Power System Stability Studies

What are Power System Stability Studies?

• • • Power system stability studies focused on the system’s ability to maintain synchronous operation following a severe disturbance.

    • Based on the physical nature of the phenomena, power system stability is classified as rotor angle stability, frequency stability, and voltage stability. Based on the size of the disturbances, power system stability can be classified into steady-state/dynamic stability, and transient stability.

    • Steady State Stability is the ability of the power system to maintain synchronism under small and slow disturbances (e.g., gradual power changes). Dynamic Stability is an extension of steady-state stability. It is concerned with small disturbances lasting for a long time with the inclusion of automatic control devices.

    • Transient Stability is the ability of the power system to maintain synchronism when subjected to a severe disturbance (e.g., short circuit, sudden outage of line, sudden application, or removal of loads).

    • The most common disturbances that produce instability in industrial power systems are short circuits, loss of generation, load, and connection with utility, starting a motor with a large capacity, and switching operations.

    • Power system stability studies can be used to determine the rotor angle, torque, and speed of synchronous machines, real and reactive power flow, bus voltage magnitude and angle, bus frequencies, torque and slip of induction motors under power system disturbances. Also, this study can be used to calculate the critical clearing angle and time.

What is the Importance of Power System Stability Studies?

The main purpose of power system stability studies is:

• Power system planning and design: To decide future transmission network requirements, equipment specifications, and selection of parameters for control and protective systems.

• Power system operation: To determine operating limits and determine the need for arming emergency controls or special protection schemes.

• Post-disturbance analysis: To simulate events following major system disturbances or blackouts.

How Do We Perform Power System Stability Studies?

• Step-1: Data collection such as single line diagram (SLD), system data, transformers, lines/cables, reactors, loads, synchronous generator, induction machine, disturbance data, study parameters, etc.

• Step-2: Modeling the study system using PSCAD/EMTDC software.

• Step-3: Preparation of simulation case studies with the study scenarios accepted by the clients.

• Step-4: Preparation of technical report and submission to clients.

What Standards can be Referred for Power System Stability Studies?

• IEEE Std 1110™-2019 - IEEE Guide for Synchronous Generator Modeling Practices and Parameter Verification with Applications in Power System Stability Analyses.

• IEEE Std 399-1997 - IEEE Recommended Practice for Industrial and Commercial Power Systems Analysis.

• Prabha Kundur – Power system stability and control.

• Hadi Saadat – Power System Analysis.