The word “efficiency” is not often associated with a power distribution system; however, following the appropriate protocol for conducting short circuit and coordination studies can help improve efficiency and safety for your building’s power distribution system.
Short circuit and coordination studies are especially important for both normal and emergency power distribution systems within healthcare facilities where the loss of power can adversely affect patient care.
Both the National Electric Code (NEC) and the National Fire Protection Association (NFPA) recognize the importance of proper systems design and coordination and require that overcurrent protective devices within emergency and other power systems be coordinated to optimize safety and efficiency. When properly implemented, short circuit and coordination studies provide the means to validate the equipment selection process as well as the overall design in order to meet NEC and NFPA code requirements.
The process begins with a single-line diagram—sometimes referred to as a power riser. This diagram serves as a road map of your power distribution system. The single-line depicts all of the major components of a system and shows how they are inter-connected. For new construction, a single-line diagram must be included in the electrical design; and for existing facilities, the information on the existing single-line should be validated using data from field surveys.
Short Circuit Analysis
The next step is to perform a short circuit analysis using the single-line diagram. The goal of this analysis is to verify that each component in the power distribution system is rated to withstand the effects of a “worst case” electrical fault. Per Code, the ampere interrupting capacity (AIC) of each component should be greater than the “worst case” fault current that the component could experience. Where the analysis shows otherwise, there is potential for collateral damage to nearby equipment, or even personal injury from an arc-flash incident. Corrective actions can vary, but should be initiated as soon as the deficiencies are discovered.
The coordination study is finalized after the short circuit analysis has been completed. The purpose of the coordination study is to minimize power distribution downtime by isolating faults with the nearest line side over-current protective device. A coordination study will identify components within a power distribution system that are not properly sized or adjusted. For circuit breakers, corrective action may only involve changing some settings on the front of the breaker, but could require replacing the entire breaker. Each situation must be analyzed on a case-by-case basis.
As a result of implementing a short circuit analysis and coordination study, your system will become more economical, more efficient and safer for building owners and occupants. If you are interested in more information on short circuit and coordination studies, please contact Ted Kopey, PE at email@example.com or (717) 845-7654.