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Power Quality Training Courses

Compensation of reactive power, Voltage and current unbalance

LPQIVES is co-finaced by:

LPQIVES is a programme of:

LPQI is part of:

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Module 8 Compensation of reactive power, Voltage and current unbalance

1 INTRODUCTION Reactive power control, which is the theme of this seminar, has grown in importance for a number of reasons. First, the requirement for more efficient operation of power systems has increased with the price of fuels. Second, the requirement for a high quality of supply has increased because of the increasing use of electronic equipment and because of the growth in continuous-process industries.

1.1 General aims Because of the fundamental importance of reactive power control this seminar should appeal to a broad cross section of electrical, electronics, and control professionals. Practising engineers in the utility industry, and in industrial plants can find both the theory and the description of the reactive power control equipment invaluable in solving problems in power-factor correction (from the simple power-factor correction capacitor used with a single inductive load, to the sophisticated algorithms in Static VAR compensators), voltage control/stabilization, and phase balancing. The subject of reactive power control is closely connected with the subject of harmonics, because reactive power compensation and control is often required in connection with loads which are also sources of harmonics. It is important that compensation systems be deployed in such a way as to avoid problems with harmonic resonances. On of the session deals with these matters and includes a treatment of filters with practical examples. 1.2 Target groups This module’s target group are mainly: − end-users of equipment; − designers; − installers or contractor of installations; − electric networks operators; − equipment sellers and services providers in the electricity sector.

2 SPECIFIC AIMS AND TOPICS The pathway of learning consists of a 2 days course, subdivided in sections (with different duration), with these contents and related aims.

Contents

Aims

Contents

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1st day Power theories in electrical circuits, Capacitor banks and reactive power supply, power factor correction, Capacitor ratings, Harmonic amplification, Resonance (series and parallel), Capacitor arrangements and protection, Capacitor switching process, harmonic elimination, harmonic filters, voltage support, Series compensation The first day lessons aim to provide the user the basic knowledge about power capacitors and power factor correction, and about harmonics filtering 2nd day Rotating compensator (synchronous motor), Static VAR compensators, Automated controls, TSC, FC/TCR, STATCOM, Voltage/current unsymmetry, Description of the phenomenon, definitions, sources of the unbalance, Effects of the unbalance, Principle of

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symmetrization Improving symmetry in supply networks, Limit values, Methods for calculation and measurement of unbalance factors, Calculation of the unbalance factor, Principles of measurement , Assessment of equipment immunity The first day lessons aim to provide the user the basic knowledge about static and rotating compensators, and about voltage and current unbalance related issues. Use of the obtained knowledge to analysis and solving problems related to the topics.

Aims

Below there’s a detailed overview of the course contents. 2.1

Pathway of learning flow chart

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Time progression (hours)

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COURSE DETAILED PROGRAM

First day:

60 mins www.lpqi.org

Participants registration 3

5 mins 60 mins

Openning, informations, course introduction, course introduction Section 1:

Power theories in electrical circuits Modality: Lesson and discussion

60 mins

POWER CAPACITORS AND THEIR APPLICATION − Capacitor banks and reactive power supply, power factor correction − Capacitor ratings − Harmonic amplification − Resonance (series and parallel) − Capacitor arrangements and protection Modality: Lesson and discussion

15 mins

Coffee Break

60 mins

Section 2:

CAPACITOR SWITCHING PROCESS Modality: Lesson and discussion

Section 3:

HARMONICS ELIMINATION, HARMONIC FILTERS − Series-tuned filters − Double band-pass filters − Damped filters − Detuned (anti-resonant) filters − An example of harmonic filter design Modality: Lesson and discussion

Second day: 60 mins

30 mins

VOLTAGE SUPPORT Series compensation Modality: Lesson and practical training

15 mins

Coffee Break

60 mins

Section 4:

Rotating compensator (synchronous motor) − Static VAR compensators − Automated controls − TSC − FC/TCR − STATCOM Modality: Lesson and discussion

60 mins

Section 5:

VOLTAGE/CURRENT UNBALANCE − Description of the phenomenon, definitions − Sources of the unbalance − Effects of the unbalance Modality: Lesson and discussion

15 mins 45 mins

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Coffee Break Section 6:

Principle of symmetrization − Improving symmetry in supply networks 4

− Limit values Modality: Lesson and discussion 60 mins

Methods for calculation and measurement of unbalance factors − Calculation of the unbalance factor − Principles of measurement − Assessment of equipment immunity − Unbalanced loads - case analysis Modality: Lesson and practical training

45 mins

Final discussion and conclusions End of the course - user satisfaction survey (user’s questionnaire) Confirmations of attendance

4 − − − −

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GENERAL NOTES each day there will be two coffee breaks according to the seminar program; at the beginning of the course the lecturer will explain course aims and at the end he will verify their fulfilment; the course will be divided in theoretical and practical sections; at the end of the lessons, a user satisfaction survey will help the lecturer in monitoring the course quality.

