Line Loss Analysis and Calculation of Electric Power Systems
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Line Loss Analysis and Calculation of Electric Power Systems

Line Loss Analysis and Calculation of Electric Power Systems by Anguan Wu and Baoshan Ni | PDF Free Download.

Analysis and Calculation of Electric Power Systems Contents

  • Overview
  • Calculation of Line Loss by Current Load Curve
  • Probability Theory Analysis of Current Load Curve
  • Calculation of Line Loss by Power Load Curve
  • Line Loss Calculation after Reactive Compensation
  • Change Law for the Electric Energy Losses of Power Grids 
  • Analysis and Control of Line Loss Rate Indicators of Power Grids
  • Theoretical Calculation of Electric Energy Losses of Power Grid Units
  • Calculation of Electric Energy Losses of Multi-branch Lines
  • Calculation of High-voltage Power Grid Losses
  • Analysis and Calculation of Loss Allocation
  • Technical Measures for the Reduction of Line Losses
  • Line Loss Prediction and Loss Reduction Plan for Power Grids
  • Analysis of the Influence of Power Grid Line Losses on Power Grid Enterprises
  • Management and Utilization of Line Loss Mass Information for an Electric Power System

Preface to Line Loss Analysis and Calculation of Electric Power Systems

It has been over a decade since the Chinese publication of Line Loss in Electric Power Systems. To keep pace with technological developments, I started a revision as early as 2002,

following the main principles that the theoretical framework and characteristics of the first edition should be retained, with new contents added according to new problems after the reform of electric power systems and the new requirements for line loss management practices and in combination with practical experience.

The theoretical framework of the first edition used the loss factor method as the mainline and the quadratic trinomial ΔA = B + CA2 as the subline.

The random test method was used to verify the wide applicability and validity of the load factor formula put forward by Liu Yingkuan, a Chinese scholar. The equivalent load curve method was extended and expanded.

The line loss calculation curve was given for various designs of voltage class lines. The conditions at which the minimum line loss rate was achieved were set out.

The relationship between the load loss coefficient and six variables was demonstrated by using the concept of the loss factor of the equivalent load curve.

The inherent law between the electricity line loss and the electric supply change was analyzed, and then the electricity line loss prediction formula was put forward. The concept of marginal line loss rate was first introduced, and based on this, the optimal distribution of electric supply was proposed.

The first edition provided and compared several methods of theoretical calculation of line loss in a multi-branch distribution network.

As the construction of smart distribution networks is being vigorously promoted today, these methods provide multiple choices for the intelligent calculation and control of line loss in the distribution network.

The first edition comprehensively explained the technical measures of loss reduction. In addition, this book gives many examples to help readers understand the content and refer to this book during their work.

Maintaining the theoretical system of the first edition, this revision makes small adjustments to the sequence of chapters and supplements these with new content.

The second edition contains 15 chapters as compared to 10 chapters in the first edition, and 36 examples as compared to 27 in the first edition.

The title of the revision is changed to Analysis and Calculation of Line Loss in Electric Power Systems which is more consistent with the contents of this book. This revision mainly includes the following supplementary contents:

1. The maximum, normal, and minimum modes are classified from the perspective of probability. The calculation formulas of the three section power point of division and the electric supply are given, to provide a new way to analyze load prediction, loss prediction, or time of use electricity pricing by considering changes of the three modes (Section 3.4 in Chapter 3).

2. A chapter is specially provided to explain the calculation of loss in high-voltage power grids. Various calculation methods of loss in high-voltage power grids are compared, and a new calculation method based on the three mode section division is put forward (Chapter 10).

3. The essence of loss allocation is elaborated by a simple power supply model. A new method of interprovincial loss allocation within the regional network is created with a marginal loss electricity price (the product of marginal line loss rate and transmission price) as the economic signal.

The Shapley value method and the generation quantity multiplier method used in California are introduced regarding the calculation of reasonable loss allocation between high-voltage customers, both direct supply and under a complex trading mode. The example of calculating the loss allocation in a five node power network is given (Chapter 11).

4. The prediction of electricity line loss and line loss rate in power grids and loss reduction plans are introduced. On the basis of the prediction formula of electricity line loss set out in the first edition, the prediction formula of line loss rate is added, and the requirements and preparation methods for loss reduction plans are introduced (Chapter 13).

5. The cost–volume–profit analysis model for power grid enterprises is established. The balance between electricity flow and capital flow among main production links within power grid enterprises is analyzed.

The model of link cost and link electricity price within power grid enterprises is put forward, which satisfies the lean management requirements of these enterprises (Sections 14.1 and 14.2).

