Analysis Of Bolted Tension Clamp Failure: Direct Cause Of Conductor Breakage
Why does the failure of bolt-type tension clamps lead to conductor breakage?
In the operation and maintenance of power transmission lines, there is a direct causal relationship between bolted type strain clamp failure and conductor breakage. When dead end strain clamp fails, it often triggers a chain reaction at the weakest anchor point of the conductor, eventually leading to a wire breakage accident.
Contact Failure: The Evolution from Heating to Burnout
Bolt-type tension clamps rely on bolt pressure to fix the conductor. If the installation torque is insufficient or vibration during operation loosens the clamp, it will lead to increased contact resistance. Poor contact will cause continuous heating, resulting in oxidation and corrosion. As the temperature rises, the contact surface between the clamp and the conductor oxidizes more rapidly, further increasing the resistance and creating a vicious cycle. When the temperature exceeds a critical value, the clamp locally overheats and softens, eventually causing the conductor to burn out or break under tension. Gaps caused by inadequate tightening of the drain plate can lead to arcing under wind or current, directly melting the conductor.
Hidden Risks of Crimping and Corrosion
Besides heating during operation, initial construction defects are also a significant contributing factor.
-
Hidden dangers in crimping process: Some bolted dead end clamp wires suffer from broken strands or damaged galvanized layers during installation. These hidden damages easily lead to electrochemical corrosion in humid environments.
-
Exacerbated corrosion environment: The report "Analysis of the Failure Process and Causes of Tension Wires" mentions that after acidic rainwater seeps into the clamp, corrosion products accumulate, causing a sharp decrease in clamp gripping force. The steel core's diameter decreases due to corrosion, eventually leading to breakage under normal operating tension.
Loss of mechanical properties and conductor breakage:
When bolt-type tension clamps loosen due to vibration or impact, their gripping force will be less than 90% of the conductor's rated breaking force. At this time, the conductor experiences abnormal stress concentration at the clamp outlet. Combined with fatigue caused by light wind vibration, it may pull out of the clamp or break strands, ultimately leading to wire breakage. The GB50233-2014 standard also emphasizes that its gripping strength test must be qualified; otherwise, it can easily create operational hazards.
