GE DFF1000 Series, Instructions Manual, Page: 42 / 59

GEK – 106166B
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8. 8. 8. 8. INSTALLATION AND MAINTENANCE INSTALLATION AND MAINTENANCE INSTALLATION AND MAINTENANCE INSTALLATION AND MAINTENANCE
8.1 INSTALLATION
The place where the relay is to be installed must be clean, dry, free of dust and vibrations, and well illuminated to
facilitate inspection and tests.
The relay must be mounted on a vertical surface. Figure 2 represents the drilling diagram in order to do the panel
cut out
As DFF design is based on state-of-the-art digital technology and the manufacturing is done under severe control
conditions with sophisticated high accuracy equipment, it is completely unnecessary to recalibrate the relay.
8.2 GROUND CONNECTION FOR SAFETY AND PERTURBATION REMOVAL.
A12 ground terminal (see figure 6) must be connected to ground in order to get a right operation of the
perturbation removal filters included in the system. For securing the maximum protection, this connection must be
as short as possible (preferably 25 cm or less). In this way, the capacitors internally connected between outputs
and ground deflect the high frequency perturbations directly to ground without crossing the electronic circuits, so
that these circuits are perfectly protected.
Besides, physical safety of the staff who handle the relay is guaranteed by means of this connection, as the whole
chassis is grounded.
8.3 MAINTENANCE
Due to the primary role that protection relays have in any installation, it is recommended that a periodic test
program is followed. As the intervals between these tests vary for different types of relays and installations, as well
as for the experience of the user performing the tests, and given that this equipment provides self-diagnosis
functions that allow to detect immediately failures of the circuitry with the only help of the keyboard and the
display, it is recommended to test the relay at intervals of 2 years or more. Although this self-diagnosis capability
does not reduce the average time between failures, it increases the availability of the protection thanks to the
possibility of drastic reduction of the average repairing time which involves the failure detection and the repairing
too.
The group of tests that can be done to verify the whole operativity of DFF equipment is deeply described in
EVALUATION TESTS chapter
The majority of the protection and communication functions are integrated in two different EPROM based
programs, because of this the rate of failures is significantly lower to the ones of previous designs
(electromechanical or static analog relays). Besides this there is no need of relay recalibration after a few years of
use.
Possible failures of the communication microprocessor do not affect to the protection functions, which are
implemented by means of a dedicated microprocessor.