16
NT935 ETH
TEMPERATURE SENSOR DIAGNOSTICS
In case of failure or exceeded full scale value of one of the thermometric sensors installed on the machine to protect, the
FAULT relay opens immediately with the relative warning of faulty sensor on the corresponding channel (PT err).
Fcc indicates sensor short-circuited or minimum full scale value of the control unit exceeded -8°C (version 0°÷240°C)
and -48°C (version -40°C÷200°C)
Foc indicates sensor interrupted or maximum full scale value of the control unit exceeded 243°C (version 0°÷240°C)
and 203°C (version -40°C÷200°C)
To eliminate the message and reset the opening of the Fault contact, it is necessary to check the Pt100 connections and
replace the faulty sensor (if any). If the minimum/maximum full scale value has been reached, check that the ambient
conditions match the control unit reading.
Note: exceeding the minimum/maximum full scale value can also be caused by interference on the sensor lines; in this
case we recommend that you check:
the correct installation of the sensors and above all of the extension cable (as stated in the paragraph MEASUREMENT
SIGNAL TRANSFER)
the activation of: VOTING (see below) or FCD (see page 31) according to the conditions of the system.
CAL message display: it appears when damage is found in the measurement circuit. 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 redundancy principle, we use the sensors installed on the three phases U-V-W to monitor the transformer's
operation, and at the same time ascertain the sensors are working correctly, discriminating against any false alarms
(generated by installation errors).
By activating the
VOTING "YES"
function, the control unit compares the temperature values recorded on the monitored
CH1-CH2-CH3 channels and enables the switching of the
TRIP
contact only if the
TRIP
threshold has been exceeded on
at least two channels over the same period T.
By selecting
VOTING
“NO”
the function will be disabled.
Note: by setting Voting "Yes" the switching of the
ALARM
contact will anyway indicate the alarm threshold on each
individual channel has been exceeded.
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-FCC-FCD on two or more channels, with active
voting, can determine the TRIP contact inhibition.
PROGRAMMED DATA DIAGNOSTICS
In case of failure of the internal memory or corruption of programmed data, just after switching on,
Ech
appears with the
relevant Fault contact.
In this case, for safety reasons, the default parameters are loaded automatically (see programming table on pages 13-14).
Eliminate
Ech
by pressing RESET and run programming to enter the desired values.
Finally switch the unit off and back on to check the memory works correctly, if it is damaged
Ech
will be displayed again
(send the control unit to TECSYSTEM srl for repairs).
TEMPERATURE DIAGNOSTICS
When one of the temperature sensors senses a temperature 1°C higher than the alarm threshold, 5 seconds later the
ALARM
relay switches and the
ALARM
LED of the affected channel (CH
n
) lights up.
When the trip temperature limit is exceeded, the
TRIP
relay switches and the
TRIP
LED of the affected channel (CH
n
)
lights up.
As soon as the recorded temperature returns to values equal to or lower than the limit set for the
ALARM
and
TRIP
relays
switching, these relays de-energise and the corresponding LEDs switch off.
The
ALARM
and
TRIP
values are kept in the internal memory: they can be recalled by entering the Vis modes
(programmed parameter display) and modified in PRG (programming) mode.
