voltage security and out-of-step protection using ... 1/42 stockholm – april 18, 2013 workshop on...

Stockholm – April 18, 2013 G.N.Taranto 1/42

Workshop on Resiliency for Power Networks of the Future

Voltage Security and Out-of-Step Protection Using Synchrophasors

Prof. Glauco N. Taranto, Ph.D.

COPPE/UFRJ Programa de Engenharia Elétrica



Acknowledgements Acknowledgements



2008 / 2 Curso COE754 - Glauco Taranto 3

ESTABILIDADE DE SISTEMAS DE POTÊNCIA

Capacidade de permanecer em equilíbrio operativo

Equilíbrio entre forças em oposição

ESTABILIDADEANGULAR

ESTABILIDADE DE TENSÃO

ESTABILIDADE APEQUENAS

PERTURBAÇÕES

ESTABILIDADETRANSITÓRIA

ESTABILIDADEMID-TERM

ESTABILIDADELONG-TERM

GRANDESPERTURBAÇÕES

PEQUENASPERTURBAÇÕES

Capacidade de manter sincronismo

Equilíbrio de torques nas máquinas síncronas

Grandes perturbações

Primeiro swing

Estudos até 10 s

Capacidade de manter perfil de tensãoaceitável em regime permanente

Balanço de potência reativa

Perturbações severas

Grandes excursões de tensão e freqüência


Eventos chaveados

Dinâmica de OLTC ecargas

Coordenação deproteção e controles

Relações PxV e QxV emregime permanente

Margem de estabilidade

Reserva de reativo

Ponto de Colapso

Métodos LinearesINSTABILIDADE

APERIÓDICAINSTABILIDADEOSCILATÓRIA

Torque de sincronismoinsuficiente

Dinâmica rápida e lenta

Período de estudo devários minutos

Freqüência do sistemaconstante e uniforme

Dinâmica lenta

Período de estudo dedezenas de minutos

MODOS INTER-ÁREASMODOS LOCAIS MODOS DE CONTROLE MODOS TORSIONAIS

Torque de amortecimento insuficiente

Ação de controle desestabilizante

Métodos Lineares

Voltage

Stability

Long-term

Power System Stability

Frequency

Stability



2008 / 2 Curso COE754 - Glauco Taranto 4

ESTABILIDADE DE SISTEMAS DE POTÊNCIA

Capacidade de permanecer em equilíbrio operativo

Equilíbrio entre forças em oposição

ESTABILIDADEANGULAR

ESTABILIDADE DE TENSÃO

ESTABILIDADE APEQUENAS

PERTURBAÇÕES

ESTABILIDADETRANSITÓRIA

ESTABILIDADEMID-TERM

ESTABILIDADELONG-TERM

GRANDESPERTURBAÇÕES

PEQUENASPERTURBAÇÕES

Capacidade de manter sincronismo

Equilíbrio de torques nas máquinas síncronas


Primeiro swing

Estudos até 10 s

Capacidade de manter perfil de tensãoaceitável em regime permanente

Balanço de potência reativa

Perturbações severas

Grandes excursões de tensão e freqüência


Eventos chaveados

Dinâmica de OLTC ecargas

Coordenação deproteção e controles

Relações PxV e QxV emregime permanente

Margem de estabilidade

Reserva de reativo

Ponto de Colapso

Métodos LinearesINSTABILIDADE

APERIÓDICAINSTABILIDADEOSCILATÓRIA

Torque de sincronismoinsuficiente

Dinâmica rápida e lenta

Período de estudo devários minutos

Freqüência do sistemaconstante e uniforme

Dinâmica lenta

Período de estudo dedezenas de minutos

MODOS INTER-ÁREASMODOS LOCAIS MODOS DE CONTROLE MODOS TORSIONAIS

Torque de amortecimento insuficiente

Ação de controle desestabilizante

Métodos Lineares

Angular

Stability

Transient

Stability

Frequency

Stability

Power System Stability



Voltage Instability Identification

PART I



  Voltage Stability

  Short term

â From miliseconds to a few seconds

â Large perturbation

â Induction motor starting, HVDC

  Long term

â From seconds to many minutes

â OLTC, OEL

â Manual intervention may be possible

Introduction Introduction

Work Focus



LThThLThTh

ThLTh

L QEXPXEXQEV −−±−= 2242

42

The Static “Nose” Curve (P-V)



Background

  The method is based on:

  Measurements of voltage and current phasors

  Thevenin equivalent

  Impedance matching

Background



Background (Thevenin)

LThThL IZEV!!!

