.A. 
ANALYSIS OF 
BULK CONSUMER DEMAND 
FOR TARIFF DESIGN 
A dissertation submitted to the 
Department of Electrical Engineering, University of Moratuwa 
in partial fulfillment of the requirements for the 
Degree of Master of Science 
by 
D . H . G U N E R A T N E 
. 3 (( 3> V « r 
Supervised by: Prof. J.R. Lucas 
Dr. Tilak Siyambalapitiya 
University of Moratuwa 
100847 
Department of Electrical Engineering 
University of Moratuwa, Sri Lanka 
August 2011 
1 0 0 8 4 7 
r . 
DECLARATION 
The work submitted in this dissertation is the result of my own 
investigation, except where otherwise stated. 
\ It has not already been accepted for any degree, and is also not being 
concurrently submitted for any other degree. 
D.H.Guneratne 
Y 18 t h August 2011 
We endorse the declaration by the candidate. 
Prof. J.R. Lucas 
Dr. Tilak Siyambalapitiya 
i 
CONTENTS 
Declaration 
Abstract 
Acknowledgement 
List of figures 
List of tables ' 
List of Abbreviations 
Chapters 
1. Introduction 
1.1 Background 
1.2 Problem statement 
1.3 Objectives 
1.4 Methodology 
1.5 Motivation 
2 . Analysis of bulk consumer demand 
2.0 Load profile analysis 
2.1 A bulk consumer with a very low load factor 
2.2 A bulk consumer operating a night shift during system peak 
2.3 Continuous demand from morning to late night 
2.4 A poor power factor condition in a manufacturing industry 
2.5 A high load factor and a good power factor case 
2.6 Very high demand with a good power factor during a day shift 
3. Analysis of cumulative demand profiles 
3.1 Selection of the sample to analyze the collective demand 
3.2 Collective demand profile of the sample 
3.3 Collective active-power demand profile 
3.4 Collective reactive-power demand profile 
3.5 Power factor profile of the collective demand of the sample 
n 
4. Pricing of reactive power consumption 23 
4.0 Reactive power supply 23 
4.1 The point of reactive power supply 23 
4.1.1 Reactive power supplied from generation 23 
4.1.2 Reactive power supplied at substation level 24 
4.1.3 Reactive power generated at consumer end 24 
4.2 Pricing a unit of reactive energy 26 
4.2.1 Pricing a unit of kvarh if utility provides reactive power 26 
4.2.2 Pricing a unit of kvarh if the consumer generates reactive power 29 
4.3 Comparison of international charges 33 
5. Alteration to maximum demand charge 35 
5.1 Revision to M D charge if a reactive energy charge is imposed 35 
5.2 Effect to the monthly bill 37 
5.2.1 Application to real consumers 37 
5.2.2 Theoretical application for further analysis 37 
5.3 Maximum demand charge on a t ime of the day basis 39 
5.4 Classification of load profile of bulk consumers 39 
6. Conclusion and Recommendations 45 
References 46 
Appendix I Electronic digital meters with R M R facility 47 
Appendix II Awareness program 49 
Appendix III Comparison three part tariff (TOD) for energy 50 
Appendix IV Pricing kvarh unit for few consumers 52 
Appendix V Effect on monthly bill 60 
Abstract 
Bulk consumers are the main revenue generating category of the electricity consumer 
mix in Sri Lanka. Their contribution has a large impact on demand in the power 
distribution network. The tariff applied, the metering system and the analysis of their 
consumption is very important to the utility and to the consumer. 
Optimizing the resources in the power distribution network is very important to the 
utility. The utility has to encourage the consumer to manage the load scientifically. 
The energy consumed should be charged in a fair manner. Paying a reasonable bill is 
appreciated by any consumer. In this context, application of a 'cost reflective' tariff is 
fair by the consumer and the utility. As a country on the whole, it is an important 
attempt to utilize the energy in the most cost effective manner. This would help the 
country facing the energy crisis, sustain the industries and employment, and enhance 
the power quality and reliability. 
The objective of this research is to investigate individual and collective demand 
profiles of bulk consumers, and to encourage them to implement demand management 
measures. This is done by introducing a better cost reflective tariff. Thereby, both the 
consumer and the utility would be benefited. 
Electronic digital meters, with remote meter reading facility, were introduced very 
recently. These meters provide detailed information about the consumer's demand 
profile and give an in-depth view of their electricity consumption. Studying these 
demand profiles show that there are many consumers with a poor power factor, 
consuming a large amount of reactive power from the system, transmitted all the way 
from the point of generation. This causes excessive burdens on the network for 
handling extra current and causing excessive power and energy losses. 
In this research, an effective sample of bulk consumers who consume a large amount 
of reactive power is considered. In order to encourage them to improve their power 
factor, it is suggested to introduce a charge for reactive power consumption (in 
Rs/kvarh). Considering a sample, the price of a unit of reactive energy is calculated 
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based on, if the utility does the power factor correction and if the consumer does the 
correction. It will be shown that, it is more appropriate for the consumer to do the 
power factor correction on their own. This suggested charge is much reasonable to 
both the utility and the consumer. A charge for the consumption of reactive power 
would be cost reflective and would reward high power factor consumers by giving a 
lower max imum demand charge. Thereby, the consumers with a poor power factor are 
encouraged to improve their power factor. With this enhancement to the tariff, both 
the utility and the consumer will be benefited. 
