The study considers the overall HVDC system economics, capital (lines and stations), losses, operation and maintenance. The most economically favorable voltages and conductor configurations are studied for several HVDC system alternatives. It is shown how the HVDC line and the converter stations selection impact each combination. Directives are presented on the 'best-solutions' for different sets of transmission parameters

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1 Introduction

2 Objectives

3 Overview of Configurations Studied

      3.1 Overview

      3.2 Configuration

            3.2.1 Transmission Line Configurations

            3.2.2 Converter Configurations

            3.2.3 System Configurations

            3.3 Cases Studied

4 Transmission Line Considerations

      4.1 Overvoltages

            4.1.1 Types of Overvoltages

            4.1.2 Determination of Switching Surge Overvoltage (Fault Application)


         Fault Application Phenomena

         Calculation Results

      4.2 Insulation Coordination

            4.2.1 Operating Voltage

         Air Clearances

         Number of Insulators

         Insulator String Swing Angle

            4.2.2 Clearances for Switching Surge Withstand

         Clearances for an Established Flashover Risk of Failure.

         Switching Overvoltages with Conductor Displacement due to Wind

         Composite Risk Calculation

      4.3 Pole Spacing Determination

            4.3.1 Case of I Strings

            4.3.2 Case of V strings

      4.4 Conductor Current Carrying Capability and Sags

            4.4.1 Current Capability

            4.4.2 Sag for Conductor Maximum Temperature

      4.5 Tower Height

      4.6 Lightning Performance

      4.7 Right-of-Way Requirements for Insulation

            4.7.1 Line with I Strings

            4.7.2 Line with V Strings

      4.8 Corona effects

            4.8.1 Concepts

         Conductor Surface Gradient

         Corona Loss

         Radio Interference and Audible Noise .

            4.8.2 Calculation Results

         Conductor and Shield Wires Surface Gradient

         Corona Losses

         Radio Interference and Audible Noise

      4.9 Ground-Level Electric Field and Ion Current

            4.9.1 Preliminary Design

            4.9.2 Further Considerations .

            4.9.3 Design Criteria

            4.9.4 Calculations for Existing Projects

      4.10 Mechanical Design

            4.10.1 Base Case

            4.10.2 Meteorological Conditions and Basic Stresses

         Region I

         Region II

            4.10.3 Sag and Tension Calculations

         General Conditions

         Conductor Configuration Alternatives and Wind Pressures


         Tower Families

            4.10.4 Loading Conditions

            4.10.5 Results of the Tower Weights

            4.10.6 Sensitivity Analysis

      4.11 Line Economics

            4.11.1 Line Costs Involved

            4.11.2 Transmission Line Costs

            4.11.3 Losses

            4.11.4 Operating and Maintenance Costs

            4.11.5 Interest During Construction

            4.11.6 Most Economical Conductor

5 Converter Station Cost Equation

      5.1 Cost Data

      5.2 Cost Equation

      5.3 Cost Support Information and Breakdown

      5.4 Converter Station Considerations.

            5.4.1 Introduction HVDC/FACTS

            5.4.2 Transport Limitation

            5.4.3 Station Losses


         Converter Valves

         Converter Transformers

         Smoothing Reactor

         AC filter Circuits and Capacitor Banks

         DC Filter Circuits

         Other Components of HVDC Stations

         Environmental Conditions

         Load Cases

         Practical Loss value

            5.4.4 Standard Thyristor Bipoles

         Layout and Single Line Diagram

         Power Range

            5.4.5 Cost Basis

         Primary Equipment

         Secondary Equipment

            5.4.6 Individual Design or Equipment

            5.4.7 Power Tap (T off)

6 Electrodes, Electrode Lines and Metallic Return

      6.1 Introduction

      6.2 Ground Return

      6.3 Metallic Return124

      6.4 Electrode Line Cost

      6.5 Electrode Line and Metallic Return Design

      6.6 Electrode Design and Costs

7 System Economics

      7.1 Introduction

      7.2 Components of the System Costs

            7.2.1 Transmission Lines

            7.2.2 Joule Losses

            7.2.3 Corona Losses

            7.2.4 Line Operating Cost and Interest During Construction

            7.2.5 Most Economical Conductor

            7.2.6 Converter Station Cost

      7.3 Simplified Calculation

            7.3.1 Base Case Results

            7.3.2 Sensitivity to Cost of Losses

            7.3.3 Evaluation of the Impacts

            7.3.4 Simplified Evaluation of the Impacts

            7.3.5 Further Considerations

      7.4 Calculations Considering Cost Components Allocated in Different Years (General Approach)

            7.4.1 Study Case 1: Basic Case

            7.4.2 Study Case 2: As Basic Case; P taking 4 years to reach 3,000MW

            7.4.3 Study Case 3: Power 6,000 MW; 2 x 600 kV or 1 x 800 kV

            7.4.4 Study Case 4: Power 6,000 MW; ±800 kV; series or parallel arrangement

8 Conclusions and Summary