role of gps synchronized measurements in power system ... · role of gps synchronized measurements...

1Tele-Seminar, April 30, 2004PSERC

April 30, 2004PSERC Tele-Seminar

April 30, 2004PSERC Tele-Seminar

Role of GPS Synchronized Measurements in Power System Visibility

Role of GPS Synchronized Measurements in Power System Visibility

Sakis MeliopoulosGeorgia Tech

Sakis MeliopoulosGeorgia Tech


Outline

• Power System Visibility (Real Time Model)

• GPS Synchronized Measurement Technology

• Data Validation – Issues

• NYPA’s HMS

• Hybrid State Estimator

• Numerical Experiments


Recommendation 22Evaluate and adopt better real-time tools for operators and reliability coordinators.

Bits & PiecesFrom

US-Canada Power System Outage Task Force

Contributing FactorsInadequate Situational Awareness


Observations

Basic Task in System Operation:Obtain a Reliable and Accurate Real Time Model

Past and Present Practice:SCADA + State Estimator Real Time Model

Today’s Reality:SCADA, IEDs, DFRs, PMUs, Relays Collect an EnormousAmount of Data. Is There a Better Way to Validate andUtilize this Data?


Basic Capabilities

• GPS “Commercial” Accuracy (Time):0.5 MicrosecondsPhase Error 0.01 Degrees at 60 Hz

• GPS “Commercial” Accuracy (Location):7 meters

• New Enhancement:WAAS (Wide Area Augmentation System)Performance Much Better

• Other Enhancements in the Works…


GPS-Synchronized Measurements

• Technology Became Available to Power Systems About 15 years ago

• Specialized Equipment

• Addition of GPS Synchronization in IDEs and Relays

• Cost is Rapidly Reducing (Basic Receiver is $30)

• Technology is Under-Utilized


IED Cordova

IED West Point

IED VolunteerIED Johnsonville Fossil Plant

IED Kanawha River

IED Callaway, Ameren

IED Rockport, AEP

IED Rush Island, Ameren

ECARMAIN

IED Jacksons Ferry, 765 kV

IED Orange, AEP

Planned GPS-Synchronized Measurements for the TVA System


2 2

1

2

239

62

4

1

9067

5

43

24

10

82

24515

840

19

4

2

Courtesy of SELCourtesy of SEL

SEL-421 Deployment Eastern USA


By Virtue of its Timing Accuracy the Technology Can Be Used to Directly Measure the State of the Power System

GPS-Synchronized Measurements


Measurement ErrorsGPS Synchronized Measurements are More Accurate than Sensors but still Imperfect – Errors are PresentSensorless SCADA Have Accuracy Comparable to GPS Synchronized Measurements

System Exhibits “Internal” ErrorsErrors from InstrumentationErrors from ImbalanceErrors from Asymmetry

SolutionData Filtering via Estimation Methods Validation

Important Observations


RS232Ethernet and RS232Communications0.01 Degrees0.01 DegreesPhase Measurement Error at 60 Hz

Digital(built in A/D Converter)

noAnti-Aliasing FiltersopticaltransformerCurrent Input Isolationopticaldifferential amplifierVoltage Input Isolation

yesnoGPS synchronized samplingyesnoSimultaneous SamplingyesyesGPS Time TaggingnoyesAutomatic Calibration

288010240Sampling Rate (samples per second per channel)

16 bits14 bitsA/D Converter Word Length

Sigma-Delta Modulation

Successive Approximation

A/D Converter Technology

Macrodyne1620

Arbiter1133A

Example Specifications


Example Characteristics of a PMU


Errors from Imbalance and Asymmetry


180 660 1140 1620 2100

0.06

0.04

0.02

0.0

Series Admittance

Shunt Admittance

Frequency (Hz)

Asym

met

ry F

acto

rValidity of Power System Symmetry Assumption

1

minmax1 2

1z

zzS

−=

1

minmax2 2

1y

yyS

−=

The Phase Impedances May

Vary by 5% Among Phases


Phase Conductor

PotentialTransformer

CurrentTransformer

PhasorMeasurementUnit

ComputerBurden

InstrumentationCables

v(t)

v1(t) v2(t)

v3(k)

Burdeni2(t)i1(t)

i(t)

