Line Loss Analysis and Calculation of Electric Power Systems

Anguan Wu, Baoshan Ni

• Publisher: Wiley
• Year: 2015
• ISBN:
  9781118867235
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Power Resources
• Index: Technology & Engineering

Presents the fundamentals and calculation of transmission line losses, their reduction, and economic implications • Written by a very experienced expert in this field
• Introduces various technical measures for loss reduction, and appended with a large number of examples
• Offers a progressive and systematic approach to various aspects of the problems
• A timely and original book to meet the challenges of power and grid industry development

1
Overview

1.1 Active Power Loss and Electric Energy Loss

In an electric supply area, electric energy is supplied to customers through transmission, substation, and power grid distribution. During the transmission and distribution of electric energy, a certain quantity of active power loss and electric energy loss will be generated in all units of the power grids.

1.1.1 Main Types of Active Power Loss

According to the analysis based on electromagnetic field theory, the energy of an electromagnetic field is transmitted from the power source to the loads through the dielectric space of the electromagnetic field, and wires lead the energy of the electromagnetic field. The electric energy loss that goes into the wires and is then converted into heat energy is also supplied by the electromagnetic field.

According to the results of the analysis of a single core coaxial cable by using the Poynting vector of energy flow density in the case of AC transmission, while power is needed to transmit loads in the dielectric space, four types of active power loss are produced in the cable:

1. Resistance heat loss ∆P₁ (W)
   This is in direct proportion to the square of current, that is
   (1.1)

   
   Wherein:
   • I – current passing the cable core (A);
   • R – the sum of resistance of both the cable core and tegmen (Ω).
2. Leakage loss ∆P₂ (W)
   This is in direct proportion to the square of voltage, that is
   (1.2)

   
   (1.3)

   
   Wherein:
   • U – voltage between the cable core and tegmen (V);
   • G – leakage conductance of dielectric (1/Ω);
   • r – conductivity [1/(Ω∙m)];
   • l – length of the cable (m);
   • r₁ – radius of the cable core (cm);
   • r₂ – inside radius of the cable tegmen (cm).
3. Dielectric magnetizing loss ∆P₃ (W)
   This is in direct proportion to the square of current and the frequency, that is
   (1.4)

   
   (1.5)

   
   Wherein:
   • ω – AC angular frequency (1/s);
   • L – inductance of the cable (Wb/A);
   • μ – magnetic conductivity of the cable dielectric (Ω∙s/m);
   • tanδ – repeated magnetizing loss tangent of the cable dielectric.
4. Dielectric polarization loss ∆P₄ (W)
   This is in direct proportion to the square of voltage and the frequency, that is
   (1.6)

   
   (1.7)

   
   Wherein:
   • C – capacitance of the cable (F);
   • ε – dielectric constant of the cable dielectric (F/m);
   • tanδ – repeated magnetizing loss tangent of the cable dielectric.

The above four types of active power loss represent the basic types of active power loss in the electric power system. In addition, corona loss may occur in high-voltage lines and high-voltage motors. This is a special type of active power loss caused by ionization of dielectric particles outside a conductor when the electric field intensity is too high in the surface of the conductor. It is related to the surface field intensity of the conductor and the air density. See Chapter 8, Section 8.2 for details.

1.1.2 Calculation of Electric Energy Loss

Electric energy loss ∆A (kW∙h) is the integral of active power loss to time within a period, that is

(1.8)

For resistance heat loss, Formula (1.8) can be rewritten to

(1.9)

Within the period T, the load current and conductor resistance may va...

Table of contents

• Cover
• Title Page
• Table of Contents
• Foreword
• Preface
• Introduction
• 1 Overview
• 2 Calculation of Line Loss by Current Load Curve
• 3 Probability Theory Analysis of Current Load Curve
• 4 Calculation of Line Loss by Power Load Curve
• 5 Line Loss Calculation after Reactive Compensation
• 6 Change Law for the Electric Energy Losses of Power Grids
• 7 Analysis and Control of Line Loss Rate Indicators of Power Grids
• 8 Theoretical Calculation of Electric Energy Losses of Power Grid Units
• 9 Calculation of Electric Energy Losses of Multi-branch Lines
• 10 Calculation of High-voltage Power Grid Losses
• 11 Analysis and Calculation of Loss Allocation
• 12 Technical Measures for the Reduction of Line Losses
• 13 Line Loss Prediction and Loss Reduction Plan for Power Grids
• 14 Analysis of the Influence of Power Grid Line Losses on Power Grid Enterprises
• 15 Management and Utilization of Line Loss Mass Information for an Electric Power System
• Appendix A Calculation Curve of Corona Loss Power ΔPcor
• Appendix B Calculation of Electrical Parameters of Power Grid Units
• Appendix C Derivation of Loss Factor Formula by Subsection Integration Method
• Appendix D Actual Measurement Analysis of No-load Power Losses and Relationship between No-load Current and Voltage of Distribution Transformers
• References
• Index
• End User License Agreement