What are the selection methods and maintenance precautions for high-voltage switchgear?

High-voltage switchgear is a critical piece of equipment in power systems, and its selection and maintenance directly affect the reliability, safety, and economy of power supply. The following will systematically explain the selection methods and maintenance considerations.

Selection Method for High-Voltage Switchgear

Selecting high-voltage switchgear is a systematic project that requires comprehensive consideration of factors such as technical parameters, operating environment, standards, and cost. The following are the core selection steps and key points:

1. Determine Basic Technical Parameters
This is the foundation of selection and must be compatible with the power grid system.

Rated Voltage: Must be greater than or equal to the system's nominal voltage (e.g., 10kV, 35kV).

Rated Current: The maximum long-term operating current calculated based on the load, with a certain margin (usually 1.2-1.5 times).

Rated Short-Circuit Breaking Current: The maximum short-circuit current that the circuit breaker in the switchgear can safely interrupt; should be greater than or equal to the expected short-circuit current at the installation location.

Rated Short-Time Withstand Current: The thermal and dynamic stability capabilities that the switchgear can withstand under short-circuit current, which must also meet system requirements.

Protection Rating: Such as IP4X (protection against solid foreign objects larger than 1mm in diameter), the internal compartments must reach IP2X or higher to ensure personal safety.

 

2. Determine the Main Wiring Scheme and Model

Main Wiring: Based on power supply reliability requirements, determine whether it is a single busbar, a segmented single busbar, or a double busbar, etc.

Cabinet Type Selection:

Fixed: Such as the XGN series, lower cost, but inconvenient maintenance and relatively lower safety.

Removable (Cart-type): Such as the KYN series, the mainstream choice. The circuit breaker can be pulled out of the cabinet, high safety, convenient maintenance, and easy to quickly restore power supply.

Ring Main Unit: Such as the HXGN series, used for ring network power supply or end users, commonly using a load switch

 

3. Core Component Selection

Circuit Breakers: Vacuum circuit breakers (mainstream, environmentally friendly, low maintenance) or SF6 circuit breakers. Pay attention to their mechanism (spring-operated mechanisms are most common), lifespan, and mechanical and electrical characteristics.

Instrument Transformers: The accuracy and transformation ratio of current transformers and voltage transformers must meet measurement and protection requirements.

Comprehensive Protection Devices: The core of modern intelligent switchgear, requiring comprehensive protection (instantaneous trip, overcurrent, grounding, etc.), measurement, communication, and fault recording functions.

Grounding Switches: Ensure maintenance safety; require reliable mechanical or electrical interlocking with the circuit breakers.

Surge Arresters/Overvoltage Protectors: Protect equipment from damage caused by lightning or operational overvoltages.

 

4. Environmental Considerations and Special Requirements

Environmental Conditions: Altitude (affects insulation), ambient temperature, humidity, pollution level (determines external insulation creepage distance), seismic intensity.

Intelligent Requirements: Whether online monitoring functions (such as temperature, mechanical characteristics, partial discharge monitoring), remote control, and status diagnostics are required.

Five-fold interlocking: This must be met! It prevents accidental opening and closing of circuit breakers, prevents opening and closing of disconnecting switches under load, prevents connecting grounding wires while energized, prevents closing of switches with grounding wires connected, and prevents accidental entry into energized compartments. The reliability of the interlocking is of paramount importance.

 

5. Brand, Standards, and Cost

Standards: Complies with Chinese standards such as GB and DL, as well as IEC international standards.

Brands and Qualifications: Choose manufacturers with a good reputation, mature technology, and comprehensive after-sales service. Products should have passed type testing and be certified by an authoritative organization.

Life Cycle Cost: Consider not only the initial purchase cost but also the long-term costs such as installation, operation, maintenance, and power outage losses.

 

Maintenance Precautions for High-Voltage Switchgear

 

The maintenance of high-voltage switchgear should adhere to the principle of "prevention first, safety first" and be strictly carried out in accordance with the "Electric Power Safety Work Regulations".

I. Daily Inspection (Without Power Outage)

Visual Inspection: The cabinet should be free from deformation and rust, and the paint layer should be intact. Observation windows should be clean and undamaged.

Instrument Indications: Check whether the ammeter, voltmeter, wattmeter, and protection device displays are normal.

Signals and Status: Check whether the opening and closing indicators, energy storage indicators, and position indicator lights are correct.

