Full analysis of fault diagnosis and prevention strategies for medium and high voltage insulators

2025-07-07 13:47:07

Insulators, as the core components for isolating potential and supporting wires in power systems, have a direct impact on the reliability of the power grid. According to statistics, electrical insulation flashover or breakdown is the leading cause of power outages in transmission lines, with insulator failures being the main reason. This article combines industry standards and engineering practice to systematically analyze the mechanism, diagnostic techniques, and prevention strategies of insulator faults, providing technical guidance for the safe operation of the power grid.   

1、 Typical fault types and mechanisms of insulators

1. Insulation performance failure

-Pollution flashover: Pollutant substances (salt spray, industrial dust) form a conductive layer in a humid environment, causing a significant increase in surface leakage current. When the conductivity of the contaminated layer exceeds the critical value (such as in an E-level polluted area), it may cause flashover. Due to the hydrophobic migration characteristics of silicone rubber, the pollution flashover voltage of composite insulators is significantly higher than that of ceramic/glass insulators.   

-Zero/low value insulator: Ceramic insulators lose their insulation capacity due to manufacturing defects (micro pores, impurities) or long-term mechanical and electrical stress, causing the insulation resistance to drop to near zero. Manual inspection is difficult to detect and requires specialized instruments for testing.   

-Corona discharge: Local electric field distortion ionizes the air, generating ultraviolet pulse signals. Long term corona accelerates the aging of silicone rubber, ultimately leading to flashover.   

2. Mechanical damage

-Post insulator fracture: The main causes include:

-Adhesive stress: The difference in cement expansion coefficient between flange and ceramic parts (12 × 10 ??/K for cast iron vs 4.5 × 10 ??/K for ceramic parts) generates internal stress when there is a large temperature difference;   

-Operation impact: The instantaneous impact force of the isolation switch closing exceeds 300N, and inferior ceramic parts are prone to fracture from the neck;   

-Internal defects: Insufficient ceramic density or slag inclusion, resulting in a decrease of mechanical strength by more than 30%.   

-Composite insulator brittle fracture: Acid liquid enters the core rod through the end sealing gap, corrodes the glass fiber, and ultimately fractures at the wire end fittings.   

3. Environmental adaptability failure

>Data source: National Grid Pollution Flash Statistics

2、 Fault diagnosis technology system

1. Traditional detection methods

-Appearance inspection:

-Ceramic insulator: cracks, glaze peeling (>10mm 2 needs to be replaced)

-Composite insulator: umbrella skirt torn, sheath detached, metal fittings corroded

-Glass insulator: residual hammer retains mechanical strength after self explosion

-Electrical performance testing:

-Insulation resistance test: ≥ 500M Ω (below 35kV) and ≥ 1000M Ω (110kV and above) are qualified (DL/T 626)

-Voltage distribution measurement: If the voltage of a single insulator is 20% lower than the normal value, it is judged as a low value

2. Intelligent diagnostic technology

-Drone image recognition:

-CapsNet optimization algorithm: preserves the angle features of insulators, with a complex background recognition rate of 95%;   

-Multi scale attention mechanism: The accuracy of locating damaged areas reaches 98.7%, reducing the false detection rate by 40% compared to traditional CNN.   

-Vibration signal analysis:

-Gaussian Mixture Model (GMM) extracts spectral features: internal cracks are diagnosed with an accuracy of 92% based on modal bandwidth (σ) and center frequency (μ).   

-UV imaging:

-Corona pulse phase analysis method: Determine corona discharge when the phase difference between positive and negative peak values is 180 °.   

3、 Preventive strategies and engineering practices

1. Selection and environmental adaptation

-Polluted areas:

-Increase creepage distance: For Class IV polluted areas, anti fouling insulators with creepage distance ≥ 31mm/kV should be selected;   

-Spraying RTV coating: improves hydrophobicity, increases pollution flashover voltage by 2-3 times.   

-Ice covered areas:

-Structural optimization: The suspension string adopts a "3+1" large diameter umbrella skirt layout to block the ice bridge passage;   

-Slant hanging method: V-shaped arrangement increases ice flash voltage by 30%.   

2. Operation and maintenance strategy

-Periodic detection:

-Measures to prevent bird damage:

-Installation of anti bird spines: coverage radius ≥ 0.8m;

-Draw a bird pest distribution map and install ultrasonic bird repellers in key areas.   

3. Whole life cycle management

-Quality control at the manufacturing end:

-Ceramic insulator: 100% full coverage by ultrasonic testing (cracks ≤ 1cm are considered defective);   

-Composite insulator: End sealing pressure ≥ 3.5MPa, core rod acid solubility ≤ 0.1%.   

-Intelligent upgrade of the running end:

-Digital twin platform: integrating meteorological/inspection data to predict remaining lifespan (error ≤ 8%);   

-Electric cleaning robot: suitable for heavily polluted areas with a salt density value ≥ 0.2mg/cm 2.   

Authoritative basis: DL/T 864-2020 "Guidelines for the use of composite insulators for AC overhead lines with nominal voltage above 1000V", IEC 62231-2016 "Composite post insulators"