Reliability of various industrial substations

Many utility and industrial substation configurations have been designed to interconnect energy sources and individual industrial load points. The design, protection schemes and operating procedures of a substation configuration directly affect the reliability of the power supply to these load points. When an existing or planned substation configuration is unreliable, the question is: which substation configuration will be more reliable? Another question is: what reliability methodology will account for the protection schemes in place, the operating procedures and the common cause failures of utility supplies? This paper will discuss and present a reliability analysis of eight basic industrial substation configurations that are typically used inside process plants. The zone branch reliability methodology is used to calculate load point reliability indices of each substation configuration. The reliability analysis includes open and short-circuit failure modes of circuit protective devices, operating practices and common cause failures or utility supplies. The significant impact of common cause utility supply failures on load point reliability levels will be presented and discussed in detail.