2.15 Overvoltage Protection
259
7UT613/63x Manual
C53000-G1176-C160-2
2.15 Overvoltage Protection
The overvoltage protection has the task of preventing from insulation problems by pro-
tecting electrical equipment against inadmissible abnormally high voltage levels.
High voltages occur in the power station sector, e.g. caused by incorrect manual op-
eration of the excitation system, faulty operation of the automatic voltage regulator,
(full) load shedding of a generator, separation of the generator from the system or
during island operation.
High voltages can also occur in the network by faulty operation of a voltage regulator
on the transformer or on longer weak load.
The overvoltage protection can only be used for three-phase protective objects. This
implies that the device is connected to a voltage transformer. This is therefore only
possible for 7UT613 and 7UT633. As the overvoltage protection only gets its measur-
ing information from the connected voltage measurement, it leaves the assignment of
currents to one side or a measuring location for the function without coating. Setting
causes the same differences as in other protection functions. If the overvoltage pro-
tection is assigned to one side of the main protective object or the three-phase busbar,
the voltage limits in related values (U/UN) have to be set. The values are set to sec-
ondary in volts when assigned to a measuring location.
2.15.1 Function Description
The overvoltage protection assesses the largest of the three phase-to-phase voltages
or the highest of the three phase-to-earth voltages (adjustable).
Overvoltage protection includes two stages. In case of a high overvoltage, the
switchoff is performed with a short-time delay, whereas in case of lower overvoltages,
the switchoff is performed with a longer time delay. Voltage limit values and delay
times can be set individually for both stages.
Furthermore, the entire overvoltage protection can be blocked vie a binary input.
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