T-type line clamps are essential fittings used to connect a main conductor to a branch line, facilitating the transmission of electrical loads while also supporting mechanical stresses. High voltage transmission lines serve as critical links between substations, making them a vital part of the power grid.

Challenges with T-Type Line Clamps

Due to their exposure to outdoor environments—such as mountainous regions and windy areas—transmission lines experience significant mechanical stress from wind and temperature fluctuations. This leads to alternating bending and straightening of the conductors, particularly during seasonal changes, which can cause repeated movement at the T-type clamp outlet. Such movement increases the risk of wear and tear, ultimately resulting in conductor breakage and potential line accidents.

Wear and Tear Observations

Usage Duration and Wear:

Under 10 Years: No noticeable wear.

10-15 Years: Minor wear observed in three instances.

Over 15 Years: Severe wear noted in one case.

Wear Analysis:

Among six worn clamps, the most severely affected main conductor experienced a loss of 9 strands (47.3% wear), while the least affected lost 2 strands (10.5% wear). The T-junction line showed a maximum wear of 4 strands (44.5%).

Distribution of Wear:

Wear was more pronounced in the upper conductors compared to lower ones, indicating that the T-type clamps particularly stress the upper lines.

Factors Contributing to Wear

The wear of T-type clamps is closely related to the forces acting on them, which is influenced by terrain, weather conditions, and temperature changes. Key insights include:

1.Force Direction: The clamps experience both upward and downward forces, leading to wear that varies with environmental conditions.

2.Design Considerations: The upper conductors are more susceptible to significant sag changes due to greater span lengths and varying temperatures, while lower conductors experience minimal sag changes.

3.Environmental Impact: In extreme weather, the length of the T-junction can lead to excessive bending, exacerbating wear at the clamp outlet.

Causes of Wear

Based on the analysis, the causes of conductor wear at T-type clamp points include:

1.Significant Sag Changes: The upper conductors experience larger sag variations, leading to changes in grip direction and force distribution at the clamps.

2.Harsh Operating Conditions: The T-type clamps used are designed for substation applications, making them ill-suited for the complex and rugged environments of transmission lines.

3.Reduced Maintenance: Fewer opportunities for inspections and repairs can lead to undetected friction and wear issues.

Solutions for Reducing Wear

To address the identified wear issues, the following solutions can be implemented:

Use of Pre-Stranded Power Fittings: Transitioning to pre-stranded fittings is recommended to minimize conductor wear. These fittings offer several advantages over traditional clamps:

1. Ease of Installation: They require no special tools and can be installed manually.

2. Improved Connection Quality: They provide uniform stress distribution and maintain the mechanical and electrical properties of the conductors.

3. Corrosion Resistance: Made from similar materials as the conductors, they prevent electrochemical corrosion.

4. Superior Conductivity: Coated with a conductive material, they enhance electrical performance

T-Type Pre-Stranded Connection Bars: Specifically designed for connecting the main conductor to branch lines, they ensure a gripping force of no less than 25% of the rated breaking strength of the conductor. Key considerations include:

1. Non-Reusability: Once subjected to tension, they cannot be reused.

2. Specification Requirement: When ordering, provide the specifications of both the main and branch conductors.

3. Preparation Before Installation: Conductors should be cleaned and polished to remove oxidation before applying quality conductive grease.

By implementing these solutions, the reliability and lifespan of T-type connections in high voltage transmission lines can be significantly improved, reducing the risk of wear-related incidents.