Calculations > Voltage dip analysis

Apart from the sudden increase of load currents and transients, voltage drops particularly result from short-circuits in the electricity network. The deepest break-downs are caused by 2- and 3-phase short-circuits, which may cause the line-to-line voltage to drop down to 0 %.

Voltage drops are transferred by the faulted network through the transformers into all following nets. E.g. one short-circuit in the medium voltage network induces voltage dips in all connected low-voltage systems. The lower the voltage level, the more frequently voltage drops occur, since the fault frequency in the network is higher and dips from higher voltage networks are transferred to all connected lower voltage systems.

For the duration of the voltage drops the protection devices are of crucial influence. Voltage dips can lead to malfunctions of connected devices. Thereby, computer systems and electric drives are particularly endangered.

By means of fault statistics and short-circuit current calculation, for every point in the network its statistically expected frequency of voltage dips can be calculated in both dip depth and duration. The fault statistics thereby determines the frequency, the short-circuit calculation the depth and the protection device in the network the theoretical duration of the voltage dips.

The voltage dips are categorised as follows:

•nine voltage categories in steps of 10%

•nine duration categories:

▪< 20 ms

▪20 ... 100 ms

▪100 ... 300 ms

▪300 ... 500 ms

▪0.5 ... 1 s

▪1 ... 2 s

▪2 ... 5 s

▪5 ... 10 s

▪> 10 s

Voltage dip analysis: General

Voltage dip analysis: General