Low Voltage Supply and Controls

Supply
Factories that require medium or high voltage supply from the electric utility can have a dedicated sub-station. These substations step down voltages levels and distribute to buildings throughout the property.

However, not all factories require high or medium voltages. Some require low voltages of 240, 480, or 600 VAC from utilities. In this instance, power is routed directly the distribution system of the plant. 

High and extra-high voltages are associated with supply transmission from the power plant. The reason for transmitting power at high and extra-high voltage levels is to increase efficiency. The lower current accompanying the high voltage transmission allows for the use of thinner lighter-weight cables. This reduces the cost in the tower and electrical line construction. High voltages range from 115,000 to 230,000 VAC and Extra-High voltages range from 345,000 to 765,000 VAC.

The United States transmits up to 500,000 volts on the high voltage grid. High voltages require specialized switching and distribution panels. The control rooms have redundant switching capabilities. They can be controlled remotely or placed in a manual for maintenance and testing of individual supply systems. Sub-stations provide stepped down voltage distributed to localized areas. Ultra-High voltages are voltages that are over 765,000 to 1,100,000 VAC. China is using the highest voltage transmission at 800,000 VAC. They are developing a 1,100,000 VAC system using cables rated at 1,200,000 VAC today.