6. To control both the direct supply electricity price for high-voltage customers and the sales electricity price for low-voltage customers, the multi-section electricity price model is established by taking the line loss effect into account.

The underlying cause of implementing the coal–electricity price linkage in China is explained. The double component ratio coefficient is used to build the coal–electricity price linkage model, to provide a quantitative analysis method to control the on-grid price level (Sections 14.3 and 14.4).

7. The method of analysis of price markup at the power sales end is studied, to provide conditions for completely assessing the production benefits of a transmission and transformation project during the post-project assessment (Section 14.5).

8. The current application situations of integrating loss mass information with other information are introduced. The integration of line loss information with other information and the use of this integrated information for control of voltage quality are explained.

To realize the utilization of mass information on line loss, the design concepts of relevant data warehouse and data mining are introduced (Chapter 15).

Many of the above contents have been published in national professional meetings or magazines, and some contents are published first in this revision. I hope that years of my thoughts and accumulated experience can benefit readers who focus on such issues.

When revising this book, I was counseled and encouraged by Professor Liu Qingguo of North China Electric Power University and supported and helped by upperclassman Jin Wenlong. Some contents of this revision were reviewed by Zhang Zuping, Senior Engineer of China Electric Power Research Institute, who proposed many valuable suggestions.

Zhang Youmin of Shanxi Electric Power Exploration and Design Institute provided full support to the proof calculation of the three mode section division.

I, hereby, would like to express my heartfelt thanks to all my teachers, upperclassmen, and peers for their sincere help. As entrusted by my teacher Ni Baoshan and thanks to the help of everybody, this revision is finally submitted for publication.

Although Teacher Ni, who guided and coauthored this revision, has passed away and was unable to witness this result by himself, I can console my teacher as I have made all efforts to academically pass on the knowledge to a new generation.

Due to the limitation of my level of knowledge, this book may have some inaccuracies and areas for improvement. Readers are invited to comment and correct. 

Foreword to Line Loss Analysis and Calculation of Electric Power Systems

Energy-saving and consumption reduction in the electric power system are important tasks to which generations of people have always paid attention and been committed.

In recent years, I heard that several aspiring experts have been summarizing and writing (revising) works or papers based on their working practices in line loss.

A few days ago, Wu Anquan told me that he had finished the revision of the second edition of Analysis and Calculation of Line Loss in Electric Power Systems (hereinafter referred to as Line Loss) and asked me to write a foreword for this second edition.

I felt happy that new results were created against new challenges, and also afraid that my words could not express my thoughts.

However, as I wanted to live up to an old friend’s sincerity, I pleasantly promised to have a try, taking this opportunity to focus on loss reduction in power grids and to express my respect for line loss workers.

I was filled with emotion when looking back on my participation in the line loss business, recalling the benefits I gained from the revision and review of the line loss management guidelines (provisions) and the loss reduction plans of the State Grid Corporation of China, and reading Wu’s second edition of Line Loss and his papers published in recent years.

Over the past 30 years since the reform and opening-up policy, China has implemented both energy development and savings, promoting the rapid development and increasing the benefits of the electric power system.

As of 2011, the installed power-generating capacity has ranked second in the world for consecutive years, and the size of power grids and the total electricity consumption nationwide have ranked first in the world.

The economic efficiency of the electric power industry was significantly improved: the average electric supply coal consumption rate of coal-fired units reached 330 g/(kW∙h), and some large units even realized a coal consumption rate of 300 g/(kW∙h);

the electric supply line loss rate in power grids was 6.39% nationwide, and even maintained 5.5% or below in some provinces and cities; and overall, the line loss rate was at an internationally advanced level.

Looking back to the progress of power grid loss reduction in China after the reform and opening-up, the first 20 years saw a remarkable reduction of line loss rate from 9.64% in 1978 to 7.81% in 2000, but the curve of the annual line loss rate revealed several saddle-shaped fluctuations, showing that loss reduction was still difficult.

During the first 12 years of the new century, with progress in science, technology, and equipment, especially strengthened line loss management, the line loss rate kept a steady decline without any big fluctuation and was reduced by 1.42% in 2011 over 2000.

Based on the size of the electric supply in 2010, if the line loss rate was reduced by 1%, equal to an annual electric loss reduction of about 42 × 1012 kW∙h, then over 13.8 × 106 t of coal was saved each year and over 27.6 × 106 t of carbon emissions were reduced, marking a great achievement in energy conservation and emission reduction.

Due to my personal experiences, I pay close attention to and feel delighted with each year’s new achievements in the loss reduction in power grids. I deeply respect the technicians and managers engaged in the loss reduction for their steadfast and diligent professional ethics.