Attenuator

Attenuator

Instrumentation Errors


G

1 2

1 2V

V

V

V

A

A/D

V

PT, 66.4kV:115VControl Cable, RG-8

A/D Converter

IC AnimatorVoltage Meter Voltage Meter

SOURCE BUS115 BUS115A

LOAD

PTOUT VCHINPUT VADOUT

BUS115B

Instrumentation ErrorsVoltage Measurement Error During Transients


0.140300 m0.110225 m0.070150 m0.04075 m

Phase ( Vout / Vin )Cable Length (l)

Vinput

VoutputWoundType PT Burden

l

Instrumentation ErrorsInstrumentation Cable Phase Error

PMU PhaseAccuracy is0.01 degrees

PMU PhaseAccuracy is0.01 degrees


Power System SE: Basic Assumptions• Positive Sequence Model• P, Q, V measurement set• Instrumentation Errors Part of Meas Data• Near-Simultaneous Measurements• Single Frequency

Implications:• Balanced Operation• Symmetric Power System• Biased SE• Iterative Algorithm

Traditional State Estimation


NYPA’s Harmonic Measurement System Using GPS Synchronized Measurements (Macrodyne’s PMUs)

I

Global TimeReference

(GPS)

GPSReceiver

MicroprocessorA/D

Phasor data(time stamped)SerialCommunicationPort

Filte

r

To Control Center

Harmonics DataConcentrator

(Located in Atlanta)

PMU Block Diagram

V

GPS Antena

ADD BulletinBoard System

GIC DataConcentrator

Located at NYPP

PMUComputer

PMUComputer

PMUComputerHMS Host System

Massena

Marcy

Niagara

Fraser

Robinson PTS

PTS

Albany

Coopers Corner

1 2

PTS

PTS

PTS

PTS

PTS

MASENA765

MARCY765

NIAGARA ROBINSON

EDIC

MARCY345

NSCOTLAND

VOLNEY

FRASER

COOPERSC

CLAY MARCY-T1MARCY-T2

OAKDALE

GILBOA

FRASER115

ROB115ROB-T1

STOLLE

HINMAN

LOCUST

HARISON

NIAG230

NIAG-T1

NIAG-T2

NR-2 PA-301PA-302

MASNA230BMASNA-T1

MASNA230AMASNA-T2

MOSES230

MMS2

CHTAUG765

LAFAYETTE

HMS Host SystemMassena

Marcy

Niagara

Fraser

Robinson PTS

PTS

Albany

Coopers Corner

1 2

PTS

PTS

PTS

PTS

PTS

MASENA765

MARCY765

NIAGARA ROBINSON

EDIC

MARCY345

NSCOTLAND

VOLNEY

FRASER

COOPERSC

CLAY MARCY-T1MARCY-T2

OAKDALE

GILBOA

FRASER115

ROB115ROB-T1

STOLLE

HINMAN

LOCUST

HARISON

NIAG230

NIAG-T1

NIAG-T2

NR-2 PA-301PA-302

MASNA230BMASNA-T1

MASNA230AMASNA-T2

MOSES230

MMS2

CHTAUG765

LAFAYETTE

Asymmetric Power System

ModelNew York Power

Authority


Synchronized Measurement Based SEWhat is the Advantage

va(t)ia(t)

vA(t)iA(t)

vb(t)ib(t)

vB(t)iB(t)

vc(t)ic(t)

vC(t)iC(t)

Voltage Waveform Measurement

Current Waveform Measurement

Bus 1 Bus 2

a

b

c

A

B

C

Phasor Measurements of Voltages and Currents


SE with Synchronized Measurements

* * * Direct Solution * * * * * * Direct Solution * * *

⎥⎦

⎤⎢⎣

⎡

−+

=⎥⎦

⎤⎢⎣

⎡⎥⎦

⎤⎢⎣

⎡− real

Timagimag

Treal

imagTimagreal

Treal

imag

real

WzHWzHWzHWzH

xx

ABBA

rWrMin H ~~

xHzrtoSubject ~~~~: −=

imagT

imagrealTreal WrrWrrMin +

imagimagrealrealrealreal xHxHzrtoSubject −−=:

realimagimagrealimagimag xHxHzr −−=


In Case that All Data are GPS Synchronized Measurements the

State Estimator is DIRECT

Big Advantage

Observation


Detection of SE Bias

Case Description Confidence Level(Chi-Square Test)

