A transmission substation acts as a connection between several transmission lines. A distribution substation acts as a middleman between the transmission substation and the electricity consumer, lowering the transmission voltage to an appropriate level for distribution to family homes and apartment buildings. Since cities and large metropolitan areas have high concentrations of electrical consumers, these places tend to boast highly complicated distribution substations. Other types of substations include the collector substation, often utilized in hydroelectric power plants or wind farms, the switching substation, which is typically built next to a power station to connect and disconnect transmission lines, and the converter substation, which can adjust the frequency of transmission currents.