Power Systems ARTS

Power Systems Analysis, MonitoRing, ConTrol and Simulation

Real-time voltage stability monitoring for transmission system operators.

Discuss a project Explore our services

Live deployment

Voltage stability monitoring running in the national control centre of the Hellenic Interconnected System.

Patented method

The relay-based LIVES index, granted as patent GR 1009503 B by the Hellenic Industrial Property Organisation.

Research origin

Developed in the Electrical Energy Systems Laboratory of the National Technical University of Athens.

What we do

Three ways to see instability coming

Offline study, online measurement, and the integration work that puts either one in front of an operator.

Simulation

WPSTAB

Quasi-steady-state simulation for long-term voltage stability: PV and QV curves, sensitivities and eigenvalues.

The WPSTAB software

Measurement

NLI & RLI stability indices

Early warning of voltage instability, from PMUs at EHV buses or from the distance relays already on your lines.

How the indices work

Integration

Control-centre delivery

EMS and WAMS integration, operator training and support, and steady-state and dynamic power system studies.

Our services

How it works

Watching a collapse arrive

A corridor is loaded a little harder, minute by minute, and its voltage declines slowly. The index falls as the operating point approaches the nose of the curve, the point of maximum loadability with no stable operating point beyond it, and it crosses zero there. In service, warning and alarm thresholds set above zero sound earlier, minutes before the voltage collapses, which is what gives an operator time to act.

Operating pointMoving down the PV curve to the nose
Bus voltageDeclining slowly, then collapsing
Stability indexFalling to zero at the nose
Stable

An illustration, not a measurement. The axes carry no values and nothing here identifies a real network.

Deployment

Voltage stability monitoring at the Hellenic national control centre

PS ARTS developed and installed a software tool in the control centre of the Hellenic Interconnected System that indicates proximity to long-term voltage instability from synchronised phasor measurements taken at a sparse set of PMUs. The application covers signal sampling and filtering, index computation and the operator-facing display, and its output has been checked against a real system incident.

  • SystemHellenic Interconnected System
  • InputSynchronised phasor measurements, sparse PMU placement
  • IndexNew LIVES Index (NLI)
  • PresentedPAC World Conference, Athens 2024
Read more
Plot of the New LIVES Index against time for three EHV buses. All three traces start above zero and cross below it at around eighty seconds, marking the onset of long-term voltage instability.
Simulated case — NLI at three EHV buses, crossing zero at instability

Recent work

Presentations and publications

PAC World · 2024

Implementation of Real-Time, PMU-Based, Long-Term Voltage Stability Monitoring

Application structure, interface and filtering, with indicative results following an actual system incident.

 IEEE PES GM · 2022

Long-term Voltage Stability Wide-Area Control using PMU Measurements

Wide-area control driven by the online voltage instability indices NLI and RLI.

 IEEE PES T&D LA

Voltage Stability Support by Wind Farms

Keynote given by Emeritus Professor Costas Vournas at the IEEE PES Transmission and Distribution Conference, Latin America.

Considering stability monitoring for your network?

Tell us about the system and what you need to see. We will tell you honestly whether our indices are the right instrument for it.

Start a conversation