1MRS751802-MUM
REX 521
99
Protection Relay
Technical Reference Manual, Standard Configurations
7.1.10. O->I
The majority (about 80...85%) of MV overhead line faults are transient and are
automatically cleared by momentarily de-energizing the line, whereas the rest of the
faults (15...20%) can be cleared by longer interruptions. The de-energization of the
fault place for a desired period of time is implemented by auto-reclose relays or
functions. The auto-reclosers are capable of clearing most of the faults. At a
permanent fault, the auto-reclosing is followed by final tripping. A permanent fault
has to be located and cleared before the fault location can be re-energized.
The auto-reclose function O->I can be used for auto-reclosing together with any
circuit breaker that has the characteristics required for auto-reclosing. The function
block provides five programmable auto-reclose shots which can perform one to five
successive auto-reclosures of desired type and duration, such as one high-speed and
one delayed auto-reclosure. When the reclosing is initiated by the start of a
protection function, the auto-reclose function is capable of executing the final trip of
the circuit breaker in a short operate time in case the fault still persists when the last
reclosure selected has been carried out.
Fig. 7.1.10.-1 Function block symbol of O->I
Three-phase thermal overload protection for cables, 3Ith>
Time constant for the cable
Maximum load current for the cable
Maximum temperature of conductor
Reference temperature
Trip temperature
Prior alarm temperature
Reclosure temperature
Ambient temperature
1…999 min
1.0…5000.0 A
40.0…150.0°C
-50.0…100.0°C
80.0…120.0%
40.0…100.0%
40.0…100.0%
-50.0…100.0°C
Operation accuracy
Reset ratio
Note! The values below apply when f/fn = 0.95...1.05
±1.0%, I = 0.1...10.0 x In
Trip: (Calculated temp. rise - 0.1) / Trip temperature
Start: (Calculated temp. rise - 0.1) / Prior alarm
temperature
O−−>I
AR1
AR2
AR3
AR4
ARINH
CBOPEN
CBCLOSE
ON
RESET
DEFTRIP
LOCKOUT
ROPEN
RCLOSE
SHOT1
SHOT2
SHOT3
SHOT4
SHOT5
AR1TRIP
AR2TRIP
AR3TRIP
AR4TRIP
CB FAIL
DEFTRIP
LOCKOUT
TRDUE
TDDUE
ACTIVE
SHOT_ALARM
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