Insulating blankets are required for protection on lines energized up to what voltage between phases?

The requirement for insulating blankets aligns with safety protocols regarding electrical voltage levels. Insulating blankets are essential for protecting workers from electrical hazards when working with energized lines. For lines energized up to 21,000 VAC between phases, the use of insulating blankets is mandated because this voltage level presents a significant risk of electrical shock.

The threshold of 21,000 VAC is based on the principles of electrical safety and the insulating properties required to prevent accidental electrical contact. At lower voltages, such as those represented by the other choices, the insulating requirements may not be as stringent, allowing for various forms of personal protective equipment and safety practices to suffice. However, once the voltage exceeds 21,000 VAC, the risk escalates, necessitating the added protection of insulating blankets to ensure worker safety in electrical work environments.

Thus, this voltage level is critical for determining when insulating blankets must be employed to safeguard personnel from the hazards associated with high voltage lines.