What type of insulators shall be used to support open conductors?

The use of porcelain or glass insulators for supporting open conductors is mandated due to their excellent electrical insulating properties and durability. Porcelain and glass are non-conductive materials that can withstand high voltages without breaking down, making them ideal for use in electrical applications where there is exposure to the elements and varying weather conditions. They provide reliable support and insulation, ensuring that the conductors remain safely elevated and insulated from ground or other structures that may cause short circuits or electrical faults.

Additionally, porcelain has a high mechanical strength which helps it resist environmental stressors such as wind, ice, and temperature fluctuations. Glass insulators also offer high transparency, which can be advantageous for monitoring wear and tear. This makes them both effective and practical for use with overhead lines and other open conductor applications in compliance with safety standards as outlined in the NEC (National Electrical Code).

In contrast, materials like plastic and metal do not possess the same level of resistance to environmental factors and electrical breakdown, making them less suitable for supporting open conductors. Wood may decay and isn't inherently designed for high voltage applications, limiting its effectiveness in this context. Thus, using porcelain or glass insulators aligns with industry standards for safety and reliability in electrical installations.