In the context of Overhead transmission lines (OHTL), a "blown" or failed line is typically caused by a variety of factors, both natural and man-made. The most common causes include:

• Severe Weather: This is the leading cause, with events like lightning strikes, high winds, heavy ice accumulation, and storms placing immense stress on the conductors and support structures.

• Vegetation Interference: Trees and other plant life growing too close to the lines can cause short circuits and ground faults, especially during high winds.

• Equipment Failure: The natural aging or malfunction of components such as insulators, conductors, and hardware can lead to a line failure.

• Human Error: Mistakes during maintenance, construction, or other activities near the lines can result in accidental contact and damage.