What is the typical DC voltage found at transmission substations?

Transmission substations commonly utilize a DC voltage of 125 volts. This standard is widely adopted because it provides a reliable power source for different control systems, protection relays, and communication devices utilized within substations. The 125VDC system is often derived from battery banks that serve to ensure uninterrupted service during power outages or grid disruptions. This voltage level is optimal—balancing safety, efficiency, and capability for substation operations.

Other voltages, such as 48VDC, are typically used in telecommunications and certain electronic applications. Although 120VDC can be convenient in some industrial settings, it is less standard than 125VDC for substation applications. 240VDC is usually considered too high for most control and safety equipment within substations, as it may pose increased risks and demand for additional safety measures. Thus, the selection of 125VDC aligns most closely with the operational needs and safety standards in transmission substations.