Understanding fault characteristics of inverter-based distributed energy resources

Original publisher: Golden, CO : National Renewable Energy Laboratory, 2010. OCLC Number: (OCoLC)503162887 Subject: Distributed resources (Electric utilities) Excerpt: ... 3 Short Circuit Analysis Short-circuit studies ensure that the wide range of electrical equipment used to generate, transmit, and distribute electrical power is sufficiently sized to interrupt or withstand short-circuit current. Electrical equipment and protective devices must be properly sized and set for such events. However, short circuits on the EDS cannot be eliminated completely. Instead, the overall goal is to mitigate and, to a certain extent, contain their damaging effects ( IEEE 1997 ). The first goal for short-circuit protection is to clear faults quickly to prevent fires and explosions and further damage to utility equipment such as transformers and cables ( Short 2004 ). The second goal is to establish practices that reduce the impact of faults and improve the following.�Reliability by properly coordinating protective devices to isolate the smallest possible portion of the system and affect the fewest customers.�Power quality by reducing the duration of voltage sags. Coordination practices affect the number and severity of momentary interruptions ( Short 2004 ). There are several types of faults that can occur on the EDS. A 3-phase fault occurs when all three phases come into contact with each other and is the least common type of fault. A single line-to-ground fault is the most common type of short circuit and occurs when one phase of the transmitted power comes into contact with alternative current path or ground. For example, a tree limb inadvertently falls across a power line. A line-to-line fault occurs when two electrical phases come into contact with each other. The 3-phase fault current typically provides the highest available fault current. However, there are situations where this is not the case. For instance, if a single line-to-ground fault occurs and there is an eff...