| Popis: |
Electric utilities commonly use automatic reclosing to limit the duration of interruptions to customers. Due to the radial nature of distribution feeders, reclosing is historically performed without voltage supervision or synchronism-check. The absence of these schemes represents lower cost, and works well, since traditionally no source other than the substation is present. However, the presence of Distributed Energy Resource (DERs) introduces the concept of more than one source and the risk of island creation. For instance, when the feeder breaker opens, the islanded feeder is likely to drift out of synchronism with the system. Should the breaker reclose when the system and the island are out of phase, potentially damaging transients can result. This paper addresses the risks of equipment damage due to reclosing onto an islanded feeder. Potential damage to transformers, circuit breakers, loads, and the DER itself are discussed. Applicable industry criteria and equipment capability characteristics are presented as well. Three real DER projects are used as case studies and a risk assessment is conducted. Based on the study results, the paper determines the risks of out-of-phase reclosing to power system components in the study cases. |
