Basics of Power System Control and Protection

NSF/ECEDHA Education WorkshopGeorgia Tech GLC, Atlanta, Georgia, July 9-12, 2011

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Basics of Power System Control and Protection

A. P. Sakis MeliopoulosGeorgia Power Distinguished Professor

School of Electrical & Computer EngineeringGeorgia Institute of Technology


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School of Electrical and Computer Engineering

Associate DirectorGraduate Affairs

Associate DirectorGraduate Affairs

Chairman (interim)Dr. Douglas B. Williams

Chairman (interim)Dr. Douglas B. Williams

Associate DirectorUndergraduate Affairs

Associate DirectorUndergraduate Affairs

Associate DirectorAssociate Director

Associate DirectorAssociate Director

Computer EngineeringComputer Engineering

Digital Signal ProcessingDigital Signal Processing

Electric PowerElectric Power

ElectromagneticsElectromagnetics

Electronic Designand Applications

Electronic Designand Applications

MicroelectronicsMicroelectronics

Modern OpticsModern Optics

Systems and ControlsSystems and Controls

TelecommunicationsTelecommunications

BioengineeringBioengineering


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Undergraduate Curriculum

ECE3070ECE3070 Electromechanical Energy Conversion

ECE4320ECE4320 Power System Analysis

ECE4321ECE4321 Power System Engineering

ECE4330ECE4330 Power Electronics

ECE4325ECE4325 Electric Power Quality


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Graduate Courses in Power Systems

ECE6320ECE6320 Control and Operation of Power Systems

ECE6321ECE6321 Power System Stability

ECE6322ECE6322 Power System Planning

ECE6323ECE6323 Power System Relaying

ECE8843ECE8843Topics in Electric PowerComputational Intelligence in Power Systems


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Graduate Courses in Power Electronics

ECE6330ECE6330 Power Electronic Devices & Subsystems

ECE6331ECE6331 Power Electronic Circuits

ECE6335ECE6335 Electric Machinery Analysis and Design

ECE6336ECE6336 Dynamics & Control of Electric Machine Drives


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Continuing EducationContinuing EducationContinuing EducationContinuing EducationPower Systems Certificate ProgramPower Systems Certificate ProgramPower Systems Certificate ProgramPower Systems Certificate Program

- All Courses are Coordinated by the Department of

Professional Education

- All Courses are Offered Annually

- Academic Administrator: A. P. MeliopoulosA. P. MeliopoulosA. P. MeliopoulosA. P. Meliopoulos

Core Courses

•Power System Relaying: Theory and Application

•Modern Energy Management Systems

•Integrated Grounding System Design and Testing

•Grounding, Harmonics, & Electromagnetic Influence Design Practices

•Power Distribution System Grounding and Transients

•Power Electronic Devices, Circuits, and Systems

Elective Courses/Conferences

•Fault and Disturbance Analysis Conference

•Georgia Tech Protective Relaying Conference

Core Courses

•Power System Relaying: Theory and Application

•Modern Energy Management Systems

•Integrated Grounding System Design and Testing

•Grounding, Harmonics, & Electromagnetic Influence Design Practices

•Power Distribution System Grounding and Transients

•Power Electronic Devices, Circuits, and Systems

Elective Courses/Conferences

•Fault and Disturbance Analysis Conference

•Georgia Tech Protective Relaying Conference


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Real Time ModelState Estimation

ApplicationsLoad ForecastingOptimization (ED, OPF)VAR ControlAvailable Transfer capabilitySecurity AssessmentCongestion managementDynamic Line RatingTransient StabilityEM Transients, etc.Visualizations

Markets: Day Ahead, Power Balance,Spot Pricing, Transmission Pricing (FTR, FGR), Ancillary Services

Present State of the Art: C&O and P&C Present State of the Art: C&O and P&C Present State of the Art: C&O and P&C Present State of the Art: C&O and P&C

Control & OperationControl & OperationControl & OperationControl & Operation Protection & ControlProtection & ControlProtection & ControlProtection & Control

The Infrastructure for Both Functions is Based on Similar Technologies: Thus the Opportunity to Merge, Cut Costs, Improve Reliability Integration of New Technologies

Component Protectiongenerators, transformers, lines, motors, capacitors, reactors

System ProtectionSpecial Protection Schemes, Load Shedding, Out of Step Protection, etc.

