What are the common faults in high and low voltage switchgear?

As the core control equipment of the power system, common faults of high and low voltage switchgear 

can be divided into the following six categories. The following are the specific analysis and corresponding

 suggestions:

### I. Mechanical Faults

1. **Poor Contact of Contacts**

   - **Manifestation**: Oxidation, ablation of contacts or insufficient spring pressure leads to an increase in

 contact resistance, causing local heating (which can be detected by infrared temperature measurement).

   - **Consequences**: In severe cases, the contacts will be welded, triggering inter-phase short circuits or

 equipment burnout.

   - **Treatment**: Regularly clean the contacts, replace the ablated components, and adjust the spring 

pressure to the manufacturer's standard value.

2. **Blocking of the Operating Mechanism**

   - **Reasons**: Insufficient lubrication of mechanical components, foreign objects getting stuck in, or 

deformation of the transmission mechanism.

   - **Consequences**: The circuit breaker cannot open and close normally, leading to the expansion of the fault.

   - **Maintenance**: Lubricate and maintain the operating mechanism every year, and check the wear of 

the transmission components.

### II. Electrical Faults

1. **Overload and Short Circuit**

   - **Inducing Factors**: The loop load exceeds the rated current or insulation breakdown causes a 

short circuit.

   - **Characteristics**: The protection device trips, and the cables or busbars heat up and emit smoke.

   - **Prevention**: Install smart electricity meters to monitor the current in real time, and configure 

appropriate overload protection devices.

2. **Insulation Aging and Failure**

   - **Environmental Factors**: Being in a high-temperature, humid or corrosive environment for a long time.

   - **Detection Method**: Measure with an insulation resistance meter. If the resistance value is lower than

 0.5MΩ, the insulation parts need to be replaced.

   - **Countermeasures**: Install a moisture-proof heater, and regularly replace the aged insulators and cables.

### III. Faults of Protection Devices

1. **False Operation or Refusal to Operate**

   - **Reasons**: Incorrect setting of relay protection values, distortion of transformer signals, or aging 

of device components.

   - **Case**: In 2023, a substation had frequent false trips due to a too small zero-sequence protection

 value, resulting in a regional power outage.

   - **Solution**: Calibrate the protection device every year, and use a relay protection tester to simulate 

fault conditions for testing.

2. **Insufficient Breaking Capacity of the Circuit Breaker**

   - **Risk**: When the short-circuit current exceeds the rated breaking capacity of the circuit breaker, 

an explosion may occur.

   - **Suggestion**: Select the circuit breaker according to the system short-circuit capacity, and upgrade 

the old equipment to a high-breaking capacity model.

### IV. Environment-related Faults

1. **Condensation and Dampness**

   - **Harm**: It leads to a decrease in insulation and corrosion of metal components.

   - **Treatment**: Install a temperature and humidity controller to link with a dehumidifier, and seal the 

cable inlets and outlets with fireproof putty.

2. **Invasion of Dust and Foreign Objects**

   - **Typical Scenario**: In the switchgear in an industrial area, creepage occurs due to dust accumulation.

   - **Measures**: Use compressed air to blow the dust inside the cabinet every quarter, and install

 dust-proof filters.

### V. Improper Installation and Maintenance

1. **Loose Wiring**

   - **Inspection Method**: Use a torque wrench to confirm the tightening force of the bolts (for example,

 the M10 bolt needs to reach 40N·m).

   - **Consequences**: An increase in contact resistance leads to heating. In 2024, a fire occurred in an 

enterprise due to loose busbar bolts.

2. **Defects in Cable Terminal Making**

   - **Common Problems**: Irregular insulation wrapping of the cable terminal head leads to local discharge.

   - **Standard**: Adopt cold shrinkage or heat shrinkage processes to ensure a smooth transition between

 the semi-conductive layer and the insulation layer.

### VI. Other Faults

1. **Abnormalities of Meters and Indicator Lights**

   - **Troubleshooting**: Check whether the secondary circuit of the voltage transformer is open-circuited, 

and whether the indicator lights are burned out.

   - **Alternative Solution**: Install a multi-functional power meter to monitor the three-phase voltage and

 current in real time.

2. **Electromagnetic Interference**

   - **Phenomenon**: The control circuit is mis-triggered, and the microcomputer protection device 

gives false alarms.

   - **Countermeasures**: Use shielded twisted-pair cables for control cables, and the grounding resistance 

should be less than 4Ω.

**Suggestions for Prevention and Management**:

1. **Regular Patrol Inspection**: Conduct infrared temperature measurement every month, and carry out a

 withstand voltage test every six months.

2. **Status Monitoring**: Install partial discharge sensors and an online temperature monitoring system.

3. **Personnel Training**: Ensure that the operators are familiar with the equipment characteristics and 

emergency response plans.

4. **Spare Parts Management**: Stock common vulnerable parts such as contacts and coils to shorten the 

fault recovery time.

Through the above classified management, the failure rate of the switchgear can be effectively reduced, 

and the safe and stable operation of the power system can be ensured.