Three Phase Asymmetric Model,Three Phase Measurements

100.00

Three Phase Symmetric Model,Three Phase Measurements

13.02

Three Phase Asymmetric Model,Single Phase (A) Measurements

0.0

Numerical Experiments on the MSU-1 Line (765 kV)


G G G G G G G G G G

G G G G G G G G

G G G G G G

G G G G

G G

SOURCE BUS001 BUS002 BUS003 BUS004 BUS005 BUS006 BUS007 BUS008 BUS009 BUS010

ASOURCE ABUS001 ABUS002 ABUS003 ABUS004 ABUS005 ABUS006 ABUS007 ABUS008

BSOURCE BBUS001 BBUS002 BBUS003 BBUS004 BBUS005 BBUS006

CSOURCE CBUS001 CBUS002 CBUS003 CBUS004

DSOURCE DBUS001 DBUS002

Investigation of SE Biases viaNumerical Experiments

Approach: Systems of Variable Size

Observations: System Imbalance StabilizesPhase with Max Voltage: RandomEffects on Mega RTO SE: Unknown

Observations: System Imbalance StabilizesPhase with Max Voltage: RandomEffects on Mega RTO SE: Unknown


Confidence Level vs size for single phase mesurements

0.0001

0.001

0.01

0.1

10 5 10 15 20

System Size

Con

fiden

ce L

evel

σ=0.02 σ=0.01 σ=0.009 σ=0.008 σ=0.007

Confidence Level of Data Accuracy


GPS Synchronized Measurements are Imperfect – Errors are PresentOther Useful Data Exist (SCADA, Relays, DFRs, etc.).

Proposed Approach: HYBRID STATE ESTIMATOR. It Utilizes all Available Data

Errors from ImbalanceErrors from Asymmetry

Proposed Approach: THREE PHASE MODEL. It Eliminates Model Biases

Proposed Approach


A B C

Bus m

A B C

Bus kA B C

A B CVk~

Vm

~

~Id1,k,A

Pd1,k,A

Qd1,k,A

~Id1,m,APd1,m,AQd1,m,A

device d1

device d2

~Id2,k,A

Pd2,k,A

Qd2,k,A

QPF-SE Approach: Available Data

Phasor Measurements Non-Synchronized Measurements

Description Type Code Description Type

Code

Voltage Phasor, V~ 1 Voltage Magnitude, V 4

Current Phasor, I~ 2 Real Power Flow, fP 5

Current Injection Phasor, injI~ 3 Reactive Power Flow, fQ 6

Real Power Injection, injP 7

Reactive Power Injection, injQ 8


Kentucky

Tennessee

SUB

SUB

SUB

G G

SUB

G G

SUB

SUB

SUB

G G

SUB

G G

SUB

G G

SUB

G G

SUB

G G

G G

G G

SUB

SUB

SUB

G G

SUB

SUB

SUB

SUB

SUB

SUB

G G

SUB SUB

G G

G G

G G

G G

G G

G G

SUB

G G

SUB

SUB

Section 2Section 1 Section 3 Sect

Section 5 Section 7Section 6

BROWNSFERMADISON

WIDOWSCRK

LIMESTONE

WESTPOINT

BFTRIN2BFTRIN1

MAURY

UNION

BRFTRIC1BRFTRIC2

EASTPOINT

MILLER

TRICOTRINITY

RACOONMT

SEQUOYAH

JOHNSONVLDAVIDSON

CUMBERLND

JACKSON

GLEASON

FRANKLIN

MARSHALL

MONTGOMRY

WILSON

ROANE

PARADISE

WATTS-BAR

VOLUNTEERBULL-RUN

PHIPSBENDSULLIVAN

WVERNONLOWNDES

PLEASANTH

CORDOVA

BENTON

FREEPORTBIRMSTEEL

SHELBY

LAGOONCRK

ARKANSAS HAYWOOD

WEAKLEY

SHAWNEE

PINHOOK

NAGEL

SHAVENCONASAUGA

CALEDONIA

POCKET

LOANOAK

QPF-SE Approach: Three Phase Model of the 500 kV Transmission System, TVA


3-Phase Overhead Transmission Line Accept Cancel Franklin to Sequoyah 500 kV Line

Phase Conductors ACSRSize RAIL

Shields/Neutrals HS5/16HS

Tower/Pole TVA-SA-23R1Circuit Number 1

Tower/Pole Ground Impedance (Ohms)25.0 0.0R =

Bus Name, Side 1

62.77Line Length (miles)0.1Line Span Length (miles)