CommunicationsSubstation Automation, Enterprize, InterControl Center

Model Based Control and Operation


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Power Systems Operation

Main Objectives

REGULATIONFrequencyVoltageNet InterchangePollutants

SECURITY

ECONOMICSNet InterchangePollutantsPower TransactionsIPPsEnergy Balance MarketAncillary Services

Tools

DATA AQUISITION SYSTEMSUPERVISORY CONTROLSTATE ESTIMATIONANALYSISOPTIMIZATIONCONTROL

Restructuring

POWER MARKET (SMD)TRANSMISSION TARRIFS (FTR,FGR)CONGESTION MANAGEMENTERO (Electric Reliability Organization)


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Component (Zone) Protection

• Generators• Transformers• Buses• Transmission Lines• Motors• Capacitor Banks• Reactors, etc.

R

12kV

FDRZone

Radial

BusLine

230 kV20 kV

G+GSU Backup

Xfmr


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System Protection

Load Shedding – Frequency / Voltage

Out of Step (Transient Stability)

Transient Voltage Collapse

Special Protection Schemes

G1

2

2x47.4 mile 115 kV Transmission LineG

1 2

Reactance Grounded Gen

800 MVA-15 kV

X1=15.5%,X2=18%,X0=9%

Reactance Grounded Gen

800 MVA-15 kV

X1=15.5%,X2=18%,X0=9%

Generator Angle52 Degrees Generator Angle

-49 Degrees

BUS10

BUS-MID

SOURCE-A

BUS20

BUS30

Va = 63.01 kV

Va = 42.02 kV

Va = 8.400 kV

Va = 61.99 kV

Va = 8.238 kV

Illustration of Voltage Collapse Near the Center of a Stable System SwingVoltage Transitions Are Slow – Undervoltage Protection Should not Operate

Illustration of Two Power System Swings: (a)Stable – Out of Step Relay Should not Operate(b)Unstable – Out of Step Relay Should Operate

Special Protection Schemes are Protective Relaying Functions Concerned with the Protection Against Special System Conditions that May Lead to Catastrophic Results.These System Conditions are Determined with Extensive Studies of Specific System Behavior. Using this Information a SPS is designed that monitors the System and When the Special System Conditions Occur (Recognition Triggers) the System Operates (Automatically or with Operator Review and Action)

A System Disturbance May Create Generation-Load Imbalance Leading to Sustained Frequency Decline. This Condition, if not Corrected, May Lead to Equipment Damage. The Condition Can be Temporarily Corrected by Load Shedding Until Additional Generation can be Dispatched.Similarly, a Disturbance May Create Sustained Voltage Problems. These problems Can be Also Corrected by Load Shedding


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Control & Operation


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Modern Energy Management System Functional Diagram

ENERGY/ECONOMYFUNCTIONS SUBSYSTEM

Load ForecastUnit Commitment

EconomicDispatch

DATA AQUISITION ANDPROCESSING SUBSYSTEM

EconomicInterchangeEvaluation

AutomaticGeneration

Control

OptimalPower Flow

SecurityDispatch

EnvironmentalDispatch

SECURITY MONITORINGAND CONTROL SUBSYSTEM

EmergencyState

EmergencyControls

VARDispatch

SecurityMonitoring

NormalState

ContingencyAnalysis

InsecureState

PreventiveControls

ExtremisState

RestorativeControls

ExternalEquivalents

ParameterEstimation

NetworkTopology

StateEstimation

Displays

SCADAMeasurements

GPS SynchronizedMeasurements

Load Forecast

Power Bids

AncillaryServices

PowerBalanceMarket

CongestionManagement

TransmissionValuation


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OVERVIEW OF ENERGY MANAGEMENT SYSTEMSData Acquisition and Processing Subsystem

RTUCommunicationLink with ControlCenter

G2G1

MW Flow MeasurementMVAR Flow MeasurementkV MeasurementDisconnect Switch StatusBreaker Status

