ABB RELION REX640 Technical Manual page 1088

Protection functions
4.9.6 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 captured either by lens type point sensors or transparent fiber
loop sensors connected to the light sensor input of the relay. This captured light
is guided via optical fiber to the sensor input of the relay, where it is converted
to electrical signal by means of a photo diode. The optical light sensors can be
placed in the various compartments of the switchgear, for example, in the busbar
compartment, the circuit breaker compartments, the bus riser and the outgoing
feeder cable end compartments.
The light detected by the lens sensor inputs is compared to an automatically
adjusted reference level. Each light sensor input has its own reference level. 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
limit, or the earth-fault current the set
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.
Arc protection with one protection relay
In installations, with limited possibilities to realize signaling between protection
relays protecting incoming and outgoing feeders, or if only the protection relay
for the incoming feeder is to be exchanged, an arc protection with a less selective
level can be achieved with one protection relay. In arc detection, the arc protection
stage trips the circuit breaker of the incoming feeder. The maximum recommended
installation distance between the two lens sensors in the busbar area is six meters
and the maximum distance from a lens sensor to the end of the busbar is three
meters.
1088
Ground start value limit, the arc protection
1MRS759142 F
Phase start value
REX640
Technical Manual