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Power Quality Training Courses

Voltage dips and short interruptions

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Module 1 Voltage dips and short interruptions 1 INTRODUCTION In the existing situation in Polish power system, due to a dearth of comprehensive measurements and, in consequence, insufficient knowledge on the quality of supply, the acquisition of measurement data about voltage dips and short supply interruptions will be the task for the nearest future. Currently, these disturbances would be the subject of a contract only in specific cases. 1.1 General aims Two kinds of electromagnetic disturbances are dealt with in this seminar: voltage dips and short supply interruptions. Their sources and effects, as well as possible methods of their mitigation and measuring, are briefly described in the scope, which is sufficient for formulation of contractual provisions. The issues that should be taken into account in concluding a contract between the supplier and consumer of electric power are considered on the basis of the existing standards and regulations.

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. 1st day Contents

Aims

Contents

Aims

Introduction Effects of voltage dips and short interruptions Remedial measures Improvement of equipment immunity Supplying knowledge concerning basics of voltage dips and swell, sources, effects, methods for mitigation 2nd day Contract Examples of selected contracts and national regulations Indices based on the voltage change and energy-related indices Case studies Laboratory Supplying knowledge concerning principles of measuring, standardization, formulating contracts. Use of the obtained knowledge to analysis and solving problems, as well as to practical measurements in laboratory.

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

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2.1

Pathway of learning flow chart Time progression (hours)

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COURSE DETAILED PROGRAM

First day: 60 mins

Participants registration - Akademia Górniczo-Hutnicza, Kraków Pawilon B1, sala 25

5mins

Openning, informations, course introduction, course introduction

55 mins

Section 1: Introduction − Definitions − Description of the disturbance (sources of voltage dips; voltage dip duration, magnitude of a voltage dip; transformer and load connections, short supply interruptions) Modality: Lesson and discussion

60 mins

Effects of voltage dips and short interruptions (IT equipment and control systems; contactors and relays; induction motors; synchronous motors; variable speed drives; high pressure discharge lamps) Modality: Lesson and discussion

15 mins

Coffe break

60 mins

Section 2: Remedial measures (reduction of the number of faults; reduction of the fault clearance time; modification of the supply system configuration; installing voltage stabilizers) Improvement of equipment immunity Modality: Lesson and discussion

Second day: 45 mins

Section 3: Measurement of voltage dips and short interruptions (principles of measurement; reference voltage for measurement purposes; dip duration voltage thresholds marking start and end of the disturbance - fixed reference voltage and sliding reference voltage; distinguishing between voltage dips and short interruptions; reporting measurements results; example of measurement results)

45 mins

Methods of analysis - statistical methods and direct measurements − Standardisation Modality: Lesson and discussion

15 mins

Coffe break

60 mins

Section 4: Contract (duration of measurements; reference voltage value; location and method of connection measuring instrument; technical specifications for measuring instrumentation; threshold values for disturbance detection; techniques of reporting the measurement results; methods for aggregation of measurement results - voltage-level aggregation, phase aggregation, time aggregation, space aggregation) Modality: Lesson and discussion

60 mins

Examples of selected contracts and national regulations − Indices based on the voltage change (Integral of voltage-loss; Voltage-sag severity index; RPM Power Quality index approach) Modality: Lesson and discussion

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15 mins

Coffe break

60 mins

Section 6: Energy-related indices (voltage dip energy; indices based on symmetrical components) − Voltage-dip co-ordination chart − Case studies Modality: Lesson and discussion

60 mins

Laboratory Modality: Lesson and practical training

30 mins

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

GENERAL NOTES − − − −

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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; www.lpqi.org

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lecture notes containing all or part of the lecture slides; 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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identification of the disturbance nature disturbance source identification disturbance assessment by means of measuring evaluation of technical and economic effects of disturbance proposing remedial measures formulation of contract between the supplier and consumer of electric power on the basis of the existing standards and regulations

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

2. PR-00012, Gomez, J, Coordinating overcurrent protection and voltage sag in distributed generation systems, IEEE Power Engineering Review, Feb 2002 The new scenario implies that the time-voltage characteristic of a protective device changes into a zone that modifies previous methodologies and increases the dropout susceptibility of sensitive equipment.

3. PR-00020, Gurney, J, Hughes, B, Li, C, Neilson, B, Xu, W, Virtual PQ troubleshooter, IEEE power & energy magazine, may/june 2003 The authors describe a prototype instrument that locates the sources of power quality disturbances and is geared toward power system troubleshooting and management.

4. PR-00021, Craven, K L, Lawrence, R, Nicholls, M, Flywheel UPS, IEEE Industry Applications, May/June 2003 An economical energy storage device that bridges the gap caused by voltage sags and temporary voltage loss.

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Publication 5. REP-00002, 2004, 1-9 Power Quality Glossary, Application note The glossary of main technical terms used in PQ

6. REP-00004, 2003, 2-3 Persuading consumers to invest in voltage sag, Application Note Investement analysis of voltage dips mitigation methods

7. REP-00022, 2003, 5-3-4 Considerations for choosing different voltage dip mitigation devices, Application Note Sensitive loads. Mitigation devices and their performance This paper compares various systems protecting industrial processes against voltage sags (Flywheel, Static UPS, Dynamic Voltage Restorer, Statcom, Shunt connected Synchronous Motor and a Transformerless Series Injector). The systems are compared with regard to dip immunization capability and several other technical and economic parameters.

