Strength testing for overhead power transmission lines and their components, including stringing pulley blocks, falls under comprehensive design standards to ensure reliability and safety.The overarching principles for transmission line design and component strength provide context:

Design Standards and Load Conditions:

• Transmission line components, including supports, conductors, and hardware, are designed to meet specific strength limit states and withstand various load conditions .

• International standards like IEC 60826 specify loading and strength requirements for overhead lines, derived from reliability-based design principles . These standards apply to lines 45 kV and above but can be extended to lower voltages .

• Design standards incorporate load factors and combinations, sometimes including coincident temperature design values .

• Components must maintain mechanical integrity without permanent structural deformation under ultimate load conditions .

Component-Specific Considerations:

• For pulling equipment such as tensioners and pullers, which work in conjunction with stringing blocks, requirements include features like a holding brake to maintain conductor tension in case of drive unit failure, and an overload device to automatically stop the puller if tension exceeds a set maximum .

• Puller bullwheels, analogous to pulley block sheaves, have requirements for groove surfaces and minimum diameter (greater than 25 times the rope diameter) to prevent premature wear on the pulling rope .

• Although not directly about pulley blocks, the design of steel poles and other supports also includes minimum yield strength requirements, with testing focused on ensuring compliance with load cases .

These components are subject to rigorous design and manufacturing standards that ensure they can safely handle the mechanical stresses and loads encountered during transmission line stringing, in line with the broader requirements for overhead line construction and operation.