Rothstein Associates Inc.

POWER SYSTEMS IN EMERGENCIES:
FROM CONTINGENCY PLANNING TO CRISIS MANAGEMENT
by U. G. Knight

“As modern society has become increasingly reliant on electricity, disturbances to the power
supply system have become a worldwide industry concern. The range and impact of
disturbances are addressed in this comprehensive account of the planning, operation and
control of power systems during emergencies.

“The impact of a full range of power system emergency situations from adverse weather
conditions and natural disasters to equipment failures, human errors and industrial action.
Detailed coverage of the procedures, organization, training and equipment provided by
utilities in order to contain the incidence and impact of disturbances, both sudden and
predicted.
Survey of the measures adopted to restore electricity supply from various levels of failure.
The development of abnormal operating conditions: descriptions of actual power system
failures and their impacts.

- Discussion of the costs and benefits associated with emergency control.
- Emergency control in the future - the impact of industry restructuring and
deregulation
and the new challenges facing utilities and their staff.
- Offering a clear and concise treatment of the cause, effect and prevention of
power
system emergencies, this timely book will appeal to utility managers, power engineers,
consultants and practitioners involved in, and reliant upon, the electricity supply industry.

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FROM THE INTRODUCTION

“REVIEW OF CONTENTS

“It is surprising that as of the later 1990s, no comprehensive account of the subject of
emergency control of power systems has appeared in book form. This is in spite of its
importance in the planning and operation of power systems, and hence to the integrity of
supply to consumers. The purpose of this book is to provide such a review. It is hoped that it
will be valuable not only to engineers with direct responsibilities for emergency control in
power system design and operation, but also to others associated with the power industry,
for instance system planners and operators, consultants, plant engineers, station staff, R&D
staff, manufacturers, even commercial and financial interests.

“Redundancy will be built into the system structure, and sometimes the individual
components, of power systems, but there cannot be any guarantee that problems will remain
within the levels of contingency allowed in the design margins, that is, that the redundancies
will be sufficient to maintain supplies. If worse problems should occur, any degradation in the
quality of the electricity supply, whether of continuity, voltage, frequency or waveform, should
be of such short duration or small magnitude as to be acceptable to all classes of consumer,
and to the supply industry itself. The body of theory, practice and experience assembled in
the pursuit of this objective has been termed `emergency control'. In short, emergency control
is the assembly of measures provided to ensure continuing stable operation, and then
recovery, towards meeting the normal demand should abnormal system conditions develop.
The questions and requirements posed by this statement will be taken up in the text, and will
include:
- What is system failure and what forms can it take? What is meant by `a
disturbance'?
- The different forms of disturbance, e.g. sudden as a result of environmental
conditions, or
foreseen as a result of shortage of resources; how do these develop?
- What severity of disturbance should be covered by normal protection and control,
leaving
more severe disturbances to be handled by emergency control facilities?
- The measures that can be taken in planning and operation to minimize the impact
of
disturbance.
- The restoration of normal conditions following a disturbance.
- The training of staff to handle disturbed conditions.
- A review of some of the major disturbances that have occurred worldwide;
environmental
factors in disturbances.
- The costs and benefits of emergency control.
- Emergency control in the future.

“Although the basic measures will be common to most systems, the detailed design and
application will be tailored to the characteristics of the individual systems. These
characteristics will change as systems get larger and become more interconnected, new
types of primary plant are introduced, the characteristics of the primary plant change, and
protection and control systems evolve. The emergency control measures should keep pace
with the net effect of all these changes. Checking that this is happening requires experienced
engineers with a critical 'what-if ...?', even skeptical approach, who will regularly review the
contingencies studied, the system conditions assumed, and the adequacy of the models
used, this to be done for the present, near and longer term futures. Experience from other
countries and utilities will be valuable.

- - - - - -

“The chapter by chapter contents of the book are as follows:

“Chapter 2 - Disturbances in Power Systems and their Effects

“This chapter reviews the disturbances which may confront a power system and the potential
impact of these on its viable operation. Disturbances are classified as `sudden', that is there
is no warning of their onset, or 'predictable'/'foreseen', and possible causes for each are
outlined. The possible forms of system failure are then reviewed - plant loading and other
operating parameters outside limits, instabilities, system separations - and an outline of
analytical techniques applicable to their evaluation described. The chapter concludes with
views on trends in the development of analytical techniques.