100.0Soil Resistivity (Ohm-Meters)

X =

FRANKLINBus Name, Side 2

SEQUOYAHCircuit Number

1

A1 B1 C1

N1 N1

110.0 feet

80.0'

SINGLE TOWER 500 KV

Type

SizeType

Type

N/AStructure Name

500.0Operating Voltage (kV)2300.0

Insulation Level (kV)FOW (Front of Wave)

BIL (Basic Insulation Level) 1650.0

AC (AC Withstand) 1050.0 Transposed Phases Insulated Shields Transposed Shields

Program WinIGS-F - Form IGS_M102


QPF-SE Approach: Hybrid SE Formulation

∑∑−∈∈

+=synnonphasor

JMinν ν

νν

ν ν

νν

σηη

σηη

22

* ~~

νν η~~~~,, +−= NkAk VVz

ννν ηη ~

~~~~~~

~~

,

,

,

,

,

,

,,1,,1 +

⎥⎥⎥⎥⎥⎥⎥⎥

⎦

⎤

⎢⎢⎢⎢⎢⎢⎢⎢

⎣

⎡

=+=

Ck

Bm

Am

Ck

Bk

Ak

TAkdAkd

VVVVVV

CIz

=+−= νν η2~~ 2

,, NkAk VVz

ννν ηη +

⎪⎪⎪⎪

⎭

⎪⎪⎪⎪

⎬

⎫

⎪⎪⎪⎪

⎩

⎪⎪⎪⎪

⎨

⎧

⎟⎟⎟⎟⎟⎟⎟⎟

⎠

⎞

⎜⎜⎜⎜⎜⎜⎜⎜

⎝

⎛

⎥⎥⎥⎥⎥⎥⎥⎥

⎦

⎤

⎢⎢⎢⎢⎢⎢⎢⎢

⎣

⎡

=+=

*

,

,

,

,

,

,

,,1,,,1

~~~~~~

~Re

Ck

Bm

Am

Ck

Bk

Ak

TAkdAkAkd

VVVVVV

CVPz

GPS-Synchronized Measurements(Linear Model)

Non-Synchronized Measurements(Quadratic Model)

Voltage Phasor

Current Phasor Real Power

Voltage Magnitude

( ) ( ) νη22

,,,,2

,,,, +−+−= iNkiAkrNkrAk VVVV


Error of Bus Voltage Phase – Estimated minus Measured ValueMagnified 200 times (min error: -0.144, max error: 0.147 degrees)


Bad Data Detection & Identification

This is an Important Issue:

- Current Approaches are Computationally Demanding.- Leverage Points Are Especially Troublesome.

Utilizing All Available Data Increases Redundancy.

The implications are:(a) Increased Effort for System Initial Calibration, and (b) Improved Bad Data Identification Process.

Visualization Methods Also Help


Error of Bus Voltage Magnitude and Phase – Estimated minus Measured ValueMagnitude is Normalized (min magnitude error: 0, max magnitude error: 0.141)Phase is Magnified 200 times (min phase error: -0.672, max phase error: 0.165)

There is one bad DatumCan you find it?

There is one bad DatumCan you find it?


Error of Bus Voltage Magnitude and Phase – Estimated minus Measured ValueMagnitude Error Range: 0.1 to 4.4kV – Phase Error Range: -0.1 to 0.8 Degrees

(Phase Error is Magnified 100 times)

Measurement Data: Phase A OnlyRandom Error: Voltage: 0.7%, Phase: 0.050, Power: 1%

Displayed Data:

Phase A





Displayed Data:

Phase B





Displayed Data:

Phase C


Proposed Utilization of the QPF-SE

• Assume There Are Sufficient GPS Synchronized Measurements for Complete State Observability from These Measurements Alone

• Exercise QPF-SE Once Each Hour

• Use Results of QPF-SE to Calibrate GPS Synchronized Measurements.

• Use the GPS Synchronized Measurements Directly as the Real Time Model.


Summary and ConclusionsPresent Implementation of State EstimatorsBiased Estimator

Synchronized Measurements Direct State Estimation

Synchronized Measurements + Multiphase ModelUnbiased State Estimation

Synchronized Measurements+SCADA+IEDs + Multiphase ModelHybrid, Unbiased State Estimation


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role of gps synchronized measurements in power system ... · role of gps synchronized measurements...

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