10
NT538 P8 V4-R1.4 protection relays
TECSYSTEM S.r.l ®
FAULT DIAGNOSTIC
CAUSES AND REMEDIES
Monitoring unit doesn’t turn on, even if there is
power supply and the terminals are fed.
Connector not well placed inside its seat. Connec-
tion cables are not tightened in the terminal. Burnt
out feeder.
Take out and give supply again.
One of 8 channels is in FAULT for FOC/FCC
1) Check Pt100 sensor connections: possible de-
fective sensor.
Replace the damaged sensor.
2) Number of channels programmation different to
number of sensors connected.
Repeat programmation.
When turning on, indication “ECH” appears.
A strong disturbance damaged the stored data.
Please refer to paragraph 8.
If this problem should persist, please contact
TEC-
SYSTEM S.r.l Technical Department.
All the sensors are in FCC.
Wrong sensor connections. Terminal box connected
inside out.
Check connections and terminal box.
Temperature indicated by one or more channel is
wrong.
Contact TECSYSTEM S.r.l. Technical Department.
Sudden trip of main switch. Temperature is on
standard levels. Just a channel caused the trip.
Verify through T.MAX function possible defective
sensors.
Replace the sensor. Check the measuring signal
terminal boxes.
23) NOTES ON FCD FUNCTION
NT device series have an innovatory control function combined with the Pt100 probes dynamic
state.
If a thermometric probe should by chance break down, the defect is highlighted with a fast in-
crease of its own resistance and therefore of the temperature recorded by the monitoring device.
It’s obvious that this increase is not directly resulting from the power increase of the machine to
be protected, whether it is a motor or a dry or encapsulated transformer.
Therefore it is necessary to know the state of the probe and send a Fault signal instead of an
Alarm signal or, worse still, a Trip signal.
In case of temperature control on electrical motors, the fast rise in temperature could be caused
by the working with a stalled rotor and not by a defective probe; in this case Fault relay, once
energised, makes clear this anomalous condition for motor working.
Activating FCD function it is possible to have, on contacts 7-8-9, a Fault signal when temperature
recorded by a Pt100 rises with a speed higher than
“n” °C/sec
(loadable from 1 to 30).
According to the loaded value, you can have a different sensitivity which can be useful for differ-
ent applications:
-
from 1 to 10: high sensitivity, for instance useful to immediately detect stalled of a motor rotor.
-
From 10 to 20: average sensitivity, useful to get information relevant to possible noises which
affect probe reading, connection problems or defective probes.
-
From 20 to 30: low sensitivity, useful for applications where a higher sensitivity could cause a
fault for unwanted FCD’s.
-
With “no” FCD function is disabled.
When a channel is in Fault for FCD, relevant Alarm and Trip signalling are inhibited in order to
report just the anomaly for the too fast rise in temperature.
Press Reset to cancel FCD signalling for all the channels and to reset relays fault.
