Arc Flash Energy Calculation Methods and Challenges for Microgrids

Abstract

Arc flash hazards must be considered to work safely on any electrical system. Microgrids can contain several types of electrical systems working together. These systems commonly include medium and low voltage AC, DC energy storage, and DC photovoltaic (PV) electrical systems. Because the arc behavior and considerations vary from system to system, each of these types of electrical systems can require different methods of estimating the possible arc flash incident energy released during an event. Microgrids also present several challenges in performing arc-flash incident energy calculations, including significantly varying short-circuit current levels across grid-tied and islanded operation, bi-directional fault current flow, and protection complexity. These challenges in microgrids can require special attention when analyzing arc flash incident energy levels and associated arc flash hazards. This paper provides an overview of the types of electrical systems and sources found in a typical microgrid; what methods can be used to calculate incident energy in each system. A novel approach of calculating the Arc Flash energy for multiple time-var-ying AC sources of fault current can be considered in an arc flash calculation by doing a piecewise integration. For the calculation, a single source can be represented by several resources if their contribution is time-varying. Although this approach has been applied to many recent analytical studies performed by authors, further verification through analyses is recommended.