RTU

Contact InputsAnalog Inputs

Contact OutputsAnalog Outputs

MasterStation

Data

Commands

New Technology

GPS SynchronizedMeasurements(Phasors)


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Network Configurator Example

G1 G2

AutoBank500kV/230kV AutoBank

500kV/230kV

SG1 SG2

Breaker OrientedModel

Bus OrientedModel


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State Estimator

Interconnection

G1

MW Flow MeasurementMVAR Flow Measurement

Transformer Tap Measurement

T1

G2

T2

T1

Interconnection

L1

L2

L3

4

3

2

1

5

6

kV Measurement

• MEASUREMENTS:

• STATE:

• FORMULATION:

• SOLUTION:

Traditional State Estimation

Centralized Procedure

ObservabilityBad Data Detection/ID/RejectionParameter Estimation


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Technological Developments


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Relays

P

Q

I

V

CircuitBreaker

CT CCVT

CircuitBreaker

IED-Relay

Comm Link

CT CCVT

The OLD and the NEW


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Indicator

Control

Control Center

CommunicationsTerminal

EncoderDecoder

UserInterface

RTU IED DisturbanceRecorders

Relays

GPS

LocalComputer

CommunicationsTerminal

To Data Base Remote Access

SCADA

SCADA circa 1923

SCADA circa 2003

SCADA Evolution

Communication Standards

Independent of Protection


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Project BackgroundProject BackgroundProject BackgroundProject Background: Substation Architectures: SmartGrid: Substation Architectures: SmartGrid: Substation Architectures: SmartGrid: Substation Architectures: SmartGrid

Protection, Control, Communications

Physical System

GE Hardfiber System

Industry Direction: Single Data Acquisition System for Protection, Control, and Operations


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Important New TechnologyGPS-Synchronization

History of GPS-Synchronized Measurements


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History of GPS- Synchronized Measurements

The Antikythera Mechanism87 BC

GPS Satellite SystemInitiated 1989, Completed 1994


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Important Milestones

1970: First Computer Relay (PRODAR, Westinghouse, Gilcrest, Rockefeller, Udren)

1984: First Commercial µProcessor Based Relay (SEL)

1989: GPS Signal Becomes Commercially Available

1990-91: Phasor Measurement System (Arun Phadke)

1992: Phasor Measurement Unit (PMU) (Jay Murphy, Macrodyne)


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Arun Phadke’s PMSVintage 1990-92several units were sold to AEP, NYPA, others

Block Diagram Published by Arun PhadkeBlock Diagram Published by Arun Phadke

Time Accuracy Was Never Measured or Reported. Multiplexing and Design Suggest Very High Timing Er rorEstimated Time Precision: 100 us, 2 degrees at 60 H z

Time Accuracy Was Never Measured or Reported. Multiplexing and Design Suggest Very High Timing Er rorEstimated Time Precision: 100 us, 2 degrees at 60 H z

CHARACTERISTICS

• Analog Filter with Cutoff Frequency of 360Hz

• Sample & Hold A/D Technology with Analog Multiplexing

• 12 bit S&H A/D 720 s/s

Vintage 1990-91

Several UnitsWere Sold toAEP, NYPA,

others

Arun Phadke’s Phasor Measurement System


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Macrodyne 1620 PMU

A/D Converter(Σ∆ Modulation)

Input Protection &Isolation Section

OpticalIsolation

µP Mem

ory

PLL

Digitized Data2880 s/s

A/D Converter(Σ∆ Modulation)

Input Protection &Isolation Section

OpticalIsolation

Sampling Clock

GPSReceiver

Digitized Data2880 s/s

1PPS IRIGB

GPSAntenna

DataConcentrator(PC)

