Electric-power transmission involves the transfer of electrical energy from its generation source to electrical substations located near demand centers such as cities and towns. Transmission lines, when interconnected with each other, become transmission networks. Due to the large amount of power involved, transmission-level voltages are generally considered those above 110 kilo volts (kV). Voltages between 110 kV and 33 kV are typically considered sub-transmission voltages, but are occasionally used for long transmission systems with light loads. Voltages of less than 33 kV are representative of distribution projects. New technologies provide methods to transmit energy in a more efficient and sustainable way, for example with low-loss power transmission. Reliable and low-loss power transmission is an important element of sustainable energy usage. Additionally, alternative methods for transmission line construction are available to help reduce the environmental footprint, such as loss of vegetation, thus improving overall sustainability.