Sound, Light, and Odor: Listen for any abnormal discharge or vibration sounds; smell for any burnt odor; check for any corona discharge or arcing.

Environment and Foundation: Check whether the lighting, ventilation, and dehumidification devices are normal; check for any condensation inside the cabinet; and ensure the cable compartment is dry and clean.

 

II. Regular Maintenance (Power outage required, safety measures implemented)

Safety First Steps: Strictly implement power outage, voltage testing, grounding wire installation, sign hanging, and barrier installation.

1. Mechanical Component Inspection and Maintenance

Interlocking Mechanism: Key inspection! Manual and electric operation to verify 100% reliability of the "five-proof" interlocking function. Check that the mechanical interlocking is flexible and free from jamming.

Operating Mechanism: Inspect the spring energy storage mechanism and the closing and opening mechanism. Clean and lubricate moving parts (using special grease). Check that fasteners are not loose.

Handcart/Disconnecting Switch: Check that the track is level, the pushing and pulling is flexible, and the positioning is accurate. The contact position is correct.

Grounding Device: Check that the grounding switch is fully open and closed, and that the grounding connection is reliable.

2. Electrical Component Inspection and Maintenance

Main Circuit Connections: Check the tightness of all busbars, connectors, and cable joints. This is especially important! Tighten to standard torque using a torque wrench. Check for signs of overheating and oxidation (this can be determined by color change, temperature measurement, or applying a temperature-indicating wax strip).

Primary Insulation Components: Clean the surfaces of insulators, bushings, contact boxes, and wall bushings to remove dirt. Check for cracks, damage, and creepage marks. Measure insulation resistance.

Circuit Breaker Characteristics: Regularly test the mechanical characteristics (such as opening and closing time, speed, and synchronicity) and circuit resistance of the circuit breaker according to the manufacturer's requirements or specifications. This is crucial for assessing the circuit breaker's health status.

Secondary Circuits: Check that terminal block wiring is tight and free of rust. Clean relays and protection devices. Perform functional verification and transmission tests on the protection devices.

3. Special Maintenance Items

Partial Discharge Detection: For important or older switchgear, partial discharge detection methods such as ultrasonic testing and transient ground voltage testing can be performed to promptly detect internal insulation defects.

Infrared Thermometry: Regularly perform infrared thermometry on the cabinet exterior and observation windows to indirectly determine if internal connection points are overheating.

Surge Arrester Inspection: Check the counter's operation and measure leakage current and insulation resistance.

 

III. Application of Intelligent Operation and Maintenance
For intelligent switchgear equipped with a condition monitoring system, its data should be fully utilized:

Analyze the number of circuit breaker trips and cumulative current values ​​to perform predictive maintenance.

Monitor the temperature and humidity inside the cabinet and automatically start and stop the dehumidifier.

Monitor the trend of changes in mechanical characteristics to provide early warning of potential faults.

 

IV. Common Faults and Troubleshooting

Failure to Operate/Misoperation:Often caused by loose secondary circuits, relay malfunctions, jammed mechanisms, or power supply issues.

Insulation Faults:Often caused by condensation, dirt, small animal intrusion, or aging insulation components inside the cabinet.

Overheating Faults:Often caused by loose connections leading to excessive contact resistance.

 

Summary

 

Right selection is the prerequisite: Select components scientifically based on system requirements and strictly control quality.

Maintenance is key: Establish standardized inspection, pre-testing, and maintenance systems, focusing on "five-proof interlocking," connection tightness, mechanical characteristics, and insulation condition.

Safety is the bottom line: All maintenance operations must be carried out with complete safety measures in place.

Technology is the direction: Actively apply intelligent monitoring and diagnostic technologies to achieve the transformation from "periodic maintenance" to "condition-based maintenance."

 

As a benchmark enterprise in Shaanxi's power equipment industry, Shaanxi Huadian adheres to the philosophy that "every cabinet is a safety commitment" and has been deeply involved in the high-voltage electrical field for decades. We employ military-grade manufacturing processes and intelligent production lines to create a full range of switchgear solutions from 10kV to 40.5kV, successfully serving over a thousand key projects in energy, industry, transportation, and municipal sectors. We provide a dual guarantee of "product + service," including lifetime spare parts supply and upgrade services. Please contact us if you are interested.

Email:pannie@hdswitchgear.com.

Whatsapp/Wechat:+8618789455087