“Chapter 3 - Some General Aspects of Emergency Control

“Definitions, concepts and standard terminology used in the literature on
emergency
control are introduced in this chapter. The impact of disturbances is pursued further,
including
the preferred corrective actions, the possible consequences if the actions are insufficient,
and the ways in which disturbances can then typically develop to, in extreme cases, a
complete loss of supply. Following a brief comment on the effect of system structure on the
form of emergency control, design criteria for emergency control facilities are proposed.

“Chapter 4 - The Power System and its Operational and Control Infrastructure

“This chapter provides a system and operational background for the remainder of the book,
covering the following main issues:
- structure, function and alternatives for main transmission, including direct current
transmission and FACTS devices;
- standards of security and quality of supply in planning and operation;
- timescales and tasks in system operation and control;
- SCADA facilities - functions, structure, performance criteria, data and human -
computer
interface;
- energy management systems;
- communications, telemetry and telecommand; and
- distributed generation.

“Chapter 5 - Measures in the Planning and Operational Timescales to Minimize the Impact of
Sudden Disturbances and of Foreseen Disturbances

“One of the core topics of emergency control will be reviewed in this chapter, namely what
measures should be taken in the management, planning and operation of power systems to
minimize the effects of disturbances on their viable operation. The objectives of the
measures should be to reduce both the frequency of such disturbances and their harmful
effects if they do occur. The chapter opens with an assessment of factors affecting the onset,
severity and propagation of a disturbance. Measures to minimize the risk are then
discussed,
for both the planning and operational timescales.

“The measures surveyed include:
- generation margins, demand adjustment, under frequency relays and load
shedding,
operational memoranda and procedures, on-line security assessment, special protection
schemes and co-ordinated defense plans used in several countries;
- general measures such as rapid fault clearance; and
- handling predicted disturbances, including natural phenomena, incipient plant
breakdown, industrial action outside and within the supply industry.

“Chapter 6 - The Natural Environment, Some Disturbances Reviewed

“Nature imposes an environment on power systems which man can influence in the long term
- usually it seems for the worse - but hardly at all in the short term (some of the `killer smogs'
that occurred in the UK in the early 1960s and continue in other parts of the world are
perhaps exceptions to this generalization). Also, global warming seems to be happening at
an increasing rate, with effects perceived in decades rather than centuries as in the past,
and
in part blamed on human activities. Extreme weather and other environmental conditions will
determine many of the plant and system criteria. Hence, it is important to have an
appreciation of the weather conditions which may occur. The first part of this chapter reviews
these, mainly qualitatively, whilst the second part gives brief descriptions of disturbances
from around the world. Datewise, the disturbances range from the mid-1970s to the end of
1999. Some have involved virtually the total loss of supply to whole countries, and others
have
been `near misses'. Where available, the lessons learnt from the disturbances have been
included.

“Chapter 7 - Restoration

“The objective of power system restoration is to bring the system to a point at which as much
demand as possible, within the capacity of the generation and transmission remaining after
the disturbance, is supplied at acceptable frequency, voltage and security levels. In practice,
restoration will be a combination of operator decisions and automatic control actions.
Following an appreciation of the factors which define the range and severity of a disturbance,
the general issues which must be settled before a restoration strategy can be built up are
listed - priorities in restoration, etc. Actions for restoration from a localised failure are
described, followed by an extended review of the `black start' situation. Aids to the
restoration process are listed. The chapter concludes with descriptions of some of the
problems which hinder restoration.

“Chapter 8 - Training and Simulation in Emergency Control

“The human component in decision making is more important in real time system operation,
particularly during disturbed conditions, than in most areas of system engineering, and it is
appropriate to discuss the training of system operators in this book. The general approach to
training adopted in the supply industry is outlined followed by descriptions of need, content
and forms of training for system operators.

“Training usually requires access to an operational or mock up control engineer's desk
(increasingly called workstation), and the ways in which this can be provided are outlined -
for
instance, use of a standby desk (sometimes even a standby control room) and supporting
computer systems when not required for operation, or a stand-alone simulator and
workstation. The chapter includes short descriptions of training simulators installed by the
National Grid Company (England and Wales), Electricite de France (France), Svenska
Kraftnet (Sweden) and EPRI (USA), and concludes with statistics on the use of dispatch
training simulators.

Chapter 9 - Plant Characteristics and Control Facilities for Emergency Control and Benefit to
be Obtained

“I had originally intended to provide a simple comparison of the cost of emergency control
facilities against an estimate of the benefits to be achieved by their installation. Several
factors noted in the chapter precluded this, and instead the first part of this chapter reviews
total facilities and characteristics for emergency control which should be considered by a
utility, with emphasis on functions and relationships to normal control, whilst the second part
discusses benefits in qualitative and quantitative terms.

