Voltage dips and sensitivity of consumers in low voltage networks

In distribution systems, power quality is of increasing importance as the low voltage consumers use microelectronic components for control and operation, which are sensitive to voltage dips and power interruptions. In an investigation of VEO (Verband der Elektrizitaswerke Osterreichs, Union of Austrian Utilities), the functional sensitivity of low voltage consumers on voltage dips was investigated. Short circuit faults and large load variations may cause voltage dips. After system faults, not only voltage dips but also interruptions of longer duration are possible in electrical distribution systems. These phenomena are purely random in nature and their amplitude and duration varies in a significant range. The deviation from the rated voltage caused by a short circuit depends on the fault distance and the short-circuit power of the network. The duration is given by the fault clearing time of the protection and the circuit-breaker. Large load changes, e.g. by motor starting, may result in voltage dips with a duration of up to some seconds, In this paper, the behaviour of different low voltage consumers during the occurrence of voltage reductions is considered. For the investigated devices, the combinations of amplitude and duration of voltage depressions which result in a malfunction are evaluated.