“Light+current” mode, on light information only in “Light only” mode or on remotely
controlled information in “BI controlled” mode. When the "BI controlled" mode is
in use and the OPR_MODE input is activated, the operation of the function is based
on light information only. When the OPR_MODE input is deactivated, the operation
of the function is based on both light and current information. When the required
criteria are met, the drop-off timer is activated.
Drop-off timer
Once activated, the drop-off timer remains active until the input is deactivated or at
least during the drop-off time. The BLOCK signal can be used to block the OPERATE
signal or the light signal output ARC_FLT_DET.
4.9.5 Application
The arc protection can be realized as a stand-alone function in a single relay or
as a station-wide arc protection, including several protection relays. If realized
as a station-wide arc protection, different tripping schemes can be selected for
the operation of the circuit breakers of the incoming and outgoing feeders.
Consequently, the relays in the station can, for example, be set to trip the circuit
breaker of either the incoming or the outgoing feeder, depending on the fault
location in the switchgear. For maximum safety, the relays can be set to always trip
both the circuit breaker of the incoming feeder and that of the outgoing feeder.
The arc protection consists of:
• Optional arc light detection hardware with automatic backlight compensation
for lens type sensors
• Light signal output ARC_FLT_DET for routing indication of locally detected light
signal to another relay
• Protection stage with phase- and earth-fault current measurement.
The function detects light from an arc either locally or via a remote light signal.
Locally, the light is detected by lens sensors connected to the inputs Light sensor
1, Light sensor 2, or Light sensor 3 on the serial communication module of the
relay. The lens sensors can be placed, for example, in the busbar compartment, the
breaker compartment, and the cable compartment of the metal-clad cubicle.
The light detected by the lens sensors is compared to an automatically adjusted
reference level. Light sensor 1, Light sensor 2, and Light sensor 3 inputs have their
own reference levels. When the light exceeds the reference level of one of the inputs,
the light is detected locally. When the light has been detected locally or remotely
and, depending on the operation mode, if one or several phase currents exceed the
set
Phase start value
limit, or the earth-fault current the set
Ground start value
limit,
the arc protection stage generates an operation signal. The stage is reset in 30 ms,
after all three-phase currents and the earth-fault current have fallen below the set
current limits.
The light signal output from an arc protection stage ARC_FLT_DET is activated
immediately in the detection of light in all situations. A station-wide arc protection
is realized by routing the light signal output to an output contact connected to
a binary input of another relay, or by routing the light signal output through the
communication to an input of another relay.
It is possible to block the tripping and the light signal output of the arc protection
stage with a binary input or a signal from another function block.
1MRS757644 H
Protection functions
620 series
Technical Manual
751
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