Which of the following is not a way to sag wire accurately?

Sagging wire accurately is crucial for ensuring the stability and safety of power lines. The correct answer highlights an option that is not typically used for measuring wire sag.

Wind resistance calculation involves assessing how wind forces interact with the wire, which can indeed affect sag but is not a direct method for measuring or setting sag accurately in the installation process. The wind can cause fluctuations, and calculating its impact does not provide a tangible measurement of the wire's sag at any given time.

On the other hand, the other methods mentioned—using a dynamometer, the target method (scope), and the return-wave method—are all established means for accurately determining the sag. A dynamometer measures the tension in the wire, which can be used to calculate sag effectively. The target method utilizes a visual reference to gauge the wire's position, while the return-wave method employs electrical principles to determine sag based on wave propagation.

By focusing on direct measurement techniques, the effectiveness of these methods in establishing accurate sag becomes clear, distinguishing them from the indirect approach represented by wind resistance calculations.