How should tempered glass insulators be selected for transmission lines of different voltage levels?

Release time:

2025-11-26

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In the design of transmission lines, the selection of tempered glass insulators should be determined comprehensively based on voltage levels, AC and DC types, environmental conditions (pollution, altitude, icing, etc.) and mechanical load requirements. The core objective is to meet insulation reliability, mechanical safety and economy.

The following are the selection principles and specific suggestions for tempered glass insulators on transmission lines of different voltage levels:

1. Selecting Core Parameters: Key indicators that determine the applicability of insulators

Regardless of the voltage level, when choosing tempered glass insulators, the following core parameters should be prioritized and clarified:

Creepage distance and creepage ratio distance

Creepage distance: The shortest discharge path along the umbrella skirt contour on the insulator surface (unit: mm), which directly affects the anti-pollution flashover capability.

Creepage distance (λ) : The ratio of creepage distance to the highest working voltage of the system (unit: mm/kV), which needs to be determined according to the pollution level (GB/T 16434 divides pollution into 0-IV levels). The higher the level, the greater the required λ (for example, for level IV pollution, λ≥31 mm/kV).

2. Mechanical failure load (rated mechanical load)

The maximum static tensile force that an insulator can withstand (unit: kN) needs to be matched with the tension of the conductor, meteorological loads (wind, ice), and the force on the tower. Common specifications include 70kN, 100kN, 120kN, 160kN, 210kN, 300kN, etc.

3. Number of insulator pieces

The dry arc distance (the shortest air distance between the electrodes at both ends of the insulator) is jointly determined by the voltage level, creepage ratio distance, and altitude correction (the number of pieces needs to be increased when the altitude exceeds 1000m, with an increase of 10% for every 1000m increase) to ensure that it meets the requirements for lightning resistance and operational overvoltage.

4. Umbrella design

Choose according to environmental requirements: regular umbrella (suitable for clean areas), double umbrella/triple umbrella (suitable for moderately dirty and rainy areas, easy to clean), bell-shaped umbrella/deep-edge umbrella (suitable for heavily dirty and ice-covered areas, preventing snow and dirt accumulation).

 

Ii. Selection Process and Standard Basis

1. Determine the basic parameters: Clearly define the line voltage level (AC/DC), wire model (calculate mechanical load), pollution level of the area passed through (check the environmental assessment report), and altitude.

2. Calculate the creepage ratio distance: According to GB/T 50545 "Code for Design of High Voltage Switchgear", determine the minimum creepage ratio distance (for example, AC Class I pollution λ≥16 mm/kV, DC Class I λ≥20 mm/kV).

3. Calculate the number of insulator pieces: The creepage distance of a single piece (e.g., 280mm for standard type) × number of pieces ≥ maximum working voltage × minimum creepage ratio distance, while also considering altitude correction.

4. Matching mechanical load: According to DL/T 544 "General Technical Conditions for DC Power Supply Equipment in Power Systems", the mechanical failure load should be ≥ 2.5 times the maximum service tension of the conductor (safety factor).

5. Verify standard compliance: The products shall comply with international standards such as GB/T 1001.1 "Insulators for overhead lines with Nominal voltage higher than 1000V - Part 1: Porcelain or glass insulators for AC systems" and IEC 61109.

Summary

The selection of tempered glass insulators for different voltage levels should follow the principle that "voltage determines the number of base pieces, environment modifiers the creepage distance, and load matches the mechanical strength" : for low-voltage lines, economic efficiency is emphasized; for medium and high voltages, insulation and mechanical performance need to be balanced; and for ultra-high voltages, extreme parameters and special designs are required. At the same time, it is necessary to combine the specific environment (contamination, altitude, icing) and standard specifications to ensure that the insulator meets the safety operation requirements throughout its entire life cycle.

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