“The characteristics of plant, system and demand of particular importance in emergency
control are considered first, followed by views on the system control facilities specifically
provided to handle emergencies. Qualitative and quantitative benefits of emergency control
are discussed, and the chapter ends with a brief comment on the question `Is emergency
control worthwhile?'.

“Chapter 10 - Systems and Emergency Control in the Future

“This is a wide ranging chapter which attempts a forecast of the role of
emergency
control in the future. This is considered from two aspects - organizational changes and
facilities - noting that restructuring and unbundling have occurred in numerous countries. The
regulatory aspects are illustrated by reference to several utilities, the current and future
regulatory background being described. Short descriptions of some of the relevant
international organizations are included - the European Union, UCPTE and CIGRE. The
regulatory framework of several countries is also summarized.

“The second part of this chapter describes some of the expected trends in organizations,
systems, manpower, supply standards and plant. The major part is on control plant
developments covering static var compensators, series compensators, unified power flow
controllers, new type storage systems, FACTS devices in general, etc.

“In view of its growing importance worldwide, the possible impacts of privatization and
restructuring within the industry are discussed in this chapter.

“Appendix 1 - Some Major Interconnected Systems Around the World: Existing and Possible
Development

“Perhaps more than at any other time, emergencies demonstrate the values of
interconnection in providing mutual support between utilities. Hence, this appendix outlines
some of the intranational and international interconnections that have been formed, some
almost piecemeal and others through development policies.

“Appendix 2 - Glossary of Useful Terms

“Power system engineers have assembled their own concise vocabulary to describe
conditions and events within a power system, and this appendix provides a comprehensive
glossary of terms found in this book, and the literature in general.

Appendix 3 - Modelling

“The power system analysis techniques used in planning and operation for normal conditions
are applicable in emergency control, although there may be increased emphasis on
obtaining rapid solutions. This has meant that in the past, approximations have been used to
achieve these. The continuing improvement in the performance of computers has now
decreased the importance of these. As many descriptions of models and analytical
formulations have been published, particular examples have been summarized. Mention is
also made of the `slick' handling of data and the incorporation of results into operational
decisions.

1.2 GENERAL APPROACH OF THE BOOK

“The approach is practical, describing the criteria and means adopted by utilities to prevent
and control emergency conditions. Mathematical details are kept to a minimum and are
mainly concentrated in Appendix 3.”

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CONTENTS

PREFACE

1 INTRODUCTION AND CONTENTS

1.1 Review of Contents
1.2 General Approach of the Book

2 DISTURBANCES IN POWER SYSTEMS AND THEIR EFFECTS
2.1 Sudden Disturbance
2.1.1 Weather
2.1.2 Environment
2.1.3 Balance between Demand and Generation
2.1.4 Plant Failure
2.1.5 Human Error
2.2 Predictable Disturbances
2.2.1 Shortage of Plant Capacity
2.2.2 Shortage of Fuel
2.2.3 Shortage of `Ancillary' Supplies
2.2.4 Shortage of Operating Staff
2.2.5 Shortage of Control Staff
2.3 Forms of System Failure
2.3.1 Thermal Overloads
2.3.2 Switchgear Ratings, Excessive System Fault Levels
2.3.3 Voltage Outside Limits
2.3.4 Frequency Outside Limits
2.3.5 Steady State, Transient and Dynamic Stability
2.3.6 Voltage Instability
2.4 Analysis Techniques
2.4.1 Steady State Flows and Voltages
2.4.2 Fault Levels
2.4.3 Transient Stability
2.4.4 Dynamic Stability
2.4.5 Medium and Long-term Stability
2.5 Trends in the Development of Analytical Techniques References
Further Reading

3 SOME GENERAL ASPECTS OF EMERGENCY CONTROL
3.1 Definitions and Concepts used in Emergency Control
3.1.1 Definitions
3.1.2 System States
3.1.3 Objectives
3.1.4 System States, Contingencies and Types of Control
3.2 Some Standard Terminology
3.3 The Effects of Various Types of Fault or Disturbance on System Performance
3.3.1 Sudden Deficit of Generation or Equivalent
3.3.2 Sudden Deficit of Demand or Equivalent
3.3.3 Sudden Loss of Transmission (Not Resulting in an
Immediate System Split)
3.3.4 Sudden Loss of Transmission (Resulting in a System Split)
3.4 Typical Pattern of the Development of a Sudden Disturbance
3.5 Conceptual Forms of Emergency Control
3.6 Effect of System Structure on the Need for and Implementation of Emergency
Control
3.6.1 Effect of System Structure on the Form of Emergency Control
3.7 Design Criteria for Emergency Control Facilities References