−=

ThL ZZ =

1 equation

2 unknowns

Maximal power

transfer

Background



VIP – Voltage Instability Prediction

Source: K. Vu and D. Novosel, “Voltage Instability Predictor (VIP) - Method and

System for Performing Adaptive Control to Improve Voltage Stability in Power

Systems,” US Patent No. 6,219,591, April 2001.

Finding: relying only on voltage magnitudes

to detect voltage instability is neither helpful

nor reliable!

Background



Fundamentals

⎟⎠⎞

⎜⎝⎛= −

Th

L

EV θβ coscos 1

0≈ThRassuming Eth is

unknown Methods already proposed:

1)   LMS

2)   Tellegen´s Principle

Fundamentals



Conceptual Analysis

Step Known Variables Estimated Variables

ZL(Ω) IL(A) VL(V) ETh(V) ZTh(Ω) ETh(V) ZTh(Ω)

1 9 2 18 21 1,5 19 0,5

2 8 2,22 17,76 21 1,46 19 0,56

20 V (?)

1 Ω (?)

LVIL ZL

Hint!

Eth = 20 V

Zth = 1 Ω

Fundamentals



Proposed Algorithm

Step 1 – Estimate the initial value of Etho

Step 2 – Compute Xtho

Step 3 – Compute Eth(i) according to the logics of

the previous numerical example

Step 4 – Compute Xth(i) given Eth

(i)

Step 5 – Increment (i) and return to Step 3.

Proposed Algorithm



Simulation Results

  The proposed algorithm was applied to the entire Italian System from

real data

  System Characteristics:

  2549 buses (380 kV and 220 kV networks)

  2258 transmission lines and transformers

  325 generators

  50 GW of load

  Dynamic models for OLTCs, OELs, voltage regulators and speed governors

  Application to load and “transit” buses

  Sampling rate – 20ms (1 phasor/cycle in 50Hz)

Results



380 kV Network

Milan

Florence

Results



Brugherio 380kV Bus Results



It is being tested with actual PMU data

Hasle

SwedenNorway

BRAZIL NORWAY

  Voltage colapse has not occured so far. The effectiveness of the algorithm is yet to be proved.



Concluding Remarks   The phasor measurements can efficiently be utilized in voltage

instability prevention.

  High sampling rates are necessary.

  Prediction of voltage instability in a region can be made without

extensive use of the communications resources.

  It is possible to proposed more sophisticated control logics relying on

data synchronization via GPS.

  Comprehensive simulating results with the Italian System and

preliminary measured results with the Brazilian System encourage

further research on this topic.

Concluding Remarks



Future needs

I

I

V

I

Results



Out-of-Step Protection

PART II



Mo#va#on   The Uruguayan Power System

• Peak load of 1.7 GW (80% in great Montevideo)

• Gen. capacity 2.6 GW (53% hydro, 47% thermal)

l  Hydro generation mostly in the North

l  Thermal generation concentrated in South



Mo#va#on (cont.)

  Outages in two 500 kV lines (Palmar – Montevideo)

l  Can lead the system to a complete blackout

l  Fast controlled N-S separation by opening the 150 kV network,

plus fast load shedding in the South



Objec#ve

  The comparison of three emergency protec#on strategies to maintain the system in opera#on with the smallest amount of load curtailment.



Out-of-step Protection

  Unstable electromechanical oscillations   Can appear after a large disturbance   OOS protection can be done with conventional distance

relays

24

ZA ZL ZB

VC VD

ILEB 0EA δ

( )AZjLZBZAZ

LICV

CZ −⎟⎠⎞⎜

⎝⎛ −

++==

2cot1

2δ



Out-of-step Protection

25

Electrical Center (EC)

l  Power Swing Blocking (PSB)

l  Out-of-Step Tripping (OST)



Out-of-step Protection (cont.)

