Real-Time Voltage Stability Monitoring Voltage Stability... · Measurement-based indicators: ... o Calculates Q-margin & other indices for proximity to collapse ... comprehensive

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Smart Solutions, Practical Results

Real-Time Voltage Stability Monitoring

Damir NovoselPresident, Quanta Technology LLC

JSIS MeetingTempe, Arizona

January 15-17, 2013

Voltage Stability Assessmentx

Under‐voltage signal

#1

#2

r

Voltage instability region

#1: Inaccurate under‐voltage detection#2: Under‐voltage fails to detect

Dynamic, model-based simulation tools:• Voltage Stability Assessment (VSA) based on

State Estimation contingency analysis• Tracking the relative distance from voltage

instability continually in real-timeo Distance to the nose of the PV curve o State Estimation based stability boundary

• Important to validate model correctness

Measurement-based indicators:• Monitor available reactive power levels

(capacitor/reactor reserves, tap-changers)• Singular Value Decomposition (SVD)• Sensitivity analysis• Distance of the load's apparent impedance to

the Thevenin impedance - VIP, REI equivalent, Real-time Voltage Instability Indicator (RVII)Source: ABB

Accuracy Easy to Interpret  Data Req. Comput.

BurdenLocal/ WA/

FIDVRRVII or VIP improved^ Low/Mod.* High Very low Very low L/WA/FID.

VIP^ Low Mod./High Very low Very low L/WA

REI^ Low Mod./High Low Low L/WA

SVD Mod./High Moderate Moderate Moderate WA

Sensitivity  Moderate Moderate Low Low L/WA

Time Series Moderate Moderate Low Low/Mod. WA

* Low – far from stability boundary; Moderate – close to stability boundary^ Pilot  or Product Installation WA – Wide Area

Model‐Free

High-Level Method Assessment

Accuracy Easy to Interpret  Data Req. Comput.

BurdenLocal/ 

WA/ FIDVR

RT Nomogram**^ High High High Mod./High WA

Contingency VSA^ High High High High WA/FIDVR

Cont. Power Flow^ Mod./High High High High WA

Reactive Reserve^ Moderate Moderate Mod./High Moderate L/WA

Decision Trees High Moderate High High/Low** WA

Sensit./Eigenval. High Moderate High Mod./High WA

** Two dimensional, SCADA/SE updated or multi‐dimensional RT VSA *** High in offline training; Low in real‐time^ Pilot  or Product Installation WA – Wide Area

Model‐Based

High-Level Method Assessment

RVII/VIP Improved Advantages• Model-free, fast real-time voltage instability detection

method*, independent of state estimation• Implementation in several variants: bus, load center,

transmission line, transmission corridor o Calculates Q-margin & other indices for proximity to collapseo Stability boundary

calculated with real-time PMU data refresh rate

• Easily combined with other methods/indices o Reactive power monitoring o Could initiate model-based

contingency analysis(e.g., by alarming the operator)

New Q‐Margin Loading margin

RVII/VIP Improved Advantages• Ability to process data from different sources (PMUs,

SCADA, simulation outputs (static and dynamic)o Takes immediate advantage of available PMUso Scales up well with increased number of PMUs

• Excellent results from actual system tests o Slowly changing system operating conditions (load ramp) o Tracking system dynamics after disturbances

• Able to distinguish FIDVR even if voltage is very low

• Simple implementation in Control Center tools and/or local IEDs for: o Operator tools to increase

situational awarenesso Local automated actions o Addition to SIPS

Source: BPA

Extracting More Information from RVII

Source: PG&E

• Increased observability improves accuracy• Managing loss of PMU data

Extracting More Information from RVII

• Flags indicating breaker status• Incorporate switching, e.g. bypassing capacitors

Source: PG&E

Test Result SummaryComprehensive tests using real-life PMU and SCADA measurements and off-line time-sequence simulation tools:• Performance improves with additional information

o Design consideration on where to install and what to measure

• Ability to detect instability even if voltage close to nominalo Load centers, transmission lines, and corridorso Highly-meshed high voltage systems more challenging

• Results comparable to detailed, model-based off-line QV analysis; very accurate closer to instability boundary

• Discriminates between FIDVR and fast voltage instability• No false alarms

• Customized visualization tool for monitoring voltage instability running at the SCE's Advanced Technologies Center

• Using real-time phasor streaming data

Source: SCE

SCE Pilot Installation

• Deployment efforts as part of comprehensive WAMPAC o At PG&E integration with Alstom e-terravisiono With BPA - Pilot installation with Space Time Insight STAS

• Design monitoring and control strategies

Present & Future Activities

NewMEASUREMENT-BASEDVOLTAGE STABILITYRVII Methodology

Other Indices

TraditionalMODEL-BASED

VOLTAGE STABILITYAnalysis

(EMS)

SCADA& Alarms WAMS

State Estimator

StateMeasurement

Other EMSApplications

New Applications

Small SignalStability

OscillationMonitoring

Transient & Voltage Stability

StabilityMonitoring& Control

IslandManagement

Island Detection, Resynchronization,

& Blackstart

New Real-time Voltage Instability Indicator Solution

Alstom e-terravision

approach with RVII

• Different methods have different advantages and users should select methods optimal for their systemo None is suitable for all systems and all possible

manifestations of instability, measurement configurations, etc.

• Real-time, model-free methods are faster but generally less accurate – Good for trend and status monitoring

• Combination of selected methods provides comprehensive solution for voltage stability issues

• Real-Time Voltage Instability monitoring technology is needed as a part of the overall solution

• Importance of integration and coordination at WECC

Summary