Analysis of Operation, Maintenance and Fault Handling Methods for Power Capacitors in Substations

Discussion on Operation, Maintenance, and Fault Management of Power Capacitors

Power capacitors play a vital role in power systems by improving voltage quality and enhancing operational efficiency and economic performance. However, during long-term operation, they may experience various failures that affect their performance and reliability, potentially threatening the safety and stability of the entire system. Therefore, in-depth study of their operation, maintenance, and fault handling is essential to ensure the reliable operation of substation equipment and to support the safe, stable, and economical operation of power systems.

The fundamental principle of power capacitors is based on their energy storage capability. Composed of two conductive plates separated by a dielectric medium, a capacitor stores electric charge when voltage is applied, creating an electric field. As system voltage fluctuates, the capacitor releases or absorbs energy, enabling dynamic voltage regulation. This characteristic allows capacitors to stabilize voltage, reduce fluctuations and flicker, improve power factor, compensate for reactive power, and reduce grid losses—thereby enhancing both system stability and economic efficiency.

In practice, power capacitors are susceptible to various faults, including insulation breakdown, abnormal temperature rise, leakage current, mechanical failure, and reduced insulation resistance. These issues stem from a combination of factors. Design and manufacturing defects—such as substandard materials, poor sealing, or inadequate welding—can compromise reliability. Operational conditions also play a critical role: prolonged overvoltage or overload can cause internal overheating and accelerate insulation aging; humid, polluted, or high-temperature environments may degrade insulation performance; mechanical vibration or improper installation can lead to loose connections or structural fatigue. Additionally, dielectric aging, cumulative partial discharge, and contamination can gradually weaken electrical performance, eventually leading to failure.

To ensure reliable operation, effective maintenance strategies are essential. Routine maintenance should integrate intelligent monitoring—using IoT sensors to collect real-time data on voltage, current, temperature, and harmonics—enabling condition awareness and early warning of anomalies. Data analytics and AI algorithms can further support predictive maintenance by identifying fault trends and optimizing intervention timing. Preventive testing, such as insulation resistance measurement, dielectric loss (tanδ) testing, and partial discharge detection, should be conducted regularly to uncover hidden defects. External inspections are equally important, focusing on loose terminals, oil leakage, corroded supports, and surface contamination. Regular cleaning with appropriate tools and agents helps maintain heat dissipation and insulation performance.

In harsh environments—such as high humidity, extreme temperatures, or heavily polluted areas—additional protective measures are necessary. These may include installing protective enclosures, improving ventilation, and performing regular dehumidification and cleaning to mitigate environmental degradation. Continuous monitoring of operating parameters and environmental conditions enables a comprehensive assessment of equipment health.

When a fault occurs, accurate diagnosis is the first step. A combination of operational data, visual inspection, and electrical testing should be used to determine the fault type and location. Common response measures include isolation, repair, or replacement. Once a fault is detected, the capacitor should be promptly disconnected to prevent further damage. Repairable issues—such as replacing aged seals or fixing localized insulation damage—must be handled according to technical standards. If the damage is severe, the unit should be replaced with a new one matching the required specifications. After replacement or repair, tests such as capacitance measurement and withstand voltage testing must be performed to verify performance before re-energization.

Equally important is the establishment of a robust fault recording and analysis system. Detailed records of fault type, cause, handling procedure, and environmental conditions should be maintained. Statistical analysis of these records helps identify recurring issues and underlying risk factors. Long-term tracking of repaired or replaced units ensures their performance remains stable. Over time, this data-driven approach supports continuous improvement in design, manufacturing, and maintenance practices, shifting from reactive to proactive management.

In conclusion, as a key component for reactive power compensation, the reliable operation of power capacitors depends on sound design, strict manufacturing quality, and systematic operation and maintenance. By integrating smart monitoring, preventive testing, environmental adaptation, and closed-loop fault management, their service life can be extended, failure rates reduced, and overall system reliability enhanced. Strengthening technical management and maintenance systems will provide strong support for the safe, efficient, and sustainable development of power grids.