TEACHING METHODS

Teaching methods are summarized in three main moments: − − −

knowledge transfer (Lesson) topics exposure by the lecturer with the help of slides and presentation of practical cases; deepening/learning verification (Discussion) general discussion stimulated by the lecturer (also during the lesson) to verify knowledge transfer; practical training, laboratory activities; group work

During all the sections, the lecturer will always attend, with teaching and/or activity coordination duty.

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DIDACTIC MATERIAL AND TOOLS

The didactic tools which will be used by the lecturers will be: − Blackboard − Video-projector − Notebook − Microphone The lecture room will be suitable to allow the use of all the above listed didactic tools and to enable group work for the attendants. Each user will receive, during the registration, a folder containing: − course program; − lecture notes containing all or part of the lecture slides; www.lpqi.org

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−

LPQIVES knowledge database access personal key.

All this didactic material, and eventually some additional electronic tools, will be available also in electronic format at: http://lpqi.org/custom/1036/. The folder will also include a user satisfaction questionnaire and a knowledge test (which will be both filled and submitted at the end of the course).

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EXISTING KNOWLEDGE REQUIREMENTS

The following (on the basic level) shall be prerequisite for the participant: − − − − −

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electric circuits theory: AC circuits; electric machines; electric power engineering; power system; power electronics; electric metrology.

ACQUIRED COURSE KNOWLEDGE

The knowledge acquired during the course should be sufficient for: − − − −

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design of capacitor bank used for power-factor correction, voltage control/stabilization, and phase balancing; elimination the over- current and over-voltages during the capacitor switching process; design of passive harmonic filters ; proposing other compensation systems.

ANNEXES - MIDAS REPORT

Press 1. PR-00007, Heydt, G, Power Quality Engineering, JEEE, Sep 2001 Encompassing most areas of electric power engineering, from generation to utilization, power quality engineering has been a topic of interest from the inception or the power engineering field. Here, the author describes how some contemporary factors have made it the subject of more focused interest

Publication 2. REP-00002, 2004, 1-9 Power Quality Glossary, Application note The glossary of main technical terms used in PQ

3. REP-00024, 2003, 5-3-6 Mitigation of voltage unbalance, Application Note Unbalance standards, limits, symmetrization - examples (calculations) Subjects: - Standardization - Principles of compensation and symmetrization - Static compensators

4. REP-00038, 2003, 3-1-2 Capacitors in Harmonic Rich Environments, Application note Inductances and capacitances. Reactive power. Why compensate? Central, disperssed compensation, detuning (in series with reactors)

5. REP-00047, 2003, 5-1-3 Introduction to Unbalance, Application note Background. Limits. Consequences. Mitigation

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6. REP-00069, 2003, Analysis of neutral conductor current in a three phase supplied network with non linear single phase loads, Application note This paper describes the effect of harmonics and unbalanced power supply and load on the current in the neutral conductor. Results from measurements are discussed.

7. REP-00071, 2003, On line monitoring of the neutral conductor current in a three phase supplied network with non linear load for different power supply and load conditions, Application note This paper describes the effect of harmonics and unbalanced power supply and load on the current in the neutral conductor. Measurement results are discussed. Using a programmable power source, arbitrary voltage waveforms are generated, independently for each phase. Each phase is loaded by non-linear loads. Phase currents and the current in the neutral conductor are analyzed for different configurations.

8. REP-00102, 2003, Control equipment for MV capacitor banks - ect 142, Application note Reactive energy compensation, switching capacitor banks, problems and solutions concerning capacitors, problems and solutions concerning switchgear, inrush-current calculations and surge inductances.

