What Are the Common Faults of 10kV Switchgear?

10kV switchgear is a key equipment in power distribution systems, widely used in substations, factories, commercial buildings, and other places. However, in long-term operation, the failure rate of switchgear is relatively high, ranging from affecting power supply reliability to potentially causing arc short circuits, explosions, and even endangering personal safety.

This article will provide a detailed analysis of common fault types, causes, practical testing methods, and handling measures for 10kV switchgear, helping operation and maintenance personnel to master the maintenance and fault handling experience of switchgear.

Ⅰ.Common fault types of 10kV switchgear

The main faults of 10kV switchgear can be divided into four types: electrical faults, mechanical faults, insulation faults, and control circuit faults:

Ⅱ Analysis of Common Electrical Faults in 10kV Switchgear

1. Circuit Breaker Refusal or Misoperation

Fault phenomenon: The circuit breaker cannot be closed or opened, which may result in overcurrent or short circuit situations but still fail to operate, leading to equipment damage.

Common reasons:

• Energy storage mechanism malfunction: The closing of the energy storage is not completed, and the opening and closing operations cannot be performed.
• Burning of closing/opening coil: Due to unstable voltage or long-term electrification, the coil overheats and burns out.
• Poor contact of auxiliary switch: circuit breaker not fully closed or mechanism stuck.
• Secondary circuit failure: Control power supply disconnected, loose terminals, relay contact failure.

Handling methods:

• Check if the energy storage motor is working properly, and if necessary, manually store the energy and test the closing.
• Measure the resistance value of the closing/opening coil with a multimeter to determine if it is damaged.
• Check the control circuit terminal block to ensure that the cables are not loose or oxidized.
• Verify whether the secondary circuit is normal through a relay protection tester.

2. High voltage fuse burned out

Fault phenomenon: During the operation of the switchgear, the fuse suddenly burns out, causing a power outage on the busbar or load side.

Common reasons:

• Short circuit of the circuit or equipment leads to overload and melting of the fuse.
• Internal faults in the switchgear, such as loose busbars and short circuits in high-voltage cables.
• The protection setting value is too low, causing the fuse to burn out due to misoperation.
• Grounding fault in the circuit leads to abnormal increase in current.

Handling methods:

• Measure the voltage at both ends of the fuse to determine if it is caused by a short circuit.
• Thoroughly inspect the busbar joints, cable heads, and equipment connection points to prevent looseness.
• Infrared thermometer detects the heating condition of fuses and identifies potential hazards in advance.
• Adjust the setting value of relay protection to avoid misoperation.

3. Busbar discharge and insulator damage

Fault phenomenon: There is a "crackling" discharge sound or a burnt smell inside the switchgear, and there are flashing marks on the surface of the insulator.

Common reasons:

• Loose busbar joints result in arc discharge.
• Insulators are affected by moisture and surface dust, which reduces the insulation level.
• The high humidity in the environment leads to condensation and discharge.
• After years of operation, the coating of the busbar has aged and the voltage resistance has decreased.

Handling methods:

• Use an infrared thermometer to check the temperature of the busbar joint, and promptly tighten the bolts if any hot spots are found.
• Clean the dust on the surface of the insulator and improve its insulation capacity.
• When the humidity in the substation is high, install dehumidification devices to prevent condensation from causing discharge.
• Use power frequency withstand voltage test to check the insulation level of the busbar.

 Ⅲ. Mechanical Fault Analysis of 10kV Switchgear

1. The isolation switch cannot be pulled and is stuck

Fault phenomenon: When operating the isolation switch, it cannot be opened or closed smoothly, and the manual operation force is too strong.

Common reasons:

• The mechanical connecting rod is rusted and poorly lubricated.
• The internal spring of the institution is deformed or stuck.
• The auxiliary switch of the secondary circuit has not been reset, resulting in the inability to operate.

Handling methods:

• Check the linkage mechanism and lubricate the moving parts after power failure.
• Replace the spring and adjust the limit mechanism to ensure smooth operation.
• Manually reset the auxiliary switch to ensure it does not affect operation.

2. Failure of operating mechanism spring

Fault phenomenon: The operating handle of the circuit breaker is loose, and it cannot maintain the locked state after closing.

Common reasons:

• The spring is fatigued and aged, and cannot provide sufficient locking force.
• The mechanism is stuck, causing the energy storage mechanism to not be fully released.

Handling methods:

• Replace the faulty spring and apply lubricating grease.
• Manually test the energy storage mechanism after power failure to ensure smooth operation.

Ⅳ. Relay protection misoperation

Fault phenomenon: The load current is normal, the switchgear suddenly trips, and the secondary circuit protection signal is abnormal.

Common reasons:

The protection setting value is incorrect, resulting in misoperation.

The CT circuit of the current transformer is disconnected, resulting in incorrect protection judgment.

The unstable voltage of the control power supply affects the operation of the relay.

Handling methods:

Verify the setting value through a relay protection tester.

Use a multimeter to check if the CT secondary circuit is disconnected.

Ensure the stability of the control power supply and check the battery or UPS power supply status.

Ⅴ.Operation and maintenance management of 10kV switchgear

In order to ensure the long-term stable operation of the 10kV switchgear, maintenance personnel should take preventive maintenance measures:

• Regular infrared temperature measurement to identify potential heat hazards.
• Partial discharge detection can detect insulation aging issues in advance.
• Mechanical mechanism maintenance, lubrication of moving parts to prevent jamming.
• Cable joint inspection to prevent looseness, oxidation, and reduce the risk of arc discharge.
• Regularly clean dust and moisture to improve insulation performance.

Ⅵ. Conclusion

10kV switchgear faults are concentrated in four major types: electrical, mechanical, insulation, and secondary circuits. Circuit breaker refusal to operate, internal discharge, mechanism jamming, and protection abnormalities are high-frequency pain points in operation and maintenance. Most accidents are caused by moisture accumulation, loose joints, aging components, and secondary circuit defects. To avoid the risk of arc explosion and ensure reliable power supply and personal safety, it is necessary to carry out pre control work such as infrared temperature measurement, partial discharge detection, institutional maintenance, dust removal and dehumidification, and protection verification, in order to detect and dispose of hidden dangers early.

If you want to obtain more information related to the operation and maintenance, fault diagnosis, and preventive testing of 10kV high-voltage switchgear, please continue to contact us.