Final answer:
The three loading districts in the context of wire and electrical systems are stages in the generation, transmission, and distribution of electrical power. Transformers reduce high transmission voltages to lower, safer levels for end users' consumption, and the primary voltage in a transformer is higher than the secondary voltage.
Step-by-step explanation:
When talking about wire and electrical systems, the three types of loading districts generally refer to stages in the generation and distribution of electrical power: generation, transmission, and distribution. During transmission, power is sent long distances at high voltages, typically ranging from 120 kV to 700 kV, to limit energy losses. Once the power reaches a more localized setting like a neighborhood or industry, it is stepped down through a substation to lower voltages ranging from 5 to 13 kV, and then further reduced for use in homes, businesses, or industries to even safer levels such as 120, 240, or 480 V. Transformers play a key role in this process, and the primary voltage of a transformer is higher than the secondary voltage, which is also an indication that the primary current will typically be lower than the secondary current due to the conservation of power within the transformer.