4 THE POWER SYSTEM AND ITS OPERATIONAL AND CONTROL
INFRASTRUCTURE
4.1 Structure
4.1.1 A Theory on the Evolution of Network Voltages
4.2 The Functions of Interconnection
4.2.1 Exchanges Between Neighbours
4.3 The Alternatives for Main Transmission
4.3.1 The Roles of Direct Current Interconnection and Transmission
4.4 Security and Quality of Supply in Planning and Operation
4.4.1 Standards of Security in Planning
4.4.2 Standards of Security in Operation
4.4.3 Standards of Quality
4.5 Timescales in System Operation and Control
4.5.1 Operational Planning
4.5.2 Extended Real-Time Analysis
4.5.3 Real-Time Operation
4.5.4 Facilities
4.5.5 Post-Event Tasks
4.5.6 Operator Training
4.5.7 Models Used in Post-Event Tasks
4.6 SCADA
4.6.1 Questions on Functions and Structure
4.6.2 Questions on Performance Criteria
4.6.3 Information Required at Control Centres
4.6.4 Information Sent Out from Control Centres
4.6.5 The Human-Computer Interface
4.6.6 Availability Requirements for SCADA Systems and their Structure
4.7 Energy Management Systems
4.8 Communications and Telemetry 4.9 Telecommand
4.10 Distributed Generation
4.11 Flexible a.c. Transmission Systems (FACTS)
4.11.1 Factors Preventing Full Thermal Loading of Circuits in an a.c. Network
4.11.2 Some FACTS Devices References
Further Reading

5 MEASURES TO MINIMIZE THE IMPACT OF DISTURBANCES
5.1 Factors in Onset, Severity and Propagation of a Disturbance
5.2 Measures in the Planning Timescale to Minimize the Risk of a Disturbance
5.2.1 The Basic Formulation
5.2.2 Generation Provisions in the System Plan
5.2.3 Measures for Demand Adjustment in the System Plan
5.3 Measures in the Operational Timescale to Minimize the Risk and Impact of a
Disturbance
5.3.1 Under-frequency Load Disconnection
5.3.2 Other Frequency Control Mechanisms
5.3.3 Memoranda and Procedures
5.4 Special Protection Schemes
5.4.1 The Elements of a Special Protection Scheme
5.4.2 The Performance of SPS
5.4.3 Prevention of Overload and Instability
5.4.4 System Application of SPS
5.5 Reduction in the Spread of Disturbances
5.5.1 Rapid Clearance of Faults
5.5.2 Sustainable Conditions Following the Initial Fault Clearance
5.5.3 Restoration of Normal Conditions
5.6 Measures to Minimize the Impact of Predictable Disturbances
5.6.1 Natural Phenomena
5.6.2 Incipient Breakdown of Plant
5.6.3 Labour Problems
5.7 An Approach to Managing Resources
5.8 The Control Centre
5.8.1 SCADA
5.8.2 Main, Standby and Backup SCADA/EMS Systems
5.8.3 Communications
References
Further Reading

6 THE NATURAL ENVIRONMENT -SOME DISTURBANCES REVIEWED
6.1 Introduction
6.2 Useful Sources of Information
6.2.1 Government and Similarly Sponsored Inquiries
6.2.2 Utility Inquiries
6.2.3 Annual Reports
6.2.4 International and National Surveys
6.2.5 The Internet
6.3 Extreme Environmental Conditions
6.3.1 Hurricanes
6.3.2 Tornadoes
6.3.3 Gales
6.3.4 Hail, Snow and Icestorms
6.3.5 Earthquakes and Tsunamis
6.3.6 Vegetation Brushfires
6.3.7 Thunderstorms, Lightning and Overvoltages
6.3.8 Floods
6.3.9 Geomagnetic Storms
6.3.10 Disaster Control
6.4 Noteworthy Disturbances
6.4.1 The Questionnaire
6.4.2 An Example (a Complex Fault on a Simple System)
6.4.3 Tabular Information on Disturbances
6.4.4 Descriptions of Disturbances
6.5 Incidents
6.5.1 UK-August 1981
6.5.2 UK-1986
6.5.3 UK-October 1987
6.5.4 France-1999
6.5.5 Scandinavia-1997
6.5.6 Malaysia-1996
6.5.7 New Zealand-late January-early March 1998
6.5.8 Australia-1977
6.5.9 Australia -1994
6.5.10 USA-July 1986
6.5.11 USA-1989
6.5.12 USA-September 1989
6.5.13 USA-August 1996
6.5.14 Canada-January 1998
6.5.15 Canada and USA-January 1998
6.5.16 USA-January 1998
6.5.17 USA-January 1998
6.5.18 USA-March 1998
6.6 Conclusion
References

