During the research the interruptions in 20 kV distribution
network in Latvia were investigated without taking into
account massive interruptions cases. Situation of massive
interruptions is formed under particular conditions that result in
repeatedly increasing interruption frequency, then the
reliability calculations require separate consideration of
massive interruptions cases. Not only were the interruptions
during the defined time period analyzed but also the process of
each interruption of the supply system elimination, duration
and distribution. In relation with the registered operative
interruptions statistical data the following information about
the interruptions was analyzed: about the time of event
beginning, about the interruption and sectioning operation,
disappearance of voltage, overloading or acute changes in the
operation regimes of the elements (load, voltage, temperature,
etc.) or about increasing of voltage over the admissible level.
Having analyzed the interruptions for the period of three years
under normal weather conditions and using distribution
network data the interruptions frequency and duration for
power switches, overhead lines, cable lines, breakers and
20/0.4 kV transformer substation (TS) were calculated.
Average parameters of the frequency and duration of
interruptions in the world are applied also for the comparison
(Table I).