16
NT538 WS EVO
TEMPERATURE SENSOR DIAGNOSTICS
In case of failure or exceeded full scale value of one of the thermometric sensors installed on the machine to be protected,
the FAULT relay opens immediately with the relative warning of faulty sensor on the corresponding channel.
Fcc indicates sensor in short circuit or exceeding the minimum full scale value of the control unit -8°C (for version 0° ÷
240°C) and -48°C (for version -40°C ÷ 200°C)
Foc indicates sensor interrupted or exceeding the maximum full scale value of the control unit 243°C (for version
0°÷240°C) and 203°C (for version -40°C÷200°C)
To eliminate the message and to restore the Fault opening, check the connections of the Pt100 and replace the faulty sensor
if necessary. In case the minimum/maximum full scale value has been reached, make sure that the environmental conditions
correspond to what is indicated by the control unit.
Note: exceeding the minimum/maximum full scale can also be caused by possible disturbances on the sensor lines, in this
case the following are recommended:
Check correct installation of the sensors and especially of the extension cable (as indicated in the paragraph
MEASUREMENT SIGNALS TRANSFER).
Activation of the functions: VOTING (below) or FCD (on page 19) must always be operated taking into account the working
conditions of the system.
CAL message display: the indication appears when the measurement circuit is damaged. The temperature values displayed
might be incorrect. Return the control unit to TECSYSTEM for repairs.
VOTING FUNCTION
The voting function derives from the redundancy concept that consists in duplicating the components of a system to increase
their
reliability
.
How does VOTING work?
Using the principle indicated, use the installed probes to monitor operation of the controlled electrical machine, but at the
same time ascertain correct functioning of the probes themselves, discriminating any false alarms (generated by installation
errors or failures).
The enabling of
VOTING
can be performed by choosing one of the three selection modes
“1-2-3”
. The control unit performs
a comparison of the temperature values recorded on the monitored channels, enables the switching of the release contact
(
TRIP)
only if it is detected exceeding the
TRIP
threshold on at least two channels in the same period T.
By selecting
VOTING “NO”
the function will be disabled.
The selection tables below show the combinations of channels with active voting available. For greater flexibility
in two combinations we have provided channels with voting enabled and others with disabled voting.
•
Voting enabled: The TRIP contact switches only if at least two channels have exceeded the TRIP threshold.
•
Voting disabled: The TRIP contact switches when the individual channel exceeds the TRIP threshold.
Note: switching the
ALARM
contact will in any case indicate that the alarm threshold has been exceeded on each individual
channel.
To enable the Voting function, read the programming section on pages 13-14.
Attention: To control the transformer correctly from a temperature point of view, enabling the VOTING function
is allowed where the load distributed between the phases of the transformer is adequately balanced. In addition,
any conditions of FAULT: FCC-FOC-FCD on two or more channels, with active voting, can determine the TRIP
contact inhibition.
Selection 1
Selection 2
Selection 3
VOTING ENABLED CH1… ..CH3
VOTING ENABLED CH1…. CH6
VOTING ENABLED CH1…. CH8
1
1
1
2
2
2
3
3
3
VOTING DISABLED CH4..CH8
4
4
4
5
5
5
6
6
6
VOTING DISABLED CH7..CH8
7
7
7
8
8
8
