Bender VMD4105-D-2 B93010045 Hoja De Datos
Los códigos de productos
B93010045
Function
18
3.2.10 Passive islanding detection (df/dt)
The VMD460-NA uses a passive method for islanding detection (three-phase
voltage and frequency monitoring).
voltage and frequency monitoring).
df/dt
The monitoring of the rate of change of frequency "ROCOF" (df/dt) is an
islanding detection function.
If a section of the network is disconnected by the energy provider, it may hap-
pen that the power generation systems located in this section unintentionally
feed this section of the network.
Underfrequency and overfrequency monitoring might not be sufficient to de-
tect this dangerous, uncontrollable state, since the generators try to keep the
frequency at the nominal frequency level.
islanding detection function.
If a section of the network is disconnected by the energy provider, it may hap-
pen that the power generation systems located in this section unintentionally
feed this section of the network.
Underfrequency and overfrequency monitoring might not be sufficient to de-
tect this dangerous, uncontrollable state, since the generators try to keep the
frequency at the nominal frequency level.
Due to the unbalance between generated and consumed energy, however,
the frequency fluctuates around the nominal frequency. If this happens at a
certain minimum speed, this is an indication of islanding, hence the power
generation system will be disconnected by the VMD460-NA.
the frequency fluctuates around the nominal frequency. If this happens at a
certain minimum speed, this is an indication of islanding, hence the power
generation system will be disconnected by the VMD460-NA.
As soon as the rate of change of frequency is below the response value
hysteresis and t
hysteresis and t
on
has expired, the power generation system will be recon-
nected.
t
off
Response delay: the time during which a limit value
(df/dt) must be violated until the power generation
system is disconnected by the VMD460-NA.
(df/dt) must be violated until the power generation
system is disconnected by the VMD460-NA.
t
on
Delay time, if df/dt disconnected the system.
Measuring window
Period of time used to calculate the average of the fre-
quency changes. The bigger the measuring window is
selected the less sensitive will the df/dt function be.
quency changes. The bigger the measuring window is
selected the less sensitive will the df/dt function be.