The max imum demand charge is imposed to reduce the demand of system in general. 
However, it does not deal the issues of low power factor, in a cost reflective manner. 
It is also imposed, to compel the consumer to manage his demand-peaks as much as 
possible. Both these components contribute to the max imum demand charge. By 
removing the power factor contribution from the presently applied ' M a x i m u m 
Demand ' charge, the demand-peak component can be isolated. Thus, the new 
maximum demand charge would inevitably become a lesser charge. 
The demand-peak component is a burden to the utility during the system peak period. 
During the off peak period, these individual demand-peaks will not cause much 
difficulty to the utility to cope up with. Therefore, it should be applied on a t ime of 
day basis. It is reasonable to apply a lesser charge (as an incentive) during off-peak, 
and a higher charge during peak load t ime period. Thereby, the bulk consumers are 
encouraged to shift on to off peak t ime. This enhanced tariff structure would benefit 
both the consumer and the utility. 
The study concludes by suggesting a charge for the monthly reactive energy 
consumption, while recommending a reduction in the present max imum demand 
charge. Further, the bulk consumers are categorized into five types, based on their 
demand profile. These may be used in extending the study to design a max imum 
demand charge base on time of day. 
Acknowledgement 
I wish to thank my supervisors, Professor J.R.Lucas and Dr.Tilak Siyambalapitiya, for 
their great insight perspectives, guidance and concern towards my research. My 
sincere thanks go to the M.Sc. course coordinator Professor Ranjith Perera, for 
helping in various ways for my academic work with cooperation and guidance. My 
sincere gratitude is also extended to the staff in the Department of Electrical 
Engineering, in the Faculty offices, in the Library and others in the university. 
My sincere gratitude goes to Mr.U.K.W. Silva (Deputy General Manager, PHM-R4) 
and Mr.M.M.M.Sabry (Chief Engineer, PHM-R4) , under whom I serve at the C.E.B. I 
extend my thanks to Mr.P.I.A.S.Perera, (Chief Engineer, Area office Ratmalana) , 
Mr.M.D.P.R.Gunati lake (Electrical Engineer, Meter Testing Laboratory R4), 
Mr.B.M.A.T.Priyadarshana (Project Engineer R4). 
It is my duty to thank many individuals, friends and colleagues who have not been 
mentioned here personally in making this research study a success. 
It is my pleasure to remember the kind co-operation extended by the colleagues in the 
post graduate programme, my parents and specially my wife who helped me to 
continue the studies up to the end. 
vi 
List of Figures 
Figure Description Page 
2.1 (a) Daily demand profile of a toy factory 8 
2.1 (b) Weekly demand profile the toy factory 9 
2.1 (c) Monthly demand profile the toy factory 9 
2.2 Demand profile of a cable manufacturer 10 
2.3 Demand profile of a super market in Ratmalana 11 
2.4 (a) Daily demand profile of a tools and dies manufacturer 12 
2.4 (b) Power factor profile of the tools and dies manufacturer 12 
2.5 (a) Demand profile of a food producer 14 
2.5 (b) Power factor profile of the food producer. 14 
2.6 (a) Demand profile of a garment factory in Ratmalana 16 
2.6 (b) Power factor profile of the garment factory 16 
3.2 Collective demand profile for 105 bulk consumers 18 
3.3 Collective active power demand profile of 105 consumers 19 
3.4 Collective reactive power demand profile of 105 consumers 20 
3.5 (a) Collective power factor profile of 105 bulk consumers 21 
3.5 (b) Power triangle for the collective load of 105 bulk consumers 22 
4.1.1 Line diagram of reactive power supplied from generation 23 
4.1.2 Line diagram of reactive power supplied at substation 24 
4.1.3 Line diagram of reactive power generated at consumer level 25 
4.2 (a) Reactive power supplied at substation level for 105 consumers 26 
4.2 (b) Line diagram of reactive power supplied at substation 26 
4.2 (c) Reactive power demand profile of collective load 27 
4.2.2 (a) Load profile of an apparel industry 30 
4.2.2 (b) Power factor profile of the apparel industry 30 
4.2.2 (c) Reactive power demand profile of the apparel industry 30 
4.2.3 Power triangle for an ideal load 33 
5.2.2 Effect to the monthly bill 38 
5.4.1 Type 1 load profile model 40 
5.4.2 Type 2 load profile model 41 
5.4.3 Type 3 load profile model 42 
5.4.4 Type 4 load profile model 43 
vii 
List of Tables 
Table Description Page 
4.2 kvarh unit costs for five cases in the sample 32 
4.3 Comparison of international prices for a kvarh unit 34 
5.2 Comparison of the existing tariff and the proposed tariff 36 
Al (a) Tariff for active power 45 
Al (b) Comparison of time of the day tariff for energy 46 
List of Abbreviations 
RMR Remote Meter Reading 
PPM Programmable Poly Phase Meters 
BSC Bulk Supply Consumers 
MD Maximum Demand 
viii