The following is a professional analysis of the key points for the core use of epoxy glass cloth insulation pipes, covering key aspects such as selection, construction, and operation and maintenance:
1、 Material selection and pretreatment
1. Principle of compatibility matching
-Select wall thickness based on voltage level (recommended ≥ 3mm for voltages below 10kV), and multi-layer composite structures should be used for high-voltage scenarios.
-Verify the dielectric withstand voltage strength (under normal conditions, it should be>25kV/mm), and special working conditions need to be verified through partial discharge testing.
-The diameter tolerance is controlled within ± 0.5% to ensure a tight fit with the cable/joint.
2. Surface pretreatment standards
-Wipe the surface with anhydrous ethanol before use to remove grease and dust. Do not use solvents containing silicon.
-The cutting end face needs to be polished flat and chamfered (1 × 45 °) to eliminate the electric field concentration caused by burrs.
-Storage environment requirements: temperature 15-35 ℃, relative humidity<60%, avoid direct sunlight that may cause yellowing.
2、 Installation process specifications
1. Key points for operating heat shrink tubing
-Preheating treatment: Use a propane spray gun to evenly heat to 80-120 ℃, avoiding direct contact with open flames.
-Shrinkage control: The longitudinal shrinkage rate shall not exceed 90% of the design value, and there shall be no wrinkles or bubbles in the transverse direction.
-Sealing reinforcement: Wrap a semi conductive tape and self-adhesive tape for dual protection at the overlap, leaving a 2mm gap between layers.
2. Cold wrapping application techniques
-The spiral winding angle is maintained at 45 °, with a coverage rate of ≥ 70% per layer, and the end extends 50mm outside the grounding shielding layer.
-The interface adopts a stepped thinning treatment, and the length of the thickness transition zone is ≥ 2 times the pipe diameter.
-After curing, conduct a power frequency withstand voltage test (dry state): the test voltage is 2U ₀+1kV, and there is no breakdown for 1 minute.
3、 Safety and testing system
1. Electrical Safety Regulations
-Insulation resistance (≥ 1G Ω @ 500V megohmmeter) must be measured before and after installation, and double the assessment in humid environments.
-Regularly conduct infrared thermal imaging detection, and indicate internal defects at temperature difference anomalies.
-Live working is strictly prohibited, and if online maintenance is required, power outage inspection procedures must be carried out.
2. Aging assessment methods
-Microscopic examination: Samples are taken every two years for scanning electron microscopy analysis to observe the interface state of fiberglass/resin.
-Macro judgment: Replace immediately when surface cracks, bubbles, or white color appear.
-Life prediction: According to the Arrhenius model, the design life under normal operating conditions is ≥ 20 years.
The performance of epoxy glass cloth insulation pipes depends on full lifecycle management, from electrical parameter calculation in the selection stage, to environmental control during installation, and to status monitoring during operation. Each link must strictly comply with technical specifications. It is recommended to establish a digital ledger system to record each inspection data and maintenance history, in order to achieve preventive maintenance. For special working condition applications, accelerated aging tests should be conducted in conjunction with material suppliers to develop customized solutions.