VAMP 265, Инструкции по эксплуатации и настройке

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2.3 General features of protection
stages 2 Protection functions Technical description
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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 5.4.
Blocking
Any protection function, except arc protection, can be blocked
with internal and external signals using the block matrix
(chapter 5.5). Internal signals are for example logic outputs and
start and trip signals from other stages and external signals
are for example digital and virtual inputs.
Some protection stages have also inbuilt blocking functions. For
example under-frequency protection has inbuilt under-voltage
blocking to avoid tripping when the voltage is off.
When a protection stage is blocked, it won't pick-up in case of a
fault condition is detected. If blocking is activated during the
operation delay, the delay counting is frozen until the blocking
goes off or the pick-up reason, i.e. the fault condition,
disappears. If the stage is already tripping, the blocking has no
effect.
Retardation time
Retardation time is the time a protection relay needs to notice,
that a fault has been cleared during the operation time delay.
This parameter is important when grading the operation time
delay settings between relays.
Figure 2.3-1. Definition for retardation time. If the delay setting would be
slightly shorter, an unselective trip might occur (the dash line pulse).