Rockwell Automation 865 Differential Protection Relay - Manual (Page 46)

3-2 Protection Functions
865-UM001A-EN-P – July 2009
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 example an under
frequency stage is blocked if voltage is too low. For more details
about block matrix, see Chapter 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 relay 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 and forcing
the optional mA outputs.
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.
Output Matrix
Using the output matrix the user connects the internal start and trip
signals to the output relays and indicators. For more details see
Chapter 5.