Overvoltage Protection U> (59) - Allen-Bradley Rockwell Automation 857 User Manual

3-50
Protection Functions
Overvoltage protection
U> (59)
857-UM001A-EN-P – July 2009
Table 3.27 – Parameters of the Thermal Overload Stage T> (49)
Parameter Value
Status -
Blocked
Start
Trip
Time hh:mm:ss
SCntr
TCntr
Force Off
On
T
MaxRMS
Imax
k>
Alarm
tau
ctau
kTamb
Imax40
Imax70
Tamb
Samb
n/a
ExtAI1...16
For details of setting ranges, see "Protection Stages" in Chapter 10.
Set = An editable parameter (password needed)
C = Can be cleared to zero
F = Editable when force flag is on
The overvoltage function measures the fundamental frequency
component of the line-to-line voltages regardless of the voltage
measurement mode (see "Voltage Measurement Mode" in Chapter 5).
By using line-to-line voltages any phase-to-ground over-voltages
during earth faults have no effect. (The earth fault protection
functions will take care of earth faults.) Whenever any of these three
line-to-line voltages exceeds the user's pick-up setting of a particular
stage, this stage picks up and a start signal is issued. If the fault
situation remains on longer than the user's operation time delay
setting, a trip signal is issued.
Unit Description
Current status of the stage
Estimated time to trip
Cumulative start counter
Cumulative trip counter
Force flag for status forcing for test
purposes. This is a common flag for
all stages and output relays, too.
Automatically reset by a 5-minute
timeout.
% Calculated temperature rise. Trip limit
is 100 %.
Arms Measured current. Highest of the
three phases.
A kxIgn. Current corresponding to the
100 % temperature rise.
xIn Allowed overload (service factor)
% Alarm level
min Thermal time constant
xtau Coefficient for cooling time constant.
Default = 1.0
xIn Ambient temperature corrected max.
allowed continuous current
%In Allowed load at Tamb +40 °C.
Default = 100 %.
%In
Allowed load at Tamb +70 °C.
°C Ambient temperature. Editable
Samb=n/a. Default = +40 °C
Sensor for ambient temperature
No sensor in use for Tamb
External Analogue input 1...16
Note
F
F
C
C
Set
F
Set
Set
Set
Set
Set
Set
Set
Set