26
6.6.3 Measurement of the ac operating currents of the modules
Monitor the ac input current by connecting an ammeter in series with one input
terminal and the source. This test should be done at the following input voltages:
63.5V on 57/70V version of MVTU 11 & MVTU 12
110V on 100/120V version of MVTU 11 & MVTU 12
250V on 220/250V version of MVTU 11 & MVTU 12
415V on 380/440V version of MVTU 11 & MVTU 12
63.5V on 57/120V version of MVTU 13 & MVTU 18
The current through the transformer primary should be approximately 6mA.
If the measured current is zero, suspect an open circuit primary winding, series
resistor or connection.
If the measured current exceeds 8mA, check that the external dropper resistors are
correctly fitted on the 220/250V and the 380/440V versions. If they are correctly
fitted, then the primary windings may be shorted together – return the module for
repair.
6.7 Calibration information
All relays are supplied precalibrated. The 220/250V and the 380/440V ac
versions of the MVTU 11 and 12 are calibrated with the external dropper resistors,
Rext 2, fitted on the resistor assembly supplied with the module. If any external ac
series resistor or the printed circuit board assembly itself is exchanged, the relay will
require recalibration. The dc series dropper resistor Rext 1 may be exchanged
without affecting the relay calibration.
6.8 Repair and replacements
The instructions given enable the detection of faults to sub-assembly level. It is
recommended that any fault on the pcb should be rectified by replacement of the
complete board. However, if any component is replaced, then the relay must be
recalibrated.
It is recommeded that the module is returned to ALSTOM T&D Protection and Control
Ltd for recalibration.
Should the need arise for the equipment to be returned to ALSTOM T&D Protection &
Control Ltd for repair, then the form at the back of this manual should be completed
and sent with the equipment together with a copy of any commissioning test results.
6.9 Repair of trip indicator on MVTU 11, MVTU 12 and MVTU 13 relays
If the trip indication fails then it may be necessary to replace the mechanical flag unit
or LED indicator pcb depending on which is fitted,
On the MVTU 18 only, the LED trip indication and the output relays are fitted to pcb
ZJ1060 which should be replaced complete in the event of trip indication failure.
6.10 Repair and replacement of miniature pcb mounted relay and flag mechanism (where
fitted)
The miniature relay cannot be repaired. If it is proved to be operating incorrectly, it
must be replaced. The flag assembly can be reset, or damaged parts replaced as
required. If any part of the flag/relay assembly is disturbed, the settings of the
assembly must be checked and adjustments made where necessary.
To Next Page
Loading...
