What factors affect the stability of a power system? - Blog

Numerous factors influence the stability of power systems; according to authoritative public sources, these can be categorized into the following groups:

I. System Operation and Structural Factors

Generator Output Variations: Sudden changes in generator output power (such as those caused by faults or control failures) disrupt the system's power balance, triggering instability in frequency or power angle.

Load Variations: Instantaneous increases or decreases in load lead to an imbalance between supply and demand, potentially causing frequency fluctuations, voltage dips, or even voltage collapse.

Transmission Line Parameters: Excessive line resistance results in voltage drops and power losses, while line reactance influences power transfer limits and static stability.

Grid Structure: Factors such as a weak network structure, long-distance heavy-load transmission, and electromagnetic loops can all compromise overall system stability.

II. Equipment and Control Factors

Relay Protection and Automation Systems: Delays in protective actions or maloperations may exacerbate the scope of a fault; furthermore, improper parameter settings for control equipment-such as excitation systems, PSS (Power System Stabilizers), and governors-can compromise dynamic stability.

FACTS and Energy Storage Devices: Technologies such as STATCOM (Static Synchronous Compensators), SVCs, and series capacitor compensation can enhance system stability; however, improper configuration of these devices may also introduce new risks.

Grid Integration Characteristics of New Energy Sources: Inverter-based power sources-such as wind and photovoltaic systems-lack inherent inertia, thereby diminishing system damping and increasing the risk of instability under small disturbances.

III. External Environment and Disturbing Factors

Weather Conditions: Extreme weather events (such as lightning strikes, icing, high temperatures, and typhoons) can lead to equipment failure, line tripping, or power output fluctuations.

Major Disturbances: Significant disturbances-such as short-circuit faults, line tripping, or the sudden disconnection of generators or transformers-may trigger transient instability.

Variations in Wind Speed and Temperature: Wind speed directly affects wind power output; temperature alters line resistance and equipment heat dissipation capabilities, thereby indirectly influencing system stability.

IV. Key Factors Influencing the Stability of Each System Classification

According to IEEE/CIGRE standards and my country's *Guidelines for Security and Stability of Power Systems* (DL 755-2001), power system stability is classified into three categories, each predominantly influenced by distinct factors:

Power Angle Stability: Influenced by generator synchronizing torque, damping torque, electrical distance, and the initial operating point; following a major disturbance, it is prone to non-periodic or oscillatory loss of synchronism.

Voltage Stability: Influenced by the balance between reactive power supply and demand, load characteristics, and the response speed of on-load voltage regulation equipment; voltage collapse is more likely to occur in high-load regions.

Frequency Stability: Influenced by active power imbalance, rotating reserve capacity, and load-frequency characteristics; a frequency collapse may be triggered in the event of a significant power deficit.

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In summary

Power system stability is the result of the coupled interaction of multiple factors and requires comprehensive assurance across various levels, including planning, operation, control, and emergency response.