Display&

Keyboard

RS232

MasterWorkstation

OpticalIsolation

OpticalIsolation

AnalogInputsV : 300VI : 2V

Released to Market January 1992

CHARACTERISTICS

• Individually GPS Sync’d Channels

• Common Mode Rejection Filter with Optical Isolation

• 16 bit A/D Σ∆ Modulation

Time Accuracy 1 µs0.02 Degrees at 60 Hz

Time Accuracy 1 µs0.02 Degrees at 60 Hz

Jay Murphy (Macrodyne) Was First to IntroduceTerm PMU: Phasor Measurement Unit


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Distributed Dynamic State Estimation ImplementationDistributed Dynamic State Estimation ImplementationDistributed Dynamic State Estimation ImplementationDistributed Dynamic State Estimation ImplementationPMU Technology Enables Distributed SEPMU Technology Enables Distributed SEPMU Technology Enables Distributed SEPMU Technology Enables Distributed SE

Phase Conductor

Pot

entia

lT

rans

form

er

CurrentTransformer

PMUVendor A

Burden

Inst

rum

enta

tion

Cab

les

v(t)

v1(t) v2(t)

Burdeni2(t)i1(t)

i(t)

Attenuator

Attenuator Anti-AliasingFilters

RelayVendor C

PMUVendor C

Measurement Layer

Super-Calibrator

Dat

aP

roce

ssin

g

IED Vendor D

LAN

LAN

FireWall

Enc

odin

g/D

ecod

ing

Cry

ptog

raph

y

Data/Measurements from all PMUs, Relays, IEDs, Meters, FDRs, etc are collected via a Local Area Network in a data concentrator.

The data is used in a dynamic state estimator which provides the validated and high fidelity dynamic model of the system.

Bad data detection and rejection is achieved because of high level of redundant measurements at this level.

Physical Arrangement

Data Flow


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Numerical Results Numerical Results Numerical Results Numerical Results –––– BBBB----G PlantG PlantG PlantG Plant


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The dynamic state estimator is utilized to predict the transient stability or instability of a generator. The dynamic state of the system provides the center of oscillations of the generator swing. From this information the potential energy of the generator is computed as a generalization of the basic energy function method.

The total energy of the generator can also be trivially computed once the potential energy has been computed. The total energy is compared to the potential energy of the generator – if the total energy is higher than the peak (barrier) value of the potential energy this indicates that the generator will lose its synchronism (transient instability).

It is important to note that this approach is predictive, i.e. it identifies a transient instability before it occurs.

The figures provide visualizations of generator oscillations and the trajectory of the total energy superimposed on the system potential energy.

Transient Stability Monitoring


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Energy Management SystemsHierarchy of Scheduling Functions

Level 1: Load Forecasting Unit Commitment Emissions ControlEconomy Purchases

Level 2: Economic Dispatch Environmental DispatchEconomic Interchange Evaluation Optimal Power Flow Transfer CapabilityDay-Ahead SchedulingSpot Market Scheduling

Level 3: Automatic Generation Control- Frequency Control- Interchange Control- Transactions Control- Inadvertent Power Flow Control


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Generating Unit Control Schemes Schematic Representation

PrimeMover

G

Exciter

Σ

Vg Pg f

PSSD(s)

GovernorG(s)

L(s)

Σ

Vref

Pg

f

Pg

f

K(s) Σ

Σ PschedBiasBf

Σ

fsched

f

-

+

+

+

+-

+

-++

-

TieLine

TramsmissionSystem

and Load


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Net Interchange Control

Area Control Error (ACE)

PACE =

fBPACE ∆+∆= int

ACEaP igi =∆

GArea 1

G

GArea 3

G G

G

Area 2

G

GArea 4

G

Vi e jδi


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Economic Scheduling Functions Hierarchical Structure

Resource Scheduling(weeks)

Unit Commitment(hours/Days)

Economic Dispatch(minutes)

AutomaticGeneration Control

(seconds)

SecurityDispatch

Mid Term Load ForecastUnits out for maintenanceFuel ManagementWeekly hydro energy usage

Short Term Load ForecastList of committed unitsHourly hydro energy usageInterchange schedule

