Blocking logic
There are three operation modes in the blocking functionality. The operation modes
are controlled by the BLOCK input and the global setting "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 IED 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. 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.
4.5.3.5 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.
4.5.3.6 Signals
Table 401: ROVPTOV Input signals
Name
Type Default Description
Uo SIGNAL 0 Residual voltage
BLOCK BOOLEAN 0=False Block signal for activating the blocking mode
1YHT530004D05 D Section 4
Protection functions
615 series 483
Technical Manual
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