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7. OPERATION AND MAINTENANCE
38
Where no remote reset is fitted, the LED signals must be reset each time the
relay picks up
(providing the signals are in operation, i.e. main processing
unit code FAl). Please refer to Section 3.11 for main processing units with
PCB 8 ace. to HESG 440 718
The relay continues to operate correctly
whether the signals are reset or not, but the signals may no longer be related
to the fault concerned.
The relay requires no special maintenance. However, as is usual with all safety
systems, it should be tested at regular intervals. This can be carried out as
described in Section 6.5.
The test buttons on the frontplat.e permit a simple functional test to be carried
out with the relay connected to load quantities. The latter can also be measured
at the test sockets on the front.plate. Furthermore the tripping circuit inclu-
ding the circuit-breaker can be tested with input transformer units with oart
number HESG 440 754 resp. 441 721 and main processing unit with PCB 8 ace. to
HESG 440 718.
Since the simple tests above can be carried out at relatively short intervals,
comprehensive testing with a test set is only necessary at two-yearly intervals.
But quantitive testing is essential after this period regardless of whether the
relay is equipped with a test socket XX91 or not. Where it is not, either
signals must be injected at the terminals after appropriately isolating the main
c. t 's and p. t' s, or the plug-in uni ts can be withdrawn and inserted into a
separate equipment rack wired to the test set.
7.1
Ancillaries and spares
When ordering ancillaries and spares, it is essential that the type
and serial number of the unit for which they are intended be stated.
If a number of identical relays are installed in a plant, we recommend
stocking spare units.
Spares must be stored in a clean dry room at moderate temperatures. It
is further recommended that spares also be tested at the same time as
the periodic testing of the protective equipment in operation, i.e.
every one or two years.
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