ANALYSIS OF RELIABILITY OF NONRECTORABLE REDUNDANT POWER SYSTEMS TAKING INTO ACCOUNT COMMON FAILURES

Reliability Analysis of nonrestorable redundant power Systems of industrial plants and other consumers of electric energy was carried out. The main attention was paid to numbers failures influence, caused by failures of all elements of System due to one general reason. Noted the main possible reasons of common failures formation. Two main indicators of reliability of non-restorable systems are considered: average time of no-failure operation and mean probability of no-failure operation. Modeling of failures were carried out by mean of division of investigated system into two in-series connected subsystems, one of them indicated independent failures, but the other indicated common failures. Due to joined modeling of single and common failures resulting intensity of failures is the amount incompatible components: intensity statistically independent failures and intensity of common failures of elements and system in total.It is shown the influence of common failures of elements on average time of no-failure operation of system. There is built the scale of preference of systems according to criterion of  average time maximum of no-failure operation, depending on portion of common failures. It is noticed that such common failures don’t influence on the scale of preference, but  change intervals of time, determining the moments of systems failures and excepting them from the number of comparators. There were discussed two problems  of conditionally optimization of  systems’  reservation choice, taking into account their reliability and cost. The first problem is solved due to criterion of minimum cost of system providing mean probability of no-failure operation, the second problem is solved due to criterion of maximum of mean probability of no-failure operation with cost limitation of system

АНАЛИЗ НАДЕЖНОСТИ НЕВОССТАНАВЛИВАЕМЫХ РЕЗЕРВИРОВАННЫХ СИСТЕМ ЭЛЕКТРОСНАБЖЕНИЯ С УЧЕТОМ МНОЖЕСТВЕННЫХ ОТКАЗОВ

Reliability Analysis of nonrestorable redundant power Systems of industrial plants and other consumers of electric energy was carried out. The main attention was paid to numbers failures influence, caused by failures of all elements of System due to one general reason. Noted the main possible reasons of common failures formation. Two main indicators of reliability of non-restorable systems are considered: average time of no-failure operation and mean probability of no-failure operation. Modeling of failures were carried out by mean of division of investigated system into two in-series connected subsystems, one of them indicated independent failures, but the other indicated common failures. Due to joined modeling of single and common failures resulting intensity of failures is the amount incompatible components: intensity statistically independent failures and intensity of common failures of elements and system in total.It is shown the influence of common failures of elements on average time of no-failure operation of system. There is built the scale of preference of systems according to criterion of  average time maximum of no-failure operation, depending on portion of common failures. It is noticed that such common failures don’t influence on the scale of preference, but  change intervals of time, determining the moments of systems failures and excepting them from the number of comparators. There were discussed two problems  of conditionally optimization of  systems’  reservation choice, taking into account their reliability and cost. The first problem is solved due to criterion of minimum cost of system providing mean probability of no-failure operation, the second problem is solved due to criterion of maximum of mean probability of no-failure operation with cost limitation of system.Произведен анализ надежности невосстанавливаемых резервированных систем электроснабжения промышленных предприятий и других потребителей электрической энергии. Основное внимание уделено влиянию множественных отказов, вызванных отказами всех элементов системы по одной общей причине. Указаны основные возможные причины возникновения множественных отказов. Рассматриваются два основных показателя надежности невосстанавливаемых систем: среднее время безотказной работы и средняя вероятность безотказной работы. Моделирование отказов производили путем разделения исследуемой системы на две последовательно включенные подсистемы, одна из которых отражает независимые отказы, а другая – множественные отказы. В соответствии с совместным моделированием одиночных и множественных отказов результирующая интенсивность отказов представляет собой сумму взаимоисключающих составляющих: интенсивности статистически независимых отказов и интенсивности множественных отказов элементов и системы в целом.Показано существенное влияние множественных отказов элементов на среднее время безотказной работы системы. Построена шкала предпочтений систем по критерию максимума среднего времени безотказной работы в зависимости от доли множественных отказов. Отмечено, что на шкалу предпочтений по критерию средней вероятности безотказной работы множественные отказы не влияют, однако изменяют интервалы времени, определяющие моменты отказа систем и исключения их из числа сравниваемых. Рассмотрены две задачи условной оптимизации выбора системы резервирования с учетом ее надежности и стоимости. Первая задача решается по критерию минимальной стоимости системы при условии обеспечения заданной средней вероятности безотказной работы, вторая – исходя из критерия максимума средней вероятности безотказной работы при ограничении на стоимость системы.