What failure modes occur in cable fittings under high temperature or humid conditions?

Cable Fittings Failure Modes under High Temperature or Humid Conditions

1. Insulation Aging and Corrosion:

High temperatures accelerate the thermal oxidation of insulation materials, while humidity promotes moisture penetration into the metal surface, triggering electrochemical corrosion, leading to insulation peeling or metal component corrosion.

2. Water Intrusion Leading to Discharge (Flashover):

In humid environments, water droplets form a continuous water film in the air gap of the joint. Under the influence of the electric field, partial discharge occurs, forming flashover traces that gradually expand and eventually evolve into permanent failures.

3. Stress Relaxation and Air Gap Formation Caused by Thermal Stress:

High temperatures cause a mismatch in the thermal expansion coefficients of metals and polymers, resulting in internal stress relaxation. Tiny air gaps appear between the joint and the cable, further exacerbating moisture penetration and insulation failure.

4. Material Softening and Decreased Mechanical Strength:

Under sustained high temperatures, the mechanical strength of non-metallic materials such as nylon and polyester decreases, causing clamps and fixtures to loosen, increasing the risk of cracks or fractures caused by vibration and impact.