Analysis Of The Causes Of Frequent Porcelain Insulator Fractures In 220kv High-voltage Disconnect Switches

In power systems, 220kV voltage level equipment is widely distributed, and its operational stability directly affects grid security. Analysis of extensive maintenance data reveals that the fracture of post insulators (porcelain insulators) in High Voltage Disconnect Switch equipment is particularly prominent in 220kV systems. This phenomenon is not accidental but rather caused by a combination of factors, including the equipment's mechanical structure, material properties, and external load environment.

Structural Stress Concentration and Bending Load Influence

220kV equipment typically employs multi-section porcelain insulator posts, significantly increasing its overall height. Compared to lower voltage levels, the posts bear a greater lever torque during operation. During the opening and closing of high-voltage disconnect switches, severe stress concentration occurs at the flange root of the insulator due to the shift in the center of gravity and the impact load from the mechanism's movement.

• Lever Arm Effect: The taller the porcelain post, the greater the bending moment generated on the base by the conductor tension or wind deflection force at the top.

• Glue Bonding Process: If the cement adhesive layer between the flange and the porcelain component lacks flexible buffering, thermal expansion and contraction caused by temperature changes can prevent the release of internal stress.

The Relationship Between Material Brittleness and Manufacturing Defects

Porcelain components, as a typical brittle material, are extremely sensitive to internal defects. Some operating high-voltage disconnecting switches use quartz porcelain, which has low bending strength.

Performance Differences Between Silica and Alumina Porcelain

Research shows that early-operated porcelain insulators had an Al₂O₃ content of less than 30%, resulting in insufficient mechanical toughness.

• Internal Stress: Improper control of the firing process during production can leave micro-cracks inside the porcelain components.

• Degradation Rate: Under long-term strong electric field and mechanical force coupling, the crack propagation rate of quartz porcelain is much higher than that of alumina porcelain.

The Combined Effect of Operating Environment and Installation Deviations

The installation method of tubular busbars has a decisive impact on the insulator life. If the compensating regulator fails, the axial thrust generated by the thermal expansion and contraction of the busbar will directly act on the supports of the high-voltage disconnecting switch.

Severe weather conditions such as strong winds, earthquakes, or icing can induce high-frequency, low-amplitude vibrations. This fatigue load is a key factor that causes latent cracks in 220kV porcelain insulators to evolve into sudden fractures. Supports subjected to this high dynamic stress over a long period will gradually fatigue the porcelain at the flange edges, eventually leading to complete failure during a certain operation.