9. REP-00106, 2003, Power factor correction and its pitfalls. Application note no. 2, Application note Power-factor correction - subjects: 1. Basics of power-factor correction 2. Power factor of an installation having distorting loads 3. Harmonic distortion 4. Overloading of power-factor correction capacitors in the presence of harmonic currents 5. Power-factor correction capacitors and harmonic resonance 6. Detuning the power-factor correction capacitors

10. REP-00111, 2003, Voltage unbalance. Technical Note no. 6, Application note Voltage unbalance - subjects: 1. Introduction 2. Definitions of voltage unbalance 3. Effects of voltage unbalance on induction motors 4. Effects of voltage unbalance on AC variable speed drive systems 5. Mitigation of voltage unbalance and its effects

11. REP-00125, 2002, Specification guidelines to improve power quality immunity and reduce plant operating costs, Paper There are many useful IEEE and IEC standards that support the design of chemical and petrochemical plants. This article brings relevant Power Quality standards information together and provides recommendations in areas not yet covered in current standards. Circuit configurations for cost saving solutions are provided.

12. REP-00144, 1996, Guide to quality of electrical supply for industrial installations. PART 1: Types of disturbances and relevant standards, Brochure (Document available in the library of Katholieke Universiteit Leuven) 1. Scope 2. Introduction to the concept of electromagnetic compatibility (EMC) 2.1. Definition of EMC 2.2. Basic concepts 2.3. Compatibility, emission and immunity levels 2.4. The concept of electromagnetic environment 3. Types of disturbances, origins and effects 3.1. General classification 3.2. Harmonics 3.3. Interharmonics 3.4. Voltage fluctuations 3.5. Voltage dips and short (supply) interruptions 3.6. Voltage unbalance - asymmetry 3.7. Power frequency variations 3.8. Transient overvoltages 3.9. Mains siganlling www.lpqi.org

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3.10. Reference to HF conducted and LF and HF radiated disturbances 4. Coordination strategies among the involved parties 4.1. Evaluation of the disturbance emission level 4.2. Immunity of equipment 4.3. Mitigation techniques 4.4. Prediction studies for installation requirements 4.5. An approach to measurement criteria 5. Main standards and othter EMC publications 5.1. Recent developments in the approach to evaluating EMC coordination 5.2. Relevant EMC standards on EMC 5.3. CENELEC and national EMC standards and publications 5.4. Relevant publication from other international bodies dealing with EMC 6. Glossary of terms and definitions 7. Abbreviations 8. References Appendix A. Disturbance compatibility levels in figures A-1. Electromagnetic compatibility levels for low-, medium- and high-voltage public distribution networks A-2. Electromagnetic compatibility levels for indoor industrial plants

13. REP-00149, 2000, Understanding power quality problems - Voltage sags and interruptions: 4, Voltage sags - Characterization, Book Chapter 4 of the book "Understanding power quality problems - Voltage sags and interruptions" (IEEE Press, ISBN 0-7803-4713-7) Voltage sag magnitude Voltage sag duration Three-phase unbalance Phase-angle jumps Magnitude and phase-angle jumps for three-phase unbalanced sags Other characteristics of voltage sags Load influence on voltage sags Sags due to starting of induction motors

14. REP-00150, 2000, Understanding power quality problems - Voltage sags and interruptions: 5. Voltage sags - Equipment behavior, Book Chapter 5 of the book "Understanding power quality problems - Voltage sags and interruptions" (IEEE Press, ISBN 0-7803-4713-7) Computers and consumer electronics Adjustable-speed AC drives Adjustable-speed DC drives Other sensitive loads

15. REP-00151, 2000, Understanding power quality problems - Voltage sags and interruptions: 6. Voltage sags - Stochastic assessment, Book Chapter 6 of the book "Understanding power quality problems - Voltage sags and interruptions" (IEEE Press, ISBN 0-7803-4713-7) Compatibility between equipment and supply Presentation of results: voltage sag coordination chart Power quality monitoring The method of fault positions The method of critical distances

16. REP-00155, 2003, Analysis of the neutral conductor current in a three phase supplied network with non-linear single phase loads, Application note This paper describes what factors (i.e. load and supply) have an important effect on the neutral conductor current. It is shown that an asymmetry up to 10° or an unbalance of 10% in the power supply has only a minor effect on the rms-value of the neutral conductor current. An unbalance in load conditions increases the neutral current. Harmonics in the power supply voltage highly affect the rms-value of the neutral conductor current.

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