26

ZR = ZA

ZS = ZB



The Strategies

  Strategy#0 – Load shedding in the South subsystem;   Strategy#1 – Controlled Islanding and load shedding with local measurements;   Strategy#2 – Controlled Islanding and load shedding with synchrophasor measurements.



Strategy #0

  This is the strategy in opera#on today;   The system remains connected with one synchronous island through the 150 kV network;   A very large amount of load is shed.



Strategy #1

  Islanding scheme (IS) applied to pre-‐selected network loca#ons, preferably near the electrical center. IS performed by installing OST func#ons in the preselected loca#ons;

l  A less amount of load is shed.



Strategy #2

  Controlled Islanding and load shedding with synchrophasor measurements;   Power Swing Detec#on (PSD) and Predic#ve Out-‐Of-‐Step Tripping (OOST) algorithms patented by Guzman-‐Casillas and Schweitzer Engineering Laboratories, Inc. (SEL).

l  A lesser amount of load is shed.

VPalmar

VMontevideo



The Fundamentals of SEL’s Patent

  U#lizes:

  Displacement – Speed – Accelera#on

 (θPalmar – θMontevideo) = δ

 δ x δ • 



SEL’s Patent – PSD



SEL’s Patent – OOST



Quan#ta#ve Analysis of Transient Response in the A-‐S Plane

S [Hz]

A [Hz/s]

M1

M2

M3

z3 z2 z1 s0 s1 s2m0

m1

m2

S [Hz]

A [Hz/s]

z1 s0

m0



Simula#on Results

  The scenario under study is one with maximum thermal genera#on with some hydro units in service. The scenario assumes that one of the 500 kV Palmar-‐Montevideo TL is out of service and a 3-‐phase fault occurs at the remaining 500 kV line in the Montevideo end.

  The clearance #mes used were:   t=60ms (3 cycles) for the near end

  t=80ms (4 cycles) for the far end



Simula#on Results for Strategy #1



Simula#on Results for Strategy #2

-0.5 0 0.5 1 1.5 2

-2

-1

0

1

2

3

4

S [Hz]

A [H

z/s]

A

B

CD

E

F

O



Load Shedding

Strategy #0 Strategy #1 Strategy #2

600 MVA 496 MVA 416 MVA

100% 82,7% 69,3%

1/3 of Uruguay total load



Conclusions (1/2)

  Two strategies for controlled islanding of the Uruguayan power system were presented: one using only local measurements and the other using synchrophasors.

  Simula#on results showed that controlled islanding of the North-‐South #e with fast load shedding with both strategies performed significantly beger than the current u#lity prac#ce.

  The necessary load shedding was reduced by 17% when the PSB-‐OST scheme (using only local signals) was u#lized, and by 31% when the OOST scheme (using synchrophasor measurements).



Conclusions (2/2)

  The strategy that uses synchrophasor measurements is more agrac#ve since it is able to curtail less amount of load, due to its predic#ve capability. However, the strategy that uses only local signals should not be discarded since it provides a simple and cost-‐effec#ve solu#on to the problem. It also has the advantage that it can be implemented with the current protec#on system already in place.



For further reading

  R. Franco, C. Sena, G. N. Taranto & A. Giusto, “Using Synchrophasors for Controlled Islanding – A Prospective Application for the Uruguayan Power System”, IEEE Transactions on Power Systems, Vol. 28, No. 2, pp. 2016-2024, May 2013. DOI 10.1109/TPWRS.2012.2224142

  S. Corsi & G. N. Taranto, “A Real-Time Voltage Instability Identification Algorithm Based on Local Phasor Measurements,” IEEE Transactions on Power Systems, Vol. 23, No. 3, pp. 1271-1279, August 2008. DOI 10.1109/TPWRS.2008.922586

Voltage Instability Identification

Out-of-Step Protection


Workshop on Resiliency for Power Networks of the Future Rio de Janeiro

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voltage security and out-of-step protection using ... 1/42 stockholm – april 18, 2013 workshop on...

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