Auxiliary DC Control Power System Design for Substations

The most critical component of a protection, control, and monitoring system is the auxiliary DC control power system. Failure of the DC control power can render fault detection devices unable to detect faults, breakers unable to trip for faults, local and remote indication to become inoperable, etc. The auxiliary DC control power system consists of the battery, battery charger, distribution system, switching and protective devices, and any monitoring equipment. Proper sizing, design, and maintenance of the components that make up the auxiliary DC control system are required. Many references for stationary battery system design address only a specific battery technology, making it difficult to compare different types of batteries for their overall suitability to substation application. Also, most references do not address the particular requirements of the electrical substation environment and duty cycle. This paper provides an overall review of things to consider in designing the auxiliary DC control power system for an electrical substation