Technical description
2 Protection functions
2.3 General features of protection
stages
VM50.EN004
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2.3.
General features of protection stages
Setting groups
Most stages have two setting groups. Changing between setting
groups can be controlled manually or using any of the digital
inputs, virtual inputs, virtual outputs or LED indicator signals.
By using virtual I/O the active setting group can be controlled
using the local panel display, any communication protocol or
using the inbuilt programmable logic functions.
Forcing start or trip condition for testing
The status of a protection stage can be one of the followings:
Ok = ‘
‘
The stage is not detecting any fault.
Blocked
The stage is detecting a fault but blocked by
some reason.
Start
The stage is counting the operation delay.
Trip
The stage has tripped and the fault is still on.
The blocking reason may be an active signal via the block
matrix from other stages, the programmable logic or any digital
input. Some stages also have inbuilt blocking logic. For more
details about block matrix, see chapter 5.5.
Forcing start or trip condition for testing purposes
There is a "Force flag" parameter which, when activated, allows
forcing the status of any protection stage to be "start" or "trip"
for a half second. By using this forcing feature any current or
voltage injection to the device is not necessary to check the
output matrix configuration, to check the wiring from the
output relays to the circuit breaker and also to check that
communication protocols are correctly transferring event
information to a SCADA system.
After testing the force flag will automatically reset 5-minute
after the last local panel push button activity.
The force flag also enables forcing of the output relays.
Start and trip signals
Every protection stage has two internal binary output signals:
start and trip. The start signal is issued when a fault has been
detected. The trip signal is issued after the configured
operation delay unless the fault disappears before the end of
the delay time.
