4.9.3
Functionality
The arc protection function ARCSARC detects arc situations in air insulated metal-
clad switchgears caused by, for example, human errors during maintenance or
insulation breakdown during operation.
The function detects light from an arc either locally or via a remote light signal.
The function also monitors phase and residual currents to be able to make accurate
decisions on ongoing arcing situations.
The function contains a blocking functionality. Blocking deactivates all outputs and
resets timers.
4.9.4
Operation principle
The function can be enabled and disabled with the
Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of ARCSARC can be described by using a module diagram. All the
modules in the diagram are explained in the next sections.
OPERATE
Level
detector
1
I_A
I_B
I_C
BLOCK
Level
detector
2
Io
FLT_ARC
REM_FLT_ARC
ARC_FLT_DET
Operation
mode
selector
t
Dropoff
OPR_MODE
t
Dropoff
Figure 391: Functional module diagram
Level detector 1
The measured phase currents are compared phasewise to the set
Phase start value.
If the measured value exceeds the set
Phase start value, the level detector reports
the exceeding of the value to the operation mode selector.
Level detector 2
The measured residual currents are compared to the set
Ground start value. If the
measured value exceeds the set
Ground start value, the level detector reports the
exceeding of the value to the operation mode selector.
Operation mode selector
Depending on the
Operation mode setting, the operation mode selector makes
sure that all required criteria are fulfilled for a reliable decision of an arc fault
situation. The user can select either "Light+current", "Light only" or "BI controlled"
operation mode. The operation is based on both current and light information in
Protection functions
1MRS757644 H
750
620 series
Technical Manual
