Common Faults and Key Maintenance and Repair Technologies for High Voltage Disconnecting Switches

High voltage disconnecting switches are among the most widely used switchgear in power systems. After long-term operation, various faults are prone to occur. Mastering common fault types and maintenance methods is a fundamental skill for ensuring safe power grid operation.

I. Common Fault Types and Cause Analysis

1. Contact Heating

Contact heating is the most common fault of disconnecting switches. Main causes include: contact finger spring aging leading to insufficient contact pressure; surface oxidation or dust accumulation increasing contact resistance; long-term overload operation; poor contact at finger ends causing shunt heating. Severe cases may cause contact melting or even phase-to-phase short circuit accidents.

2. Operating Mechanism Refusal or Jamming

Manifested as incomplete closing or incomplete opening. Causes include: rust or deformation of transmission links; lubricant failure in bearings causing rotation jamming; moisture intrusion into mechanism box causing rusting; insufficient operating power supply voltage, etc.

3. Insulator Damage

Porcelain insulators may develop cracks, glaze peeling, or loosening at flange cementing points; composite insulators may develop shed aging cracking or housing damage. Under severe pollution environments, surface flashover is easily triggered.

4. Conductive Circuit Overheating

In addition to contacts, loose terminal connections, corroded conductor connection plates, etc., can also increase circuit resistance, causing abnormal temperature rise when high current flows, affecting equipment safety.

II. Fault Diagnosis Methods

1. Infrared Thermography Detection

Using infrared thermal imagers to measure the temperature of disconnecting switches in operation can quickly detect abnormal heating at contacts, terminals and other locations. Judgment criteria: when the temperature difference at the same position of similar equipment exceeds the specified value, maintenance should be arranged.

2. Circuit Resistance Testing

During outage maintenance, use a high-current circuit resistance tester to measure the main circuit resistance value. Generally, it should not exceed 1.2 times the manufacturer's specified value. When circuit resistance exceeds the standard, contact condition and conductive connection tightness should be checked.

3. Operating Characteristic Testing

Measure opening/closing time, speed and operating voltage parameters to evaluate the operating mechanism's condition. Also check whether auxiliary switch switching is normal and mechanical interlocks are reliable.

III. Maintenance and Repair Measures

• Regular Cleaning: Remove surface pollution from insulators, clean oxide layers from contacts and conductive contact surfaces
• Lubrication Maintenance: Add lubricating grease to rotating parts and transmission links to prevent rust and jamming
• Tightness Check: Check the tightness of all connecting bolts and terminal connections to prevent loosening and heating
• Rust Prevention and Corrosion Protection: Remove rust and apply anti-corrosion treatment to rusted parts, replace if necessary
• Operating Mechanism Inspection: Test functions of motor, contactor, limit switch and other components of the electric mechanism
• Insulation Testing: Measure insulation resistance during outage to ensure it meets specification requirements

Establishing a management system combining regular inspection and condition-based maintenance is an effective way to reduce the failure rate of disconnecting switches and extend their service life.