7 RESTORATION
7.1 Introduction
7.2 The Range of Disturbed System Conditions
7.3 Some General Issues in Restoration
7.4 Recovery from an Abnormal Operating Situation, Local Islanding or Localized
Loss of
Demand
7.4.1 Checking System Security during the Restoration Process
7.5 The `Black Start' Situation
7.5.1 The Generation Demand Balance
7.5.2 The System Reactive Balance
7.5.3 Status of the Control and Protection Facilities
7.6 Strategies for Restoration of the Whole System
7.6.1 Preparation of the System
7.6.2 Rebuilding the Transmission System
7.7 Aids in the Restoration Process
7.7.1 Operational Planning Studies
7.7.2 Expert Systems
7.7.3 Automatic Systems Switching
7.8 Problems Found in Restoration
7.9 Analysis, Simulation and Modelling in Blackstart
7.9.1 In-depth Analysis
7.9.2 Routine but Complex Analysis
7.9.3 Operation Studies in the Event
7.10 Restoration from a Foreseen Disturbance Further Reading

8 TRAINING AND SIMULATORS FOR EMERGENCY CONTROL
8.1 Introduction
8.2 Training in General
8.3 The Need for Operator Training
8.4 The Content of Training
8.5 Forms of Training
8.5.1 Father-Son Tuition
8.5.2 Group Discussion
8.5.3 Training Courses
8.5.4 Organization of Training Courses
8.5.5 Assistance in Commissioning
8.5.6 Self-tuition
8.6 Training Simulators
8.6.1 Outline Specification for a Training Simulator
8.6.2 Alternative Forms of Training Simulators
8.6.3 Some Commercial Training Simulators
8.6.4 The New Generation of Dispatch Training Simulators
8.7 The Use of Dispatch Training Simulators in Practice
8.8 Conclusion
References
Further Reading

9 PLANT CHARACTERISTICS AND CONTROL FACILITIES FOR EMERGENCY
CONTROL, AND BENEFITS TO BE OBTAINED
9.1 Introduction
9.2 The Characteristics and Facilities Required for Emergency Control
9.2.1 Generating Plant
9.2.2 Transmission Plant
9.2.3 Overhead Lines
9.2.4 Cables
9.3 The System and Demand
9.3.1 Configuration
9.3.2 Demand
9.3.3 Adjustment of Active Power Flow
9.3.4 Adjustment of Reactive Power Infeeds
9.4 System Control Costs for Emergencies
9.5 Indirect Costs
9.6 The Benefits of Emergency Control
9.6.1 Qualitative Aspects
9.7 Quantitative Aspects
9.8 Is Emergency Control Worthwhile?
References
Further Reading

10 SYSTEMS AND EMERGENCY CONTROL IN THE FUTURE
10.1 Introduction
10.2 Changes in Organization
10.3 Restructuring, Unbundling and Emergency Control
10.3.1 Regulatory Aspects
10.4 Facilities for Emergency Control in the Future
10.5 Superconductivity
10.6 Contingency Planning and Crisis Management
References
Additional Reading

APPENDIX 1 SOME MAJOR INTERCONNECTED SYSTEMS AROUND THE
WORLD:
EXISTING AND POSSIBLE DEVELOPMENTS WESTERN EUROPE
England, Wales and Scotland (as at the mid-late 1990s)
Scandinavia
Part Central and Eastern Europe
A Baltic Ring
Central Europe
North America
India
Middle East and North Africa
Peoples' Republic of China
Africa
South America
Central American Power Grid
Information Sources

APPENDIX 2 GLOSSARY OF USEFUL TERMS REFERENCES

APPENDIX 3 SOME USEFUL MATHEMATICAL AND MODELLING TECHNIQUES
IN
POWER SYSTEMS STUDIES
A3.1 Linear Programming
A3.2 Some Special Forms and Extensions of Linear Programming
A3.2.1 Transportation
A3.2.2 Integer Linear Programming
A3.2.3 Quadratic Programming
A3.3 Non-linear Programming
A3.3.1 The Indirect Approach Using Lagrangian and Kuhn-Tucker Multipliers
A3.3.2 The Direct Approach Using Gradient Methods
A3.4 Dynamic Programming
A3.5 Operating Costs
A3.6 Power System Analysis
A3.6.1 Power Flows and Voltages
A3.7 The d.c. Approximation References
Further Reading

Index

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2001, 392 Pages. Order #DR584.
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