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.
- ARC_DETECTED Light signal output for routing indication of locally detected ARC light
- WARNING signal when light intensity is greater than ambient light compensated
- ALARM signal when ARC light persist more than user set time
- SENSOR_FLT when the sensor supervision detects fault in the arc sensor
The function detects light from an arc locally. Locally, the light is captured by light sensors connected to the 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 com-partments of the switchgear, for example, in the busbar compartment, the circuit breaker compartments, the bus riser and the outgoing feeder cable end compartments.
- LOC_FLT_ARC local light binary input signal mapped from FSTADAGGIO ARC_DETECTED output
- Protection stage with phase- and earth-fault current measurement.
The function ARCSARC has light signal from an arc either locally or via a remote light signal.
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.
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.
Arc protection with several protection relays
When using several protection relays, the protection relay protecting the outgoing feeder trips the circuit breaker of the outgoing feeder when detecting an arc at the cable terminations. If the protection relay protecting the outgoing feeder detects an arc on the busbar or in the breaker compartment via one of the other lens sensors, it generates a signal to the protection relay protecting the incoming feeder. When detecting the signal, the protection relay protecting the incoming feeder trips the circuit breaker of the incoming feeder and generates an external trip signal to all protection relays protecting the outgoing feeders, which in turn results in tripping of all circuit breakers of the outgoing feeders. For maximum safety, the protection relays can be configured to trip all the circuit breakers regardless of where the arc is detected.
Below is the possible configuration. REM_FLT_ARC can be connected via binary input or via GOOSE.
Fast BO activation signal selection
For fast binary output activation Fast ARC BO Conn. setting can be used. However, the connection selection must be same as the output connected to circuit breaker.
Arc protection with ALARM functionality with several protection relays
If ALARM is activated it can also be configured to trip the upstream breaker.