Outline Introduction to Synchrophasors Measuring Synchrophasors - - PowerPoint PPT Presentation

Phasor Measurement Unit

and Applications ¡ ¡ ¡ ¡

Akanksha Pachpinde

¡

Outline

§ Introduction to Synchrophasors § Measuring Synchrophasors using PMU § Terms associated with PMU § PMU architecture § Applications of PMU

§ Monitoring § Protection § Control ¡

Introduction to Synchrophasors

An AC waveform can be mathematically represented as: In phasor notation it can be represented as:

where: ¡ ¡ = ¡rms ¡magnitude ¡of ¡waveform ¡ ¡ = ¡phase ¡angle ¡

Measuring Synchrophasors using PMU

• Anti aliasing filter – restricts bandwidth of signal to satisfy sampling

theorem

• GPS time tagging – provides a time stamp for the signal
• Phase locked oscillator – keeps frequency of the reference and measured

signal equal

Terms associated with PMU

• Time tagging:

– 8 bit message – 4 bits SOC, 3 bits fraction of second, 1 bit quality

• Synchronized reporting:

– Reporting rate must evenly divide 1 second interval (IEEE standard)

• Total Vector Error:

where Xr and Xi represent theoretical synchrophasor and Xr(t0) and Xi(t0) represent measured values

Example of PMU Architecture

PMU applications - Monitoring

1. Digital System Disturbance Recorder: § First recorded wide are measurements in 1992 § After 1996 and 2003 blackouts EIPP formed (now known as NASPI) § Low frequency oscillation detection and oscillation source detection § Phase angle difference and voltage stability detection § Post mortem analysis § High cost led to development of concepts such as depth of

• bservability

2. For State Estimation: § Prior state only estimated from power flow measurements § Using synchrophasors state can be measured as complex bus voltages can be measured § No longer have to assume that the system is static during the scan

PMU applications – Protection and Control

Control of Backup Relay performance § False tripping of relays might occur during system disturbances § PMUs can be used for supervisory control of distance relays to overcome this problem Adaptive out-of-step protection § Out-of-step relays used to determine if the generators are going out of step § Become outdated quickly in a highly interconnected network § Wide-area measurements of positive sequence voltages and swing angles can directly determine stability

Security- dependability § Failure modes of relay- trips when it should not or fails to trip when it should § False trips can aggravate disturbances in a highly stressed system § Supervisory control can ensure that more than one relay sees a fault before breaker is actuated Improved control § Control can be based on measurement values of remote quantities § System can react to threatening situations with employing continuous feedback control § Addition of PMU controllers to local controllers will add robustness ¡ ¡

PMU applications – Protection and Control

Questions ?

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