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TB 092 1995 SC 14 WG 14.03.02 DC side harmonics and filtering in HVDC transmission systems

The report deals with the harmonic voltages and currents of concern on the DC side of HVDC transmission systems. Its aim is to provide some guidance to both users and suppliers of HVDC links in such a way that a common understanding could be
established in the area of DC side harmonics and filtering.

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TABLE OF CONTENTS

1 INTRODUCTION

2 POTENTIAL EFFECTS OF HARMONICS

      2.1 General

      2.2 Interference with nearby telecommunication facilities

      2.3 Safety aspects

      2.4 Audible noise

      2.5 Potential adverse effects on dc-substation equipment

      2.6 Influence on ac-side equipment

            2.6.1 Harmonic AC/DC interaction penetrating through the converters

            2.6.2 AC/DC inductive coupling between AC and DC transmission lines

      2.7 Survey on countermeasures

            2.7.1 Countermeasures for the main circuit arrangement

            2.7.2 Countermeasures on the telecommunication circuits

3 INDUCTIVE COORDINATION AND CONSIDERATIONS ON COMPATIBILITY LEVELS

      3.1 Coupling mechanism

      3.2 Calculation methods

            3.2.1 Equivalent Disturbing Current Method (Ieq)

            3.2.2 Equivalent test line method

            3.2.3 Calculation of the mutual impedance

            3.2.4 Parameters for coupling impedance calculations

      3.3 Basic considerations on compatibility levels

            3.3.1 Values used for Ieq and INV

4 HARMONIC GENERATION, PROPAGATION AND MODELLING

      4.1 Introduction

      4.2 Harmonic voltage generation

      4.3 System modeling

            4.3.1 Calculation of Harmonic Driving Voltages

            4.3.2 Frequency range

            4.3.3 Converter representation

            4.3.4 HVDC line representation

            4.3.5 DC switchyard equipment representation

            4.3.6 Frequency and component deviations

      4.4 Harmonic current calculation

            4.4.1 Balanced bipolar operation

            4.4.2 Unbalanced bipolar operation

            4.4.3 Return path for ground mode currents

5. MITIGATION OF ADVERSE EFFECTS OF DC SIDE HARMONICS

      5.1 Introduction

            5.1.1 General

            5.1.2 Objectives of mitigation measures

            5.1.3 Optimization of cost of mitigation measures

            5.1.4 Mitigation measures in the HVDC system

            5.1.5 Back-to-back schemes

            5.1.6 Cable transmissions

      5.2 Mitigation measures in telecommunication systems

            5.2.1 Modification of existing equipment

            5.2.2 Modification of routing

            5.2.3 Replacement of open-wire lines by buried cable

            5.2.4 Carrier systems

            5.2.5 Optical fibre systems

      5.3 Filter performance

            5.3.1 Target limits for definition of performance

            5.3.2 Filtering mechanisms

            5.3.3 Example: long overhead line transmission

      5.4 Filter design

            5.4.1 Filter types and characteristics

            5.4.2 Arrangement and switching of filter banks

            5.4.3 Equipment rating for harmonic stresses

            5.4.4 Transient rating

            5.4.5 Rating for abnormal operation conditions

            5.4.6 Protection aspects

            5.4.7 Reliability and availability

            5.4.8 Audible noise

            5.4.9 Losses

            5.4.10 Seismic requirements

      5.5 Economic aspects

            5.5.1 General

            5.5.2 Equipment costs

            5.5.3 Indirect costs

      5.6 Future developments

            5.6.1 General

            5.6.2 Accurate specification of performance objectives

            5.6.3 Telecommunication technology

            5.6.4 Active DC filters

6 GUIDELINES FOR SPECIFICATION

      6.1 Introduction

      6.2 Circuit configurations and operating conditions

            6.2.1 Circuit Configurations

            6.2.2 Operating Modes

            6.2.3 Special Operating Conditions

            6.2.4 Range of Operating Parameters

      6.3 Basic data to be considered for harmonic calculation

            6.3.1 DC Transmission Line Data

            6.3.2 AC System Data

            6.3.3 Deviation of Parameters and Tolerances to be Considerer

      6.4 Methods for harmonic calculation

      6.5 Performance requirements

            6.5.1 Telecommunication Interference

            6.5.2 Other Items

      6.6 Dc side harmonic field measurements

      6.7 Criteria for filter design