Power surges occur daily and the equipment within your own facility accounts for roughly 80% of all disturbances. As a result, surge protection devices (SPD) are being used at more facilities to protect sensitive control equipment. However, there is some confusion when trying to understand certain ratings. Three ratings that are commonly confused or misunderstood are "Max Surge Rating" (Imax), "Nominal Discharge Current" (In), and "Short Circuit Current Rating" (SCCR). Because all three of these ratings use the same unit of measure (kA), they are easily confused with one another.