10kV RMU Common Faults & Solutions Guide

1.Application Issues and Handling Measures for 10kV Ring Main Units (RMUs)

The 10kV ring main unit (RMU) is a core power distribution device in urban 10kV distribution networks, widely used in industrial parks, residential communities, commercial centers, and public facilities for medium-voltage power supply and flexible power distribution. Its primary function is to enable flexible energy distribution, ring-fed operation, and fault isolation at the 10kV voltage level. However, during long-term operation, 10kV RMUs may encounter various issues caused by electrical, mechanical, or environmental factors, potentially affecting power supply reliability. Below are common operational problems and their corresponding corrective measures.

2. Electrical Faults in 10kV Ring Main Units

2.1 Internal Short Circuit or Poor Wiring
Loose cable terminations, damaged insulation, or poorly connected busbars inside a 10kV RMU can lead to phase-to-phase or ground faults, resulting in abnormal heating, protective tripping, or even equipment explosion.
Measure: Conduct regular de-energized inspections of the internal components, focusing on cable terminations, busbar joints, and switch contacts. Tighten or replace any loose or scorched connections, and ensure all wiring is secure and properly insulated.

2.2 External Short Circuit Faults
A short circuit downstream of the 10kV RMU—such as cable breakdown or insulation aging in connected equipment—may cause fuse blowing or circuit breaker tripping, interrupting power supply.
Measure: Quickly locate the fault point along the 10kV feeder, repair insulation defects, or replace damaged components. Replace fuses with correct specifications, or reset and test the tripped breaker before restoring power.

2.3 Leakage Current or Ground Faults
In humid, polluted, or aging environments, insulating components (e.g., bushings, insulators) within the 10kV RMU may become damp or contaminated, leading to partial discharge or single-phase-to-ground faults. This creates leakage current, posing risks of fire or electric shock.
Measure: Immediately de-energize the unit and use an insulation resistance tester to identify the ground fault. Clean contaminated insulation surfaces, replace degraded components, and install ground fault monitoring systems to enhance early warning capabilities in 10kV networks.

3. Mechanical and Auxiliary Device Issues

3.1 Inflexible Operation of Components
Load switches, circuit breakers, or earthing switches in a 10kV RMU may become stiff or fail to operate properly due to lack of use or insufficient lubrication, compromising safe switching operations.
Measure: Establish a regular operation and maintenance schedule. Clean and lubricate transmission mechanisms and spring-operated components. For motorized actuators, verify the motor and control circuit functionality.

3.2 Failure of Auxiliary Devices
Voltage transformers (VTs) and current transformers (CTs) installed in 10kV RMUs may develop secondary open circuits, inter-turn short circuits, or insulation degradation, leading to inaccurate metering, false protection tripping, or data anomalies in monitoring systems.
Measure: Regularly calibrate the ratio and polarity of VTs and CTs. Replace faulty units promptly after shutdown. Never leave a CT secondary circuit open—ensure all connections are secure after maintenance.

4. Environmental and Operational Challenges

4.1 Excessive Temperature
Under high-load conditions, poor ventilation or inadequate heat dissipation in a 10kV RMU can cause internal temperatures to exceed allowable limits (typically ≤65°C), accelerating insulation aging and reducing equipment lifespan.
Measure: Ensure the RMU is installed in a well-ventilated location. Install online temperature monitoring devices. When necessary, reduce the 10kV load or add forced cooling fans.

4.2 Humidity and Condensation
In southern regions or areas with high rainfall, moisture ingress due to inadequate sealing can cause condensation inside the 10kV RMU, significantly reducing air insulation strength and increasing the risk of flashover.
Measure: Use RMUs with IP54 or higher protection rating. Install anti-condensation heaters or desiccants inside the cabinet. Regularly inspect and replace aging door seals.

5.Conclusion

As a critical node in urban power distribution networks, the reliable operation of 10kV ring main units directly impacts the continuity and safety of regional power supply. To ensure long-term stability of 10kV RMUs, a proactive "preventive maintenance and timely intervention" strategy must be adopted:

• Implement regular inspection and maintenance routines, with special attention to 10kV cable connections, insulation condition, operating mechanisms, and ambient temperature/humidity;

• Train operation personnel in proper 10kV equipment handling and emergency response procedures;

• Promote intelligent monitoring technologies—such as partial discharge detection and wireless temperature sensors—for early fault warning;

• Strictly follow safety operation protocols to prevent human errors.

Only through scientific management, standardized operation, and proactive maintenance can the operational reliability of 10kV ring main units be comprehensively enhanced, providing a solid foundation for safe, efficient, and resilient urban power distribution systems.