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.
Blocking logic
There are three operation modes in the blocking function. The operation modes
are controlled by the BLOCK input and the global setting in Configuration >
System > Blocking mode which selects the blocking mode. The BLOCK input can be
controlled by a binary input, a horizontal communication input or an internal signal
of the protection relay's program. The influence of the BLOCK signal activation is
preselected with the global setting
Blocking mode
.
The
Blocking mode
setting has three blocking methods. In the "Freeze timers"
mode, the operation timer is frozen to the prevailing value, but the OPERATE output
is not deactivated when blocking is activated. In the "Block all" mode, the whole
function is blocked and the timers are reset. In the "Block OPERATE output" mode,
the function operates normally but the OPERATE output is not activated.
4.5.5.5 Application
ROVPTOV is designed to be used for earth-fault protection in isolated neutral,
resistance earthed or reactance earthed systems. In compensated networks,
starting of the function can be used to control the switching device of the neutral
resistor. The function can also be used for the back-up protection of feeders for
busbar protection when a more dedicated busbar protection would not be justified.
In compensated and isolated neutral systems, the system neutral voltage, that
is, the residual voltage, increases in case of any fault connected to earth.
Depending on the type of the fault and the fault resistance, the residual voltage
reaches different values. The highest residual voltage, equal to the phase-to-earth
voltage, is achieved for a single-phase earth fault. The residual voltage increases
approximately the same amount in the whole system and does not provide any
guidance in finding the faulty component. Therefore, this function is often used as a
backup protection or as a release signal for the feeder earth-fault protection.
The protection can also be used for the earth-fault protection of generators and
motors and for the unbalance protection of capacitor banks.
The residual voltage can be calculated internally based on the measurement of the
three-phase voltage. This voltage can also be measured by a single-phase voltage
transformer, located between a transformer star point and earth, or by using an
open-delta connection of three single-phase voltage transformers.
4.5.5.6 Signals
Table 613: ROVPTOV Input signals
Name Type Default Description
Uo SIGNAL 0 Residual voltage
BLOCK BOOLEAN 0=False Block signal for activating the
blocking mode
Protection functions 1MRS757644 H
662 620 series
Technical Manual
To Next Page
Loading...