Economic Base PointsParticipation Factors

Pdesi , i =1,2,...,n

A

B

C

D


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Economic Dispatch

Interconnection

G1



T1

G2

T2

T1

Interconnection

L1

L2

L3

4

3

2

1

5

6

kV Measurement

• MEASUREMENTS

• COST

• FORMULATION

• SOLUTION


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Optimal Power Flow

Interconnection

G1



T1

G2

T2

T1

Interconnection

L1

L2

L3

4

3

2

1

5

6

kV Measurement

• MEASUREMENTS

• STATE

• CONTROLS

• FORMULATION

• SOLUTION


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SYSTEM SECURITY(Congestion Management)Power System Operating States

NORMAL and SECURESystem Optimization

Transition Due to Disturbances

Transition Due to Control Action

Emergency ControlsEmergency

Controls

CorrectiveControls

RestorativeControls

RestorativeControls

Preventive Controls

D,O

D,O

NORMAL butVULNERABLE/INSECUREOptimization/Security

D,O

RESTORATIVESystem Security

D,O

EXTREMISSystem Security

D,O

EMERGENCYSystem Security


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Energy Management SystemsHierarchical Structure

System PowerProduction and

Control (SPPC)

OperationsCoordination

Office (OCO)

RegionalDispatchCenter(RDC)

Substation Power Plant

Power PlantControls

Psched

fsched

ACEVsched

UCE

Vexc


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New Challenges: Wind/PV Farm CharacteristicsTypes 1 and 2 are Not Used for Large Projects

Types 3 and 4 Limit Fault Currents to About 120% of Nominal Current

Proposed Requirements – NERC PRC-024, >20 MVA or >75 MVA Total

Proposed Requirements – NERC PRC-024, >20 MVA or >75 MVA Total


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Renewables and UncertaintySolar is Available During High Price/Cost Hours

Small Storage can provide huge add-on value to solar projects

Better capacity factor than other renewables (70 to 80%)

Wind Availability is Highly Volatile and Patterns May be Opposite to Grid Needs (i.e. CA)

Large Storage Schemes are needed to coordinate economic usage of wind energy and to provide add-on value

Very small capacity factor (10 to 25%)

Large Wind Swings


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Control and Operation of Power Systems is Driven by

(a) Legislative action(b) Economics(c) Technical constraints

The envelop is always moving because of technological advancements

Energy Management Systems: Evolution

ERO Focus: Operational Reliability


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History of Utility Regulatory Legislation

Federal Power Commission

• PUHCA – 1935 (Public Utility Holding Company Act)

Federal Energy Regulatory Commission (1977)

• PURPA – 1978 (Public Utility Regulatory Policies Act)

• Clean Air Act – 1990

• Energy Policy Act – 1992

• Orders 888 & 889 – 1996 (� OASIS )

• CECA – 1998 (Comprehensive Electricity Competition Act)

• Order 2000

• SMD – Standard Market Design

• US Energy Policy Act, 2005 (provides authority to enforce reliability)


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dP g/dP

G enerato r A nim ation - U n it Capab ili tyU nit Nam e

Q g

P g

Sens itiv ities

0 1 3 42

dQ g/dP0 1 3 42

dV g/dP0 1 3 42

RotorHeating

LowVoltage

Visualization & AnimationUniversity of Illinois/Georgia Tech (PSERC Project)

Large Scale SystemsLarge Scale SystemsPerformance Performance -- Model HierarchyModel Hierarchy


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Energy Management SystemsInformation Systems and Standards

OASIS Open Access Same-Time Information System

UCA Utility Communication Architecture

ICCP Inter-Control Center Communications Protocol

CCAPI Control Center Application Program Interface

CIM Common Information Model

IEC61850 Evolution of the UCA

C37.118 Synchrophasor Data


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Active Future Distribution Systems (with distributed energy resources – solar, wind, PHEVs, fuel cells,…).

Smart Grid technologies : Distributed Monitoring, Control, Protection and Operations system. Target Speeds 10 times per second

Functions : (a) Optimal operation of the distribution system under normal operating conditions, (b) Emergency management in cases of faults and assist the power grid when needed, (c) Assist Voltage recovery, (d) Assist cold load pickup, (e) Balance Feeder, (f) etc., etc.


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Evolution, Naxos Island, GreeceJune 25, 2011

Basics of Power System Control and Protection

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