Application of DC AF Incident Energy Reference Boundary Area Plots in TCCs Considering Input Parameter Variability

This work introduces the concept of dc C-areas in time-current characteristic plots (TCCs) for establishing a reference of dc arc-flash (dc AF) incident energy (IE) during the protection and coordination study. C-area plots represent a constant allowable incident energy for a piece of equipment while considering arc flash input data variability. This work introduces the C-area application for dc equipment. The dc C-area reference plots allow protection engineers to select overcurrent protective device settings in TCCs while keeping track of the allowable incident energy. This work explains the theory and derivation of the dc C-areas, the impact of the input parameter variability, and provides a detailed explanation of the data collection challenges for performing a dc arc-flash incident energy analysis. The dc C-area methods introduced in this paper are based on industry accepted dc arc-flash calculation equations, yet novel concepts in dc C-areas such as arc elongation and conductor erosion effects are discussed along with their effects. This paper also includes application examples of C-areas for battery energy storage systems (BESS) and photovoltaic (PV) systems equipment protection and coordination studies. The protection and coordination device setting selections made by means of dc C-areas are then compared to actual dc arc-flash incident energy calculations performed using commercially available power system analysis software to validate the methodology.