Reasons for overhead cable measurement failure

The stranded resistance failure phenomenon occurs because all the resistance measurements failed to uniformly measure the current flowing through the specimen.

For all single wire overhead cable core reliably and current lead-in phase, and the line between the insulating core of the monofilament along the filament current flow into a spiral. So in the same filament diameter, homogeneous case, the sample perpendicular to the section line should be the core and other planes, in between the filaments of the section the potential difference is zero. In the allelic case, the potential difference between the voltage at the terminal will not shape the voltage clamp, the way contact with the sample surface changes and changes the pressing force of the sample.

Currently stranded resistance measuring jig shape much like a knife-shaped and bounded by tightening the bolts on the sample to generate pressure. Due to the presence of aluminum monofilament surface oxide film, when measuring the current through the introduction of a sample of this form jig, its current distribution is often uneven, stranding the outer filaments' current density. This phenomenon increases with the cross-section stranded seriously. The V-type current clamp is less than knife-like, and the annular current folder has a greater improvement but does not allow the current to achieve the desired homogeneous state. 

Uneven distribution measuring current to voltage terminal 1m apart two of the voltage difference is greater than the current uniform measuring the voltage difference between two voltage terminal. In this case, the shape of the voltage terminal clamps, and pressure for closer improvements are often not effective. Therefore, the key to solving the problem is how to measure the resistance by measuring current and voltage terminal clamps' uniform requirements, which can measure the current uniform from the sky.