39
The REF 542plus is a protection and control unit and the programmed automation
logic is executed cyclically in a PLC
–
style mode. The cycle time, in the range of ten
millisecond, is depending upon the logic complexity.
The REF 542plus has an internal fixed compensation both for the relay output
contact actuation time and for the logic execution time. Nevertheless, the actual trip
information processing time depends upon the complexity of the actual logic
programmed inside the unit.
As a result, the protection reaction time, in the worst case, can be the user-defined
preset delay plus twice the cycle time.
Direct channel
In extremely demanding applications, the protection has to react as fast as possible
and the system behavior has to be absolutely deterministic. The REF 542plus offers
then to the protection system designer the direct channel option.
Using this option, the programmed logic execution flow inside the unit is skipped
and the trip command is instantly delivered to the switching object representing the
circuit breaker. All the interlocking conditions are nevertheless respected and
assured. Should the circuit breaker be blocked for any reason, for example,
insufficient SF6 pressure, the trip command is not actuated. The direct channel
option grants then an absolutely deterministic behavior to the REF 542plus
protection functions.
6.2.
Protection functions technical data
The following Table 6.2.-1 illustrates the protection functions technical data.
Table 6.2.-1
ANSI code Protection function and parameters
Current protection functions
68
Inrush stabilization
(only in connection
with 50 and 51)
N = 2.0
…
8.0
M = 3.0
…
4.0
Time = 200
…
100 000 ms
68
Inrush harmonic
Min current threshold = 0.05 ... 40.00 In
Fault current threshold = 0.05 ... 40.00 In
Harmonic ratio threshold = 5 ... 50 %
50
Overcurrent
instantaneous
I>>> = 0.100 ... 40.000 In
t = 15 ... 30 000 ms
51
Overcurrent high
I>> = 0.05 ... 40.00 In
t = 20 ... 300 000 ms
51
Overcurrent low
I > = 0.05 ... 40.00 In
t = 20 ... 300 000 ms
51 IDMT
Overcurrent IDMT
(inverse definite
minimum time)
Inverse time characteristics: Normal, Very, Extreme and
Longtime
Ieb = 0.050 ... 40.000 In
K = 0.050 ... 1.500
Multifunction Protection and Switchbay Control
Unit
Technical Reference Manual
REF 542plus
REF 542plus
1MRS755859
