The notch test examines the propagation of a nick in the top layer of a wire. Small notches are common during installation or maintenance of wires, and this test evaluates how well the insulation can withstand mechanical stresses after incurring a notch. A pass condition for this test is if, after notching and wrapping, the conductor is not visible. Any indication of exposed conductor is deemed as a failure.
Wire constructions with multiple insulation layers often perform very well in this test as the notch will typically not propagate to the other layers. Single insulation layer constructions, and in particular the extruded single layer constructions, tend to perform the worst in these tests.
Parameters that can be modified for this test:
- Notch tool depth
- Number of wrap cycles
- Use of dielectric voltage withstand test to determine pass/fail criteria