The Quality Of Fasteners Affects The Connection Status Of Parallel Groove Clamps.
It is generally believed in the industry that once the fastener quality meets the standards, connector parallel groove can maintain a stable connection. However, this assessment requires further technical verification in actual engineering projects.
The bolt-type groove clamp uses the tightening pressure of the bolt to fix the wire, while the flat washer and spring washer play the role of transmitting pressure. When the fastener material conforms to the national standards GB2314 and DL/T 765.1, parallel groove can provide a gripping force of 10%-20% of the calculated breaking force for the conductor. This value seems sufficient for non-load-bearing connections, but long-term operating conditions are far more complex than theoretical conditions.
Actual operation data of the power distribution network shows that, generally speaking, after 3-5 years of operation, some connection points of the parallel groove clamp connector may experience increased contact resistance. Repeated conductor creep and thermal expansion and contraction act on the contact interface, gradually diminishing the compensating ability of ordinary elastic washers. In temperature cycling tests, even if the fastener material is qualified, the regeneration of the oxide layer on the contact surface will still affect conductivity. The active oxide layer at the aluminum-aluminum interface may reform after pressure changes, reducing the effectiveness of the initially applied conductive grease.
Vibration loads in the operating environment of power lines are also significant. Wind-induced swaying and short-circuit electrodynamic forces will exert periodic stress on the pg clamp connector, and traditional flat pad combinations are difficult to offset the preload loss caused by such dynamic loads. Some lines therefore use two or three pg clamps equidistant parallel connections to disperse the risk, which precisely illustrates that the long-term reliability of a single connection point is uncertain.