These remarkable achievements in the reduction of loss in power grids are mainly attributable to improvements in the theoretical analysis and calculation of line loss, the implementation of loss reduction technologies and measures, and effective policy management, as well as the assiduous efforts of relevant personnel.

Since the 1980s, many professors, scientific and technical personnel, and business personnel working in the frontline of power grid enterprises, who were engaged in theoretical research into power grid line loss and in practical analysis and calculation, have worked hard and closely with each other.

They have made outstanding contributions to the promotion of the theoretical research, analysis, and calculation of line loss in China, the implementation of loss reduction measures and technical management, and the realization of a continuous and steady decline in the line loss rate.

In the 1980s, Zhejiang University and Nanjing Administration of Power Supply cooperated in preparing Theoretical Calculation of Line Loss and Technical Measures of Loss Reduction (written by Professor Ni Baoshan);

Professor Yang Xiutai of Chongqing University compiled Theoretical Calculation and Analysis of Line Loss in Power Grids; Wu Anquan (Senior Engineer of Taiyuan Administration of Power Supply) and Professor Ni Baoshan coauthored Line Loss in Electric Power System (1996);

Yu Zhongian (Senior Engineer of Jiangsu Electric Power Company) and Professor Chen Xingying of Hohai University wrote Electric Energy Loss in Power Grids (2000). They studied, learned, and introduced the theoretical results of Europe, America, and the former Soviet Union in the calculation of line loss in the electric power system.

Based on the actual situations of power grids in China, they discussed and proposed many methods for the theoretical calculation of line loss, and promoted the application of microcomputers in the calculation of line loss.

In addition, they participated in many seminars, exchange meetings, and information sessions, making good technical preparations and doing real work for the formulation of line loss calculation guidelines, line loss management provisions, and other industrial standards or corporate regulations, both for training in line loss management and reviewing loss reduction plans.

Their efforts have had an enduring influence on the theoretical calculation of line loss by power grid enterprises, the preparation of loss reduction plans, and improvements in the technical management of line loss in power grid enterprises.

Meanwhile, the national competent authority and the State Grid Corporation of China, by following the scientific development perspective and adhering to the energy development and conservation policy, worked together to promote an industry-university–research cooperation, to formulate, propagate, and implement regulations and guidelines, to take effective input and technical measures, and to play an organizational leadership and regulatory role.

This is an important reason why great achievements have been made in loss reduction for so many years, and an experience that should be learned. Since the twenty-first century, power grids have developed fast in China, with a continuously expanded size, more complicated network, and personnel increase or turnover.

In addition, China has boosted the development and utilization of renewable energy sources, and the electricity market is increasingly growing.

All of these developments and changes have posed new challenges to the objective of line loss management and loss reduction.

Therefore, even after his retirement, the author of this book, with diligent study and tireless exploration, was still dedicated to the work of line loss and spent over eight years in making this new achievement.

In the second revision of Line Loss, the author retained or improved the basic knowledge and methods of theoretical calculation of line loss from the first edition, such as the line loss calculation considering power factor, the concept of load loss coefficient,

the change rule of line loss, the methods of calculating line loss in loss calculation units and multi-branch lines, the methods of prediction of electricity line loss and line loss rate, and the principles of the optimal distribution of electric supply.

New additions in this revision include the calculation of loss in complicated power grids, the link electricity price, the balance between electricity flow and capital flow within power grid enterprises, the analysis of coal-electricity price linkage, and the utilization of mass information in line loss.

In addition, new results are theoretically explored and presented in terms of the three-section division of the load curve, the loss calculation and loss allocation in complicated power grids, and the composition and application of a multi-section electricity price.

Real analysis and calculation cases or parameters are also selected and provided. These studies and results are instructive when focusing on energy conservation and loss reduction against the backdrop of a market-oriented economy, and when seeking ways to improve benefits by power grid enterprises.

Wu Anquan and I are schoolmates, and we exchanged and cooperated much with each other on the line loss in power grids after the 1990s.

Wu studies hard, assiduously, and ambitiously, and has always been keen on the professional theories of line loss and the practical application of research.

Despite being over 60, Wu tirelessly writes papers and makes friends with others for sharing and improvement, which I respect very much. I sincerely recommend the second edition of Line Loss and believe that it will be conducive to professionals and college students involved in line loss management practices.

I hope that more young scholars can constantly dig into the ancient but young subject of “line loss”, to help resolve many complicated technical and economic problems arising from electricity marketization and the accessibility of renewable energy sources to the network.

Witnessing the development of line loss management in China, I would like to take this opportunity to share my thoughts and experiences with all young scholars.

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