8. REP-00028, 2003, 6-2-2 Power quality measurement technology: fit for the future, Application Note Somehow Fluke philosophy of PQ measurement - hints. Subjects: - The main problems - A comparison of the approaches: former vs. future - New opportunities - New tools for the power quality measurement technology of the future

9. REP-00046, 2002, 5-1 Voltage dips - Introduction, Application note Dips causes. Sensitivity; CBEMA, ITEC, ANSI curves.

10. REP-00048, 2003, 5-2-1 Predictive Maintenance - The key to Power Quality, Application note The concept of predictive maintenance. Rhopoint Systems - PQ Index

11. REP-00049, 2002, 5-3-2 Voltage Dip Mitigation, Application note Overview of different voltage stabilizers.

12. REP-00051, 2003, 5-5-1 Voltage Sag in Continuous Processes. Case Study, Application note How to mitigate voltage dips in vulnerable areas of textile factory.

13. REP-00057, 2003, TECHNO-ECONOMIC ANALYSIS OF METHODS TO REDUCE DAMAGE DUE TO VOLTAGE DIPS, Application note This is the text of a Ph D thesis. To determine whether there are cost effective mitigation methods to avoid or limit damage caused by voltage dips, requires detailed information on several aspects, such as an estimation of the number of dips to be expected, an overview of possible solutions and a correct economic decision-making criterion. The current literature describes these aspects in an isolated way, neglecting the interactions between the coupled aspects. This work describes and completes the aspects involved. Furthermore, it combines them in a coherent framework, resulting in an applicable strategy to find the best technoeconomic solution in a concrete situation. The applicability of the introduced methods is demonstrated by case studies of industrial processes in an existing grid. Chapters: 1. Introduction 2. Problem analysis 3. Dip characterization and propagation 4. Estimating dip frequency: area of vulnerability 5. Estimating dip frequency: dip measurements 6. Mitigation methods 7. Cost-benefit analysis of mitigation methods 8. Integration of all aspects 9. Textile fiber extrusion process 10. Summary, conclusions and future research

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14. REP-00072, 2003, Voltage dip immunity test set up for induction motor drives, Application note Variable-speed drives are sensitive to voltage dips. A test set-up for assessing the immunity of standard induction-motor drives to dips in the supply voltage is described. Measurements result in voltage-tolerance curves. Measurements are compared to simulation results.

15. REP-00110, 2003, Voltage sag measurement and characterization. Technical note no. 4., Application note Voltage sag measurement and characterisation - subjects: 1. Introduction 2. Load susceptibility 3. Event reporting 4. Site reporting 5. Site indices 6. Sag surveys

16. 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.

17. REP-00126, 1998, Using voltage sag and interruption indices in distribution planning, Paper A traditional approach to distribution planning calls for the most economical system upgrades, timed to meet projected capacity needs. In a more competitive environment, there is also value in improving the power quality. Power quality impacts, especially in the areas of RMS voltage variations and sustained interruptions, can alter the economic evaluation of investment options for capacity expansion. While it may appear attractive to feed new load from a particular substation, an increased sag rate may result, favoring a different solution. This paper describes a planning process that includes power quality impacts. The process is dependent on service quality indices that measure the performance of the system. Methods for estimating the indices from measurements and simulations are discussed. An example is presented that illustrates how consideration for the cost of RMS variations and sustained interruptions can alter the planning decision.

18. REP-00127, 2002, Power quality indices and objectives. Ongoing activities in CIGRE WG 36-07, Paper This paper gives an overview of the ongoing activities in CIGRE WG36-07: "Power quality indices and objectives". It introduces the considerations supporting the need for power quality indices and objectives in the present context of deregulation of the electricity industry. Experts generally agree on the need for standardized quality indices allowing to monitor and to report power quality in a common format. However, concerning quality objectives the need is more likely for different levels of quality that can match customers expectations and the price they are wilting to pay for electricity. Some practical limitations to voltage quality monitoring are also discussed. The status of the work within the working group is described for harmonics, flicker, unbalance and voltage dips.

19. REP-00130, 2001, Variable speed drives and motors - motor shaft voltages and bearing currents, Application note This user guide provides information to enable the correct selection and installation of low voltage induction motors and Voltage Source PWM inverters with respect to minimising the effects of shaft voltages and potentially damaging bearing currents.

20. REP-00141, 2002, Voltage dip immunity test set-up for induction motor drives, Paper Paper presents test set up to determine immunity of a motor to voltage dip.

21. 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 www.lpqi.org

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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 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

22. REP-00146, 2000, Understanding power quality problems - Voltage sags and interruptions: 1. Overview of power quality and power quality standards, Book Chapter 1 of the book "Understanding power quality problems - Voltage sags and interruptions" (IEEE Press, ISBN 0-7803-4713-7) Interest in power quality Power quality, voltage quality Overview of PQ phenomena PQ and EMC standards

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