Insulation aging is an inevitable process that leads to reduced reliability and eventual failure of electrical assets .
According to the IEC definition, an aging factor is any external stress that causes this degradation .
For medium-voltage equipment, the main factors can be categorized into four key areas: electrical, thermal, environmental, and mechanical.
Here is a detailed breakdown of the causes:
1. Electrical Stress (Partial Discharge)
Electrical aging is primarily caused by Partial Discharge (PD) . These are small, localized electrical discharges that erode the insulation over time.
Surface Erosion: High-intensity discharges create heat, ozone, and charged particles that physically erode the material surface, creating micro-voids that further weaken the insulation until failure .
Tracking: Under wet and contaminated conditions, leakage current can dry the surface, creating a conductive carbon path (tracking) which can lead to a flashover .
2. Thermal Stress (Overheating)
Heat is a dominant aging factor. Every 10°C increase in temperature can halve the insulation's lifespan (a principle known as the 10°C rule).
Overloading: Operating equipment beyond its rated current generates excess heat, accelerating the chemical breakdown of the insulating material.
Poor Connections: Loose or oxidized connections cause localized hotspots that rapidly degrade nearby insulation.
3. Environmental Conditions
Exposure to the external environment significantly accelerates aging .
UV Radiation: Sunlight causes photo-degradation of polymer materials, leading to chalking, cracking, and loss of hydrophobicity (water repellency). This creates an erosion path for electrical discharges .
Moisture & Humidity: Water ingress reduces insulation resistance and can cause hydrolysis (chemical breakdown of polymers). In coastal areas, salt accumulation on surfaces increases conductivity, leading to higher leakage currents and flashover risks .
Pollution & Contaminants: Chemical pollutants (industrial fumes, acid rain) and salt are highly corrosive. Studies show pollution can significantly increase the rate of insulation degradation .
4. Mechanical Stress
Physical forces can compromise insulation integrity.
Vibration & Cycling: Constant vibration from conductors or thermal expansion/contraction can cause material fatigue, cracking, and delamination at interfaces between different materials (e.g., between the core and housing of a composite insulator) .
Fiber Breakage: In composite insulators, corrosion of the fiberglass rod can cause "decay-like fracture," where the glass fibers break and the rod weakens structurally, often before electrical failure .
Practical Summary
In daily operations, aging never has a single cause; these factors work together to worsen the effects synergistically. For example, a contaminated insulator becomes a path for leakage current, which generates heat (thermal factor), accelerating the formation of tracking and eventual flashover .
Regular maintenance, cleaning, and thermographic inspections are effective methods to detect early signs of these aging factors before they lead to costly equipment failure
Products Description
24kV contact box is an insulating component molded by epoxy resin APG pressure gel molding process. It is mainly used in trolley-type switchgear and undertakes the functions of electrical connection and insulation isolation.
Our address
No. 1 East Gaoxin Avenue in the High-Tech Development Zone of Baoji City, Shaanxi Province, China
Phone Number
+86 180 9176 5658
xdtz03@westpowerelectric.com
