4.5.3.3 Functionality
The residual overvoltage protection ROVPTOV is used in distribution networks
where the residual overvoltage can reach non-acceptable levels in, for example,
high impedance earthing.
The function starts when the residual voltage exceeds the set limit. ROVPTOV
operates with the definite time (DT) characteristic.
The function contains a blocking functionality. It is possible to block function
outputs, the definite timer or the function itself, if desired.
4.5.3.4 Operation principle
The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of residual overvoltage protection can be described by using a
module diagram. All the modules in the diagram are explained in the next sections.
A070748 V2 EN
Figure 255: Functional module diagram. Uo represents the residual voltage.
Level detector
The residual voltage can be selected with the Uo signal Sel setting. The selectable
options are "Measured Uo" and "Calculated Uo". The residual voltage is compared
to the set Start value. If the value exceeds the set Start value, the level detector
sends an enable signal to the timer.
Timer
Once activated, the timer activates the START output. The time characteristic is
according to DT. When the operation timer has reached the value set by Operate
delay time, the OPERATE output is activated. If the fault disappears before the
module operates, the reset timer is activated. If the reset timer reaches the value set
by Reset delay time, the operate timer resets and the START output is deactivated.
The timer calculates the start duration value START_DUR, which indicates the
percentage ratio of the start situation and the set operation time. The value is
available in the monitored data view.
Section 4 1YHT530004D05 D
Protection functions
482 615 series
Technical Manual
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