What are the common faults of box-type substations?

The common faults of box-type substations can be divided into the following categories, involving reasons 

such as equipment aging, environmental influences, and improper maintenance:

### I. Faults of the High-voltage Power Distribution Unit

1. **Oxidation or Poor Contact of the Contacts**

   - Cause: The surface of the contacts is oxidized due to long-term operation, or the contact pressure is insufficient

 during installation.

   - Consequence: Local heating, insulation breakdown, and even short-circuit faults may occur.

2. **Failure of the Lightning Arrester**

   - Cause: The lightning arrester is aging, or the overvoltage caused by lightning strikes exceeds its protection range.

   - Consequence: The equipment may be impacted by overvoltage, damaging the internal components.

3. **Measurement Error of the Transformer**

   - Cause: The transformer is aging, or the wiring of the secondary circuit is loose.

   - Consequence: The monitoring data is inaccurate, affecting the reliability of the relay protection action.

### II. Transformer Faults

1. **Oil Leakage of the Oil-immersed Transformer**

   - Cause: The sealing ring is aging, there are cracks at the welding points, or the interface of the radiator is loose.

   - Consequence: The decrease in the oil level leads to a reduction in insulation performance, and even a fire

 may be caused.

2. **Short-circuit of the Transformer Winding**

   - Cause: Insulation aging, intrusion of foreign objects, or breakdown due to overvoltage.

   - Consequence: The transformer is burned out, causing a power outage accident.

3. **Failure of the Temperature Control System**

   - Cause: The oil temperature gauge fails, or the fan control module malfunctions.

   - Consequence: Insufficient heat dissipation leads to overheating of the transformer, shortening its service life.

### III. Faults of the Low-voltage Power Distribution Unit

1. **Frequent Tripping of the Main Circuit Breaker**

   - Cause: Overload, short circuit, or unreasonable setting of the circuit breaker's setting value.

   - Consequence: It affects the stability of power supply, and it is necessary to check the load or replace the

 equipment.

2. **Failure of the Reactive Power Compensation Device**

   - Cause: The capacitor is aging, the fuse is blown, or the controller malfunctions.

   - Consequence: The power factor decreases, increasing the line loss.

3. **Overheating of the Busbar**

   - Cause: The busbar connection is loose, or the current is overloaded.

   - Consequence: The insulation material melts, and even a fire may be caused.

### IV. Faults of the Shell and Structure

1. **Poor Sealing of the Enclosure**

   - Cause: The sealing strip is aging, the enclosure is deformed, or the drain hole is blocked.

   - Consequence: Rainwater and dust invade, leading to a decrease in the insulation of the equipment.

2. **Corrosion Problem**

   - Cause: Insufficient anti-corrosion treatment of the enclosure material, or long-term exposure to a

 corrosive environment.

   - Consequence: The structure of the enclosure is damaged, and the internal equipment gets damp

and rusty.

### V. Faults of the Auxiliary Equipment

1. **Malfunction of the Intelligent Monitoring System**

   - Cause: The communication module fails, the sensor is damaged, or there is a software misoperation.

   - Consequence: It is impossible to remotely monitor the equipment status, delaying the fault handling.

2. **Fault of the Cable Terminal**

   - Cause: The cable insulation is aging, the joint is loose, or there are construction quality problems.

   - Consequence: Local discharge, heating, and even inter-phase short circuit may occur.

### VI. Environment-related Faults

1. **Influence of Extreme Temperatures**

   - High-temperature environment: Poor heat dissipation leads to a shortened service life of the 

equipment.

   - Low-temperature environment: The viscosity of the oil in the oil-immersed transformer increases, 

affecting the insulation performance.

2. **Intrusion of Small Animals**

   - Cause: The gaps in the enclosure are not sealed, and small animals (such as mice) enter and bite 

the wires.

   - Consequence: It causes short-circuit or grounding faults.

### Fault Prevention and Maintenance Suggestions

1. **Regular Inspections**: Check the appearance, temperature rise, peculiar smell, and sound of the 

equipment, and clean the internal dust.

2. **Preventive Tests**: Test the insulation resistance, contact resistance, and the action characteristics 

of the relay protection.

3. **Environmental Management**: Ensure good sealing of the enclosure, clean up the surrounding 

debris, and avoid water accumulation.

4. **Intelligent Upgrades**: Install an online monitoring system to provide real-time early warnings 

of potential faults.

Through targeted maintenance and optimized design, the failure rate of box-type substations can be 

significantly reduced, ensuring the stable operation of the power distribution system.