during peak loading, above four feeders should be managed in such a way so that some part of loads of feeders Besisahar and Bhoteodar should be shifted to Okhari and MajhGau feeder for better distribut ion system.

44

Chapter 5. Conclusion and Recommendation

CHAPTER 5

Conclusion and Recommendation For Power Evacuation study, 3.5 MW Khudi Hydro Power (KHP), 4.5 MW Lower Nyadi Hydro Power (LNHP) and 2 MW and Lower Khudi Hydro Power (LKHP) are selected from Lamjung district of Gandaki Zone in Western Nepal. In order to carry power evacuation study a program is developed in spread sheet. This program results in optimized conductor and voltage level. This spread sheet program is good only for such transmission line in which there is no addition of load in future. This program is used to study power evacuation from KHP, LNHP and LKHP. From Netbas Simulation system performance for different loading case is studied. KHP, LNHP and LKHP are located to the north of Udipur S/S. So, one switching station at Khudi which will be the meeting point of transmission lines from three small power plants is taken for study. From Khudi switching station to Udipur substation 14 km long transmission line is used. There are three more existing transmission line sections which are 20 km long Udipur-Dumre joining Udipur S/S and Damauli S/S, 14.5 km long Dumre-Damauli and 12 km long Dumre-AnbuKhaireni. All of these transmission line sections have conductor ‘Dog’ and charged at 33 kV. The power evacuated from KHP, LNHP and LKHP are evacuated to Udipur S/S, Dumre S/S, Anbu Khareni S/S and finally excess power is evacuated to grid at Damuli Substation. Existing System

The study shows that the existing system is good only for 50% of total substation capacity (6.75 MW) considering prescribed transmission loss (4%) and Voltage regulation (10%). It means the transmission margin is 6.75 MW for Damuli-Dumre transmission section using conductor ‘Dog’ at 33 kV system. For this section during 30% of total substation loading available transmission capacity is 2.45 MW. Changing the existing conductor ‘dog’ with ‘wolf’ the transmission margin can be increased to 11 MW. KHP Evacuation System

Power evacuation from KHP involves 0.9 km long transmission line from KHP to KSw/S and 14 km long transmission line from KSw/S to Udipur S/S. The 33 kV evacuating system with conductor ‘Dog’ results in 98.41 line efficiency and 2.16% voltage regulation. For KHP evacuation only 33 kV system with conductor ‘Wolf’ is best because it has lowest

45


NPV of Investment. At 100% substations load the voltage regulation and total transmission loss has improved. Use of 'wolf' conductor in new transmission section is recommended for better system performance. KHP and LNHP Evacuation System

Transmission line from LNHP (4.5 MW) is connected to KSw/S through 7 km long transmission line. For this section with conductor ‘Dog’ and 33 kV system voltage the line efficiency is 99.03 and voltage regulation is1.3. Conductor 'Panther' is found to be the best with lowest NPV of investment. Power generation from KHP and LNHP is 8 MW and this power is jointly evacuated from KSw/s to Udipur S/S. From spreadsheet analysis 66 kV system with conductor 'Panther' has lowest NPV of investment. But existing system is 33 kV so changing to 66 kV will not be feasible. In 33 kV system, conductor 'Lion' is found to be the best. As the existing system is using conductor 'dog' so the analysis using conductor 'dog' shows that in 100% substations load the total transmission loss is 5.15% and in 10% substations load the total transmission loss is 11.12%. NEA line (from Damauli S/S to Udipur S/S) has improved for 70% and above loading case but for load 50% and less system performance is worse because all the excess power has to be fed to Damauli S/S which 34.5 km away from Udipur S/S. For KHP and LNHP power evacuation 33 kV system with conductor 'Lion' is recommended. KHP, LNHP and LKHP Evacuation System

LKHP is only 0.5 km away from KSw/S so the 2 MW power generated will be transmitted to KSw/S and for this sectio n 33 kV system with conductor 'dog' is good. Now, in KSw/S power incoming from three power generating stations. From spreadsheet calculation in 33 kV transmission system conductor 'dog' is not good because of poor efficiency 95.85%. In 33 kV system conductor 'Bear' has lowest NPV of Investment and in 66 kV system conductor 'Panther' is best. KHP, LNHP, LKHP Evacuation System and Chame Load

Chame S/S is located in Manang district and 50 km away from KSw/S. To transmit power in 33 kV level conductor 'Beaver' is found to be the best option. Distribution planning of Udipur S/S

The above evacuation study shows that the system performance will be better if more power can be consumed locally so the planning upto distribution level is very important for best

46


local power evacuation. Load flow analysis of four feeders are carried out and it is found that feeder Bhoteodar is worst of all, having minimum voltage (at farthest end) of 90.21% and total feeder loss of 6.04 %. This feeder uses 16.5 km of conductor 'dog', 15.9 km of conductor 'Rabbit' and 34.9 km of conductor 'Weasel'. To make local power evacuation more effective and efficient during peak loading, above four feeders should be managed in such a way so that some part of loads in feeder Besisahar and Bhoteodar should be shifted to other feeder so that addition of new load centers can be done. Finally, the methodology adopted using computer programs for designing as well as studying the power evacuation from small hydro power plant is also useful for any other selected small hydro power plant in any remote area of Nepal.

47

nepal substations and loads

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