ARC FLASH HAZARD CALCULATIONS IN DC SYSTEMS

The calculations of short‐circuit currents in DC systems is essential for the design and application of distribution and protective apparatuses used in these systems and for arc flash calculations. Four types of DC sources can be considered: lead acid storage batteries, DC motors, converters in three‐phase bridge configuration, and smoothing capacitors. Though some literature and calculations examples of short‐circuit currents in DC systems according to ANSI/IEEE publications are available, this chapter uses exclusively IEC equations and methodology because of the comprehensive nature of the IEC equations. The typical time–current curve for rectifiers short‐circuit is shown. The total short‐circuit current at fault is the sum of the partial short‐circuit currents calculated from the various sources. The semi‐conducting devices like diodes, SCRs, GTOs, cannot be allowed to